F5 NETWORKS INC
S-1, 1999-09-09
COMPUTER INTEGRATED SYSTEMS DESIGN
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<PAGE>
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON SEPTEMBER 9, 1999
                                                       REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 --------------

                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                                 --------------

                               F5 NETWORKS, INC.

             (Exact name of registrant as specified in its charter)

<TABLE>
<S>                              <C>                            <C>
          WASHINGTON                         3570                  91-1714307
 (State or other jurisdiction    (Primary Standard Industrial   (I.R.S. Employer
              of                 Classification Code Number)     Identification
incorporation or organization)                                      Number)
</TABLE>

                        200 FIRST AVENUE WEST, SUITE 500
                           SEATTLE, WASHINGTON 98119
                                 (206) 505-0800

  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)

                                  JOANN REITER
                         GENERAL COUNSEL AND SECRETARY
                               F5 NETWORKS, INC.
                        200 FIRST AVENUE WEST, SUITE 500
                           SEATTLE, WASHINGTON 98119
                                 (206) 505-0800

 (Name, address, including zip code, and telephone number, including area code,
                             of agent for service)
                                ----------------

                                   COPIES TO:

        DAVID R. WILSON, ESQ.                      BROOKS STOUGH, ESQ.
   HELLER EHRMAN WHITE & MCAULIFFE               GUNDERSON DETTMER STOUGH
         6100 COLUMBIA CENTER              VILLENEUVE FRANKLIN & HACHIGIAN, LLP
           701 FIFTH AVENUE                       155 CONSTITUTION DRIVE
          SEATTLE, WA 98104                    MENLO PARK, CALIFORNIA 94025
            (206) 447-0900                            (650) 321-2400

                                ----------------

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
   As soon as practicable after the Registration Statement becomes effective.
                                ----------------

    If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act,
check the following box. / /

    If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, check the following box and
list the Securities Act registration statement number of the earlier effective
registration statement for the same offering. / /

    If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
number for the same offering. / /

    If this Form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration number of the earlier effective registration statement for the same
offering. / /

    If delivery of the prospectus is expected to be made pursuant to Rule 434,
check the following box. / /
                                ----------------

                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                                        PROPOSED MAXIMUM    PROPOSED MAXIMUM
             TITLE OF EACH CLASS OF                   AMOUNT TO BE     OFFERING PRICE PER      AGGREGATE           AMOUNT OF
           SECURITIES TO BE REGISTERED               REGISTERED (1)        SHARE (2)       OFFERING PRICE (2)   REGISTRATION FEE
<S>                                                <C>                 <C>                 <C>                 <C>
Common Stock, no par value.......................      2,300,000             $65.50           $150,650,000          $41,881
</TABLE>

(1) Includes 300,000 shares which the underwriters have the option to purchase
    to cover over-allotments, if any.

(2) Determined in accordance with Rule 457(c) under the Securities Act of 1933,
    as amended, as the average of the bid and asked price of the common stock on
    the Nasdaq National Market on September 2, 1999.
                                ----------------

    THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT THAT SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933, AS AMENDED, OR UNTIL THE REGISTRATION STATEMENT
SHALL BECOME EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID
SECTION 8(a), MAY DETERMINE.

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
                 SUBJECT TO COMPLETION, DATED SEPTEMBER 9, 1999
THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED.
UNDERWRITERS MAY NOT CONFIRM SALES OF THESE SECURITIES UNTIL THE REGISTRATION
STATEMENT FILED WITH THE SECURITIES AND EXCHANGE COMMISSION BECOMES EFFECTIVE.
THIS PROSPECTUS IS NOT AN OFFER TO SELL THESE SECURITIES AND IT IS NOT
SOLICITING OFFERS TO BUY THESE SECURITIES IN ANY STATE WHERE THE OFFER OR SALE
IS NOT PERMITTED.
<PAGE>
PROSPECTUS

                                2,000,000 SHARES

                                     [LOGO]

                                  COMMON STOCK

    This is an offering of common stock by F5 Networks, Inc. Of the 2,000,000
shares of common stock being sold in this offering, 500,000 shares are being
sold by F5 and 1,500,000 shares are being sold by the selling shareholders. F5
will not receive any of the proceeds from the sale of shares by the selling
shareholders. Our common stock trades on the Nasdaq National Market under the
symbol FFIV. On September 8, 1999, the last reported sale price of our common
stock on the Nasdaq National Market was $69.50 per share. See "Market Price of
the Common Stock."

                                 --------------

<TABLE>
<CAPTION>
                                                                       PER SHARE     TOTAL
                                                                      -----------  ----------
<S>                                                                   <C>          <C>
Public offering price...............................................   $           $
Underwriting discounts and commissions..............................   $           $
Proceeds to F5, before expenses.....................................   $           $
Proceeds to the selling shareholders, before expenses...............   $           $
</TABLE>

    F5 and certain shareholders have granted the underwriters an option for a
period of 30 days to purchase up to 300,000 additional shares of common stock.

                                 --------------

    INVESTING IN THE COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. SEE "RISK
FACTORS" BEGINNING ON PAGE 7.

                                 -------------

    NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE
ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

HAMBRECHT & QUIST
           BANCBOSTON ROBERTSON STEPHENS
                       BEAR, STEARNS & CO. INC.
                                   DAIN RAUSCHER WESSELS     A DIVISION OF DAIN
RAUSCHER INCORPORATED

September  , 1999
<PAGE>

EDGAR Artwork Descriptions

Inside Front Cover of Prospectus:

    Caption 1:
    Internet Quality Control

    Caption 2:
    Availability
    Performance
    Manageability

    Graphic depicting F5 Networks logo surrounded by names and logos
    of its current products and product under development:

        Upper left hand quadrant caption:
        BIG/ip logo and name

        Upper right hand quadrant caption:
        3DNS logo and name

        Lower left hand quadrant caption:
        Global/SITE logo with caption "under development" underneath

        Lower right hand quadrant caption:
        see/IT logo and name

    F5 Networks logo

Inside Gatefold:

Upper left hand corner:

    F5 Networks logo

    Title: Availability, performance and control for mission-critical
    Internet sites

    Graphic depicting the role of the BIG/ip Controller, 3DNS Controller, see/IT
    Network Manager and global/SITE Controller in an organization's
    Internet-based environment. In the graphic, an organization's Internet and
    file servers are shown in multiple locations (Seattle, New York, London and
    Tokyo) with the F5 products placed between the Internet servers and the
    organization's routers. Dashed lines illustrate the interaction of the F5
    products within the organization's network.

    Caption 1 - upper left hand corner:
       BIG/ip Controller name and logo
       An intelligent load balancer for local area networks

    Caption 2 - upper right hand corner
       3DNS Controller name and logo
       An intelligent load balancer for wide area networks

    Caption 3 - lower right hand corner
       See/IT Network Manager name and logo
       A traffic analysis and network management software application for
       BIG/ip and 3DNS

    Caption 4 - lower left hand corner:
       Global/SITE Controller name and logo with caption "Under Development"
       underneath
       File replication and synchronization controller for managing content
       across geographically dispersed Internet sites

Inside Back Cover:

    F5 Networks logo with the following words underneath:

    F5 Networks, Inc. provides integrated Internet traffic management solutions
    designed to improve the availability and performance of mission-critical
    Internet-based servers and applications
<PAGE>
                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                    PAGE
                                                    ----
<S>                                                 <C>
Prospectus Summary................................    4

Risk Factors......................................    7

Forward Looking Statements........................   13

Use of Proceeds...................................   14

Dividend Policy...................................   14

Market Price of the Common Stock..................   14

Capitalization....................................   15

Selected Financial Data...........................   16

Management's Discussion and Analysis of Financial
  Condition and Results of Operations.............   17

Business..........................................   26

Management........................................   37

Certain Transactions..............................   46

Principal and Selling Shareholders................   48

Description of Capital Stock......................   50

Shares Eligible for Future Sale...................   53

Underwriting......................................   55

Legal Matters.....................................   56

Experts...........................................   56

Additional F5 Information.........................   56

Index to Financial Statements.....................  F-1
</TABLE>

    Information contained on F5's Web site does not constitute part of this
prospectus.

    BIG/ip-Registered Trademark-, the F5 logo, and 3DNS-Registered Trademark-
are registered United States trademarks of F5. This prospectus also contains
trademarks and tradenames of other companies.

                                       3
<PAGE>
                               PROSPECTUS SUMMARY

    THIS SUMMARY HIGHLIGHTS SELECTED INFORMATION CONTAINED ELSEWHERE IN THIS
PROSPECTUS. THIS SUMMARY MAY NOT CONTAIN ALL OF THE INFORMATION THAT YOU SHOULD
CONSIDER BEFORE INVESTING IN OUR COMMON STOCK. YOU SHOULD READ THE ENTIRE
PROSPECTUS CAREFULLY, INCLUDING "RISK FACTORS" AND THE FINANCIAL STATEMENTS,
BEFORE MAKING AN INVESTMENT DECISION.

                                  F5 NETWORKS

    F5 is a leading provider of integrated Internet traffic management solutions
designed to improve the availability and performance of mission-critical
Internet-based servers and applications. Our products monitor and manage local
and geographically dispersed servers and intelligently direct traffic to the
server best able to handle a user's request. Our products are designed to help
prevent system failure and provide timely responses to user requests and data
flow. Our BIG/ip-Registered Trademark- and 3DNS-Registered Trademark-
Controllers, when combined with our see/IT-TM- Network Manager, help
organizations optimize their network server availability and performance and
cost-effectively manage their Internet infrastructure. Our solutions are used by
organizations who rely on the Internet as a fundamental component of their
business. Our customers include Internet service providers, such as Exodus
Communications, Frontier GlobalCenter, PSINet, and MCI WorldCom, e-commerce
companies and many other organizations that employ high-traffic Internet sites.
We have sold our products to over 600 end-customers as of August 31, 1999.

    The Internet has emerged as a critical commerce and communications platform
for businesses and consumers worldwide. The growing use of the Internet is
causing the complexity and volume of Internet traffic to increase dramatically.
According to UUNet, Internet traffic doubles every 100 days. The widespread
proliferation in the use and importance of the Internet has strained many
organizations' network infrastructures. In response to dramatic increases in
Internet use and traffic, organizations are expanding server capacity and are
deploying redundant servers. According to IBM, servers are being connected to
the Internet at a rate of 53,000 per month. While additional and redundant
servers help address the rapidly increasing traffic, they also increase an
organization's need for sophisticated Internet traffic management tools to
manage the availability and performance of its servers and applications.

    We believe that our products deliver Internet quality control by providing
the following key benefits:

    - HIGH SYSTEM AVAILABILITY. Our products help prevent system failure by
      quickly detecting server, application and network failures and directing
      traffic to functioning servers and applications.

    - INCREASED PERFORMANCE. Our products intelligently direct user requests to
      the server with the fastest response time by monitoring server and
      application response time and verifying content.

    - COST-EFFECTIVE SCALABILITY. Our products help optimize existing server
      capacity and allow the transparent addition of servers into an existing
      network.

    - EASIER NETWORK MANAGEABILITY. Our products collect information that can be
      used to facilitate network management and planning from a central
      location.

    - ENHANCED NETWORK CONTROL. Our products enable organizations to prioritize
      and manage network traffic based on user-defined criteria to meet their
      specific needs.

    We plan to continue expanding our suite of products to provide complete,
integrated Internet traffic management solutions that further optimize the
availability and performance of network servers and applications. For example,
we are currently developing our global/SITE-TM- Controller to ensure data
integrity by automatically synchronizing content across local and geographically
dispersed network servers. We also plan to continue investing significant
resources to expand our direct sales force and further develop our indirect
sales channels through leading industry resellers, original equipment
manufacturers, systems integrators, Internet service providers and other channel
partners. Finally, we intend to continue investing in our professional services
group in order to provide the installation, training and support services
required to help our customers optimize their use of our Internet traffic
management solutions.

    Our headquarters are located at 200 First Avenue West, Suite 500, Seattle,
Washington 98119, our telephone number is (206) 505-0800 and our Web site
address is www.F5.com.

                                       4
<PAGE>
                                  THE OFFERING

<TABLE>
<S>                                 <C>
Common stock offered by F5........  500,000 shares

Common stock offered by the
  selling shareholders............  1,500,000 shares

Common stock to be outstanding
  after this offering.............  18,626,667 shares (1)

Use of proceeds...................  For working capital and general corporate purposes. See
                                    "Use of Proceeds."

Nasdaq National Market symbol.....  FFIV
</TABLE>

- ------------------------

(1) The number of shares of common stock to be outstanding after this offering
    is based on the number of shares outstanding as of August 31, 1999 and does
    not include the following:

    - 2,440,405 shares subject to options outstanding as of August 31, 1999 with
      a weighted average exercise price of $3.76 per share;

    - 3,559,598 additional shares that could be issued under our stock option
      plans and stock purchase plan; and

    - 2,212,500 shares that could be issued upon exercise of warrants
      outstanding as of August 31, 1999 with a weighted average exercise price
      of $0.75 per share.

                                 --------------

    ALL INFORMATION IN THIS PROSPECTUS RELATING TO OUTSTANDING SHARES OF F5
COMMON STOCK AND OPTIONS OR WARRANTS TO PURCHASE F5 COMMON STOCK IS BASED UPON
INFORMATION AS OF AUGUST 31, 1999. UNLESS OTHERWISE INDICATED, THE INFORMATION
THROUGHOUT THIS PROSPECTUS DOES NOT TAKE INTO ACCOUNT THE POSSIBLE ISSUANCE OF
ADDITIONAL SHARES OF COMMON STOCK TO THE UNDERWRITERS PURSUANT TO THEIR
OVER-ALLOTMENT OPTION.

    PLEASE SEE "CAPITALIZATION" FOR A MORE COMPLETE DISCUSSION REGARDING THE
OUTSTANDING SHARES OF F5 COMMON STOCK AND OPTIONS OR WARRANTS TO PURCHASE F5
COMMON STOCK AND OTHER RELATED MATTERS.

                                       5
<PAGE>
                         SUMMARY FINANCIAL INFORMATION
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
                                                                           FISCAL YEAR ENDED    NINE MONTHS ENDED JUNE
                                                  PERIOD FROM FEBRUARY       SEPTEMBER 30,               30,
                                                 26, 1996 (INCEPTION) TO  --------------------  ----------------------
                                                   SEPTEMBER 30, 1996       1997       1998                    1999
                                                 -----------------------  ---------  ---------     1998      ---------
                                                                                                -----------
                                                                                                (UNAUDITED)
<S>                                              <C>                      <C>        <C>        <C>          <C>
STATEMENT OF OPERATIONS DATA:
  Net revenues.................................         $       2         $     229  $   4,889   $   2,981   $  14,063
  Loss from operations.........................              (348)           (1,428)    (3,668)     (2,277)     (6,864)
  Net loss.....................................         $    (330)        $  (1,456) $  (3,672)  $  (2,298)  $  (6,678)
  Net loss per share--basic and diluted........         $   (0.06)        $   (0.24) $   (0.60)  $   (0.37)  $   (0.88)
  Weighted average shares--basic and diluted
    (1)........................................             5,932             6,000      6,086       6,135       7,582
  Pro forma net loss per share (unaudited):
    Net loss per share--basic and diluted......                                      $   (0.26)              $   (0.45)
                                                                                     ---------               ---------
                                                                                     ---------               ---------
    Weighted average shares--basic and diluted
      (1)......................................                                         14,201                  14,923
                                                                                     ---------               ---------
                                                                                     ---------               ---------
</TABLE>

<TABLE>
<CAPTION>
                                                                           JUNE 30, 1999
                                                                     --------------------------
                                                                      ACTUAL    AS ADJUSTED (2)
                                                                     ---------  ---------------
<S>                                                                  <C>        <C>
BALANCE SHEET DATA:
  Cash and cash equivalents........................................  $  26,948     $  59,510
  Working capital..................................................     26,774        59,436
  Total assets.....................................................     36,486        69,148
  Shareholders' equity.............................................     28,905        61,568
</TABLE>

- ------------------------

(1) See Note 2 of notes to financial statements for an explanation of the
    determination of the number of shares used in computing per share data.

(2) Adjusted to reflect the sale by F5 of 500,000 shares of common stock at an
    assumed public offering price of $69.50 per share and the application of the
    estimated net proceeds after deducting estimated underwriting discounts and
    commissions and our offering expenses. See "Use of Proceeds" and
    "Capitalization."

                                       6
<PAGE>
                                  RISK FACTORS

    YOU SHOULD CAREFULLY CONSIDER THE FOLLOWING RISK FACTORS AND ALL OTHER
INFORMATION CONTAINED IN THIS PROSPECTUS BEFORE PURCHASING OUR COMMON STOCK.
INVESTING IN OUR COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. ANY OF THE
FOLLOWING RISKS MAY SERIOUSLY HARM OUR BUSINESS AND RESULTS OF OPERATIONS AND
MAY RESULT IN A COMPLETE LOSS OF YOUR INVESTMENT.

OUR LIMITED OPERATING HISTORY MAKES IT DIFFICULT TO EVALUATE OUR PROSPECTS.

    We were founded in February 1996 and have a limited operating history, which
makes an evaluation of our prospects difficult. Because of our limited operating
history, we have limited insight into trends that may emerge and affect our
business. In addition, the revenues and income potential of our business and
market are unproven. An investor in our common stock must consider the
challenges, expenses and difficulties we face as an early stage company in a new
and rapidly evolving market.

OUR QUARTERLY OPERATING RESULTS ARE VOLATILE AND MAY CAUSE OUR STOCK PRICE TO
  FLUCTUATE.

    Our quarterly operating results have varied significantly in the past and
will vary significantly in the future, which makes it difficult for us to
predict our future operating results. In particular, we anticipate that the size
of customer orders may increase as we continue to focus on larger business
accounts and sales to governmental entities. A delay in the recognition of
revenue, even from just one account, may have a significant negative impact on
our results of operations for a given period. In the past, a significant portion
of our sales have been realized near the end of a quarter. Accordingly, a delay
in an anticipated sale past the end of a particular quarter may negatively
impact our results of operations for that quarter. Furthermore, we base our
decisions regarding our operating expenses on anticipated revenue trends, and
our expense levels are relatively fixed. Consequently, if revenue levels fall
below our expectations, our net income (loss) will decrease (increase) because
only a small portion of our expenses vary with our revenues. See "Management's
Discussion and Analysis of Financial Condition and Results of Operations."

    We believe that period-to-period comparisons of our results of operations
are not meaningful and should not be relied upon as indicators of future
performance. Our operating results will likely be below the expectations of
securities analysts and investors in some future quarter or quarters. Our
failure to meet these expectations will likely seriously harm the market price
of our common stock.

WE HAVE INCURRED LOSSES AND WE EXPECT TO INCUR SIGNIFICANT FUTURE OPERATING
  EXPENSES AND LOSSES.

    We have experienced operating losses in each quarterly and annual period
since inception. We incurred net losses of $330,000 for the period from February
26, 1996, inception, to September 30, 1996, $1.5 million for the year ended
September 30, 1997, $3.7 million for the year ended September 30, 1998, and $6.7
million for the nine months ended June 30, 1999.

    We intend to substantially increase our operating expenses. As a result, we
will need to generate significant increases in our quarterly net revenues to
achieve and maintain profitability. Although our net revenues have grown in
recent quarters, we may not be able to sustain these growth rates or achieve or
sustain profitability. Our failure to achieve and sustain profitability will
seriously harm our business and results of operations. See "Selected Financial
Data" and "Management's Discussion and Analysis of Financial Condition and
Results of Operations."

OUR SUCCESS DEPENDS ON SALES OF OUR BIG/IP-REGISTERED TRADEMARK- CONTROLLER.

    We currently derive approximately 73% of our net revenues from sales of our
BIG/ip Controller. In addition, we expect to derive a significant portion of our
net revenues from sales of BIG/ip in the future. Implementation of our strategy
depends upon BIG/ip being able to solve critical network availability and

                                       7
<PAGE>
performance problems of our customers. If BIG/ip is unable to solve these
problems for our customers, our business and results of operations will be
seriously harmed.

OUR SUCCESS DEPENDS ON OUR TIMELY DEVELOPMENT OF NEW PRODUCTS AND FEATURES.

    We expect the Internet traffic management market to be characterized by
rapid technological change, frequent new product introductions, changes in
customer requirements and evolving industry standards. We are currently
developing our global/SITE-TM- Controller and new features for our existing
products. We expect to continue to develop new products and new product features
in the future. If we fail to develop and deploy new products and new product
features on a timely basis, our business and results of operations may be
seriously harmed. See "Business--Product Development."

WE MAY NOT BE ABLE TO COMPETE EFFECTIVELY IN THE EMERGING INTERNET TRAFFIC
  MANAGEMENT MARKET.

    Our markets are new, rapidly evolving and highly competitive, and we expect
competition to persist and intensify in the future. Our principal competitors in
the Internet traffic management market include Cisco Systems, Alteon WebSystems,
ArrowPoint Communications, HydraWeb Technologies, RadWare and Resonate. We
expect to continue to face additional competition as new participants enter the
Internet traffic management market. In addition, larger companies with
significant resources, brand recognition and sales channels may form alliances
with or acquire competing Internet traffic management solutions and emerge as
significant competitors. Potential competitors may bundle their products or
incorporate an Internet traffic management component into existing products in a
manner that discourages users from purchasing our products. Potential customers
may also choose to purchase additional servers instead of our products. See
"Business--Competition."

WE MAY NOT BE ABLE TO SUPPORT OUR RAPID GROWTH EFFECTIVELY.

    Since the introduction of our product line, we have experienced a period of
rapid growth and expansion which has placed, and continues to place, a
significant strain on all of our resources. From September 30, 1997 to August
31, 1999, we increased the number of our employees from 20 to 178. We expect our
growth to continue to strain our management, operational and financial
resources. For example, we may not be able to install adequate financial control
systems in an efficient and timely manner, and our current or planned
information systems, procedures and controls may be inadequate to support our
future operations. The difficulties associated with installing and implementing
new systems, procedures and controls may place a significant burden on our
management and our internal resources. Our inability to manage growth
effectively may seriously harm our business and results of operations.

OUR EXPANSION INTO INTERNATIONAL MARKETS MAY NOT SUCCEED.

    We intend to expand into international markets. We have only limited
experience in marketing, selling and supporting our products internationally.
International sales represented 6.6% of our net revenues for the year ended
September 30, 1997, 3.5% for the year ended September 30, 1998 and 7.1% for the
nine months ended June 30, 1999. We have recently engaged sales personnel in the
United Kingdom and in Germany. Our continued growth will require further
expansion of our international operations in selected countries in the European
and Asia Pacific markets. If we are unable to expand our international
operations successfully and in a timely manner, our business and results of
operations may be seriously harmed. Such expansion may be more difficult or take
longer than we anticipate, and we may not be able to successfully market, sell,
deliver and support our products internationally.

WE MAY NOT BE ABLE TO SUSTAIN OR DEVELOP NEW DISTRIBUTION RELATIONSHIPS.

    Our sales strategy requires that we establish multiple distribution channels
in the United States and internationally through leading industry resellers,
original equipment manufacturers, systems integrators,

                                       8
<PAGE>
Internet service providers and other channel partners. We have a limited number
of agreements with companies in these channels, and we may not be able to
increase our number of distribution relationships or maintain our existing
relationships. One of our resellers, Exodus Communications, Inc., accounted for
21.7% of our net revenues for the nine months ended June 30, 1999 and 29.4% of
our accounts receivable balance at June 30, 1999. Our inability to effectively
establish our indirect sales channels will seriously harm our business and
results of operations.

OUR SUCCESS DEPENDS ON OUR ABILITY TO ATTRACT, TRAIN AND RETAIN QUALIFIED
  MARKETING AND SALES, PROFESSIONAL SERVICES AND CUSTOMER SUPPORT PERSONNEL.

    Our products require a sophisticated marketing and sales effort targeted at
several levels within a prospective customer's organization. We have recently
expanded our sales force and plan to hire additional sales personnel for direct
sales and to develop leads for our indirect sales channels. Competition for
qualified sales personnel is intense, and we might not be able to hire the kind
and number of sales personnel we are targeting. Our inability to retain and hire
qualified sales personnel may seriously harm our business and results of
operations.

    We currently have a small professional services and customer support
organization and will need to increase our staff to support new customers and
the expanding needs of existing customers. The installation of Internet traffic
management solutions, the integration of these solutions into existing networks
and the ongoing support can be complex. Accordingly, we need highly-trained
professional services and customer support personnel. Hiring professional
services and customer support personnel is very competitive in our industry due
to the limited number of people available with the necessary technical skills
and understanding of our products. Our inability to attract, train or retain the
number of highly qualified professional services and customer support personnel
that our business needs may seriously harm our business and results of
operations.

WE DEPEND ON OUR KEY PERSONNEL AND THE LOSS OF ANY KEY PERSONNEL MAY HARM OUR
  BUSINESS AND RESULTS OF OPERATIONS.

    Our success depends to a significant degree upon the continued contributions
of our key management, product development, sales and marketing and finance
personnel, many of whom will be difficult to replace. In particular, we rely on
our President and Chief Executive Officer, Jeffrey Hussey. The loss of services
of any of our key personnel, especially the services of Mr. Hussey, may
seriously harm our business and results of operations. We do not have employment
contracts with any of our key personnel.

IT IS DIFFICULT TO PREDICT OUR FUTURE OPERATING RESULTS BECAUSE WE HAVE AN
  UNPREDICTABLE SALES CYCLE.

    We are unable to predict our sales cycle because we have limited experience
selling our products. Historically, our sales cycle has ranged from
approximately two to three months. Sales of BIG/ip, 3DNS and our see/IT-TM-
Network Manager require us to educate potential customers on their use and
benefits. The sale of our products is subject to delays from the lengthy
internal budgeting, approval and competitive evaluation processes that large
corporations and governmental entities may require. For example, customers
frequently begin by evaluating our products on a limited basis and devote time
and resources to testing our products before they decide whether or not to
purchase. Customers may also defer orders as a result of anticipated releases of
new products or enhancements by us or our competitors. As a result, our products
have an unpredictable sales cycle that contributes to the uncertainty of our
future operating results.

                                       9
<PAGE>
THE AVERAGE SELLING PRICES OF OUR PRODUCTS MAY DECREASE, WHICH MAY NEGATIVELY
  IMPACT GROSS PROFITS.

    We anticipate that the average selling prices of our products will decrease
in the future in response to competitive pricing pressures, increased sales
discounts, new product introductions by us or our competitors or other factors.
Therefore, in order to maintain our gross profits, we must develop and introduce
new products and product enhancements on a timely basis and continually reduce
our product costs. Our failure to do so will cause our net revenue and gross
profits to decline, which will seriously harm our business and results of
operations. In addition, we may experience substantial period-to-period
fluctuations in future operating results due to the erosion of our average
selling prices.

OUR BUSINESS MAY BE HARMED IF OUR CONTRACT MANUFACTURERS ARE NOT ABLE TO PROVIDE
  US WITH ADEQUATE SUPPLIES OF OUR PRODUCTS.

    We rely on third party contract manufacturers to assemble our products. We
outsource the manufacturing of our pre-configured, industry-standard hardware
platforms to primarily two contract manufacturers, Micro Standard Distributors
and Unisoft, who assemble these hardware platforms to our specifications. The
inability of our contract manufacturers to provide us with adequate supplies of
our products or the loss of one or more of our contract manufacturers may cause
a delay in our ability to fulfill orders while we obtain a replacement
manufacturer and may seriously harm our business and results of operations.

    If the demand for our products grows, we will need to increase our material
purchases, contract manufacturing capacity and internal test and quality
functions. Any disruptions in product flow may limit our revenue, may seriously
harm our competitive position and may result in additional costs or cancellation
of orders by our customers. See "Business--Manufacturing."

OUR BUSINESS COULD SUFFER IF THERE ARE ANY INTERRUPTIONS OR DELAYS IN THE SUPPLY
  OF HARDWARE COMPONENTS FROM OUR THIRD-PARTY SOURCES.

    We currently purchase several hardware components used in the assembly of
our products from limited sources. Lead times for these components vary
significantly. Any interruption or delay in the supply of any of these hardware
components, or the inability to procure a similar component from alternate
sources at acceptable prices within a reasonable time, will seriously harm our
business and results of operations. See "Business--Manufacturing."

UNDETECTED SOFTWARE ERRORS MAY SERIOUSLY HARM OUR BUSINESS AND RESULTS OF
  OPERATIONS.

    Software products frequently contain undetected errors when first introduced
or as new versions are released. We have experienced these errors in the past in
connection with new products and product upgrades. We expect that these errors
will be found from time to time in new or enhanced products after commencement
of commercial shipments. These problems may cause us to incur significant
warranty and repair costs, divert the attention of our engineering personnel
from our product development efforts and cause significant customer relations
problems. We may also be subject to liability claims for damages related to
product errors. While we carry insurance policies covering this type of
liability, these policies may not provide sufficient protection should a claim
be asserted. A material product liability claim may seriously harm our business
and results of operations.

    Our products must successfully operate with products from other vendors. As
a result, when problems occur in a network, it may be difficult to identify the
source of the problem. The occurrence of software errors, whether caused by our
products or another vendor's products, may result in the delay or loss of market
acceptance of our products. The occurrence of any of these problems may
seriously harm our business and results of operations.

                                       10
<PAGE>
WE MAY NOT ADEQUATELY PROTECT OUR INTELLECTUAL PROPERTY AND OUR PRODUCTS MAY
  INFRINGE ON THE INTELLECTUAL PROPERTY RIGHTS OF THIRD PARTIES.

    We rely on a combination of copyright, trademark and trade secret laws and
restrictions on disclosure to protect our intellectual property rights. Despite
our efforts to protect our proprietary rights, unauthorized parties may attempt
to copy or otherwise obtain and use our products or technology. Monitoring
unauthorized use of our products is difficult, and we cannot be certain that the
steps we have taken will prevent misappropriation of our technology,
particularly in foreign countries where the laws may not protect our proprietary
rights as fully as in the United States. In addition, we have not entered into
non-competition agreements with several of our former employees.

    From time to time, third parties may assert patent, copyright, trademark and
other intellectual property rights claims or initiate litigation against us or
our contract manufacturers, suppliers or customers with respect to existing or
future products. In the event of a successful claim of infringement and our
failure or inability to develop non-infringing technology or license the
infringed or similar technology on a timely basis, our business and results of
operations may be seriously harmed. See "Business--Intellectual Property."

OUR FAILURE AND THE FAILURE OF OUR KEY SUPPLIERS, MANUFACTURERS AND CUSTOMERS TO
  BE YEAR 2000 COMPLIANT MAY NEGATIVELY IMPACT OUR BUSINESS AND RESULTS OF
  OPERATIONS.

    The Year 2000 computer issue creates a significant risk for us in at least
four areas:

    - potential warranty or other claims arising from our products;

    - systems we use to run our business;

    - systems used by our suppliers and contract manufacturers; and

    - the potential reduced spending by other companies on Internet traffic
      management solutions as a result of significant information systems
      spending on Year 2000 remediation or to limit additional changes to their
      systems during the current year.

    A failure in any of these areas to be Year 2000 compliant may seriously harm
our operations. See "Management's Discussion and Analysis of Financial Condition
and Results of Operations--Year 2000 Compliance."

LAWS RELATING TO ENCRYPTED SOFTWARE MAY LIMIT THE MARKETABILITY OF OUR PRODUCTS.

    The encryption technology contained in our products is subject to United
States export controls. These export controls limit our ability to distribute
encrypted software outside of the United States and Canada. While we take
precautions against unlawful exportation, this exportation inadvertently may
have occurred in the past or may occur from time to time in the future,
subjecting us to potential liability and serious harm. We may also encounter
difficulties competing with non-United States producers of products containing
encrypted software, who may both import their products into the United States
and sell products overseas.

WE MAY NEED TO RAISE ADDITIONAL FUNDS, WHICH MAY NOT BE AVAILABLE.

    We expect that the net proceeds from this offering, our existing cash
balances and cash from operations will be sufficient to meet our currently
anticipated working capital and capital expenditure needs for the foreseeable
future. If currently unforeseen events arise, such as a product or technology
acquisition paid for with cash, we may need to raise additional funds, and
additional financing may not be available on favorable terms, if at all.
Further, if we issue additional equity securities, shareholders may experience
dilution, and the new equity securities may have rights, preferences or
privileges senior to those of existing holders of our common stock. If we cannot
raise funds, if needed, on acceptable terms,

                                       11
<PAGE>
we may not be able to develop new products or enhance our existing products,
take advantage of future opportunities or respond to competitive pressures or
unanticipated requirements. This may seriously harm our business and results of
operations. See "Use of Proceeds," "Dilution" and "Management's Discussion and
Analysis of Financial Condition and Results of Operations--Liquidity and Capital
Resources."

OUR EXISTING SHAREHOLDERS WILL BE ABLE TO EXERCISE SIGNIFICANT CONTROL OVER ALL
  MATTERS REQUIRING SHAREHOLDER APPROVAL.

    On completion of this offering, executive officers, directors and their
affiliates and 5% shareholders will beneficially own, in the aggregate,
approximately 60.8% of our outstanding common stock. As a result, these
shareholders will be able to exercise significant control over all matters
requiring shareholder approval, including the election of directors and approval
of significant corporate transactions, which may have the effect of delaying or
preventing a third party from acquiring control over us. See "Principal and
Selling Shareholders."

WE ARE AT RISK OF SECURITIES CLASS ACTION LITIGATION DUE TO OUR EXPECTED STOCK
  PRICE VOLATILITY.

    An active public market price for our common stock may not be maintained in
the future. The market price of our common stock has fluctuated and may continue
to fluctuate significantly in response to a number of factors, some of which are
beyond our control. See "Market Price of the Common Stock." In the past,
securities class action litigation has often been brought against a company
following periods of volatility in the market price of its securities. We may in
the future be the target of similar litigation. Securities litigation may result
in substantial costs and divert management's attention and resources, which may
seriously harm our business and results of operations.

WE HAVE IMPLEMENTED ANTI-TAKEOVER PROVISIONS THAT COULD DELAY OR PREVENT A
  CHANGE IN CONTROL OF F5.

    Provisions of our articles of incorporation and bylaws, as well as
provisions of Washington law, may make it more difficult for a third party to
acquire us, even if doing so would be beneficial to our shareholders. See
"Description of Capital Stock."

SUBSTANTIAL SALES OF SHARES MAY IMPACT THE MARKET PRICE OF OUR COMMON STOCK.

    If our shareholders sell substantial amounts of our common stock, including
shares issued upon the exercise of outstanding options and warrants, the market
price of our common stock may fall. Such sales might also make it more difficult
for us to sell equity or equity-related securities in the future at a time and
price that we deem appropriate. After completion of this offering, we will have
outstanding 18,626,667 shares of common stock, assuming no exercise of
outstanding options or warrants after August 31, 1999. See "Shares Eligible for
Future Sale" and "Underwriting."

WE MAY SPEND THE OFFERING PROCEEDS IN WAYS WITH WHICH OUR SHAREHOLDERS MAY NOT
  AGREE.

    The majority of the net proceeds to the Company of this offering are not
allocated for specific uses and our management can spend most of the proceeds
from this offering in ways with which our shareholders may not agree. We cannot
predict that the proceeds will be invested to yield a favorable return. See "Use
of Proceeds."

                                       12
<PAGE>
                           FORWARD LOOKING STATEMENTS

    Certain statements under the captions "Prospectus Summary," "Risk Factors,"
"Use of Proceeds," "Management's Discussion and Analysis of Financial Condition
and Results of Operations" and "Business," and elsewhere in this prospectus are
"forward-looking statements." These forward-looking statements include, but are
not limited to, statements about our plans, objectives, expectations and
intentions and other statements contained in the prospectus that are not
historical facts. When used in this prospectus, the words "expects,"
"anticipates," "intends," "plans," "believes," "seeks," "estimates" and similar
expressions are generally intended to identify forward-looking statements.
Because these forward-looking statements involve risks and uncertainties, there
are important factors that could cause actual results to differ materially from
those expressed or implied by these forward-looking statements, including our
plans, objectives, expectations and intentions and other factors discussed under
"Risk Factors."

                                       13
<PAGE>
                                USE OF PROCEEDS

    We expect to receive approximately $32,662,500 of net proceeds from the sale
of 500,000 shares of common stock, assuming a public offering price of $69.50
per share after deducting underwriting commissions and discounts of $1,737,500
and estimated expenses of $350,000. We will not receive any proceeds from the
sale of common stock by the selling shareholders.

    We intend to use the proceeds of this offering for working capital and
general corporate purposes, including increased expenditures for sales and
marketing, research and development and professional services and technical
support. We may also use some of the proceeds for strategic acquisitions of
products and technologies that will complement or extend our existing Internet
traffic management solutions, although we are not currently planning any of
these transactions. Pending these uses, we intend to invest the net proceeds of
this offering in investment grade interest-bearing securities. We will retain
broad discretion in the allocation and use of the net proceeds of this offering.
See "Risk Factors--We may spend the offering proceeds in ways with which our
shareholders may not agree."

                                DIVIDEND POLICY

    F5 has never declared or paid any cash dividends on shares of its common
stock. We intend to retain any future earnings for future growth and do not
anticipate paying any cash dividends in the foreseeable future.

                        MARKET PRICE OF THE COMMON STOCK

    Our common stock began trading on the Nasdaq Stock Market's National Market
System on June 4, 1999 under the symbol FFIV. Prior to that time, there had been
no market for our common stock. The table below sets forth the high and low
closing sale prices for our common stock for the periods indicated:

<TABLE>
<CAPTION>
1999                                                                                               HIGH        LOW
- -----------------------------------------------------------------------------------------------  ---------  ---------
<S>                                                                                              <C>        <C>
June 4 - June 30...............................................................................  $   45.13  $   14.88
July 1 - September 8...........................................................................  $   85.00  $   27.75
</TABLE>

    The last reported sale price of our common stock on September 8, 1999 was
$69.50.

                                       14
<PAGE>
                                 CAPITALIZATION

    The following table sets forth the capitalization of F5 as of June 30, 1999
(1) on an actual basis, and (2) on a pro forma basis as adjusted to reflect, our
receipt of the estimated net proceeds from the sale of 500,000 shares of common
stock offered by us at the assumed offering price of $69.50 per share.

    The capitalization information set forth in the table below is qualified by,
and should be read in conjunction with, the more detailed financial statements
and notes of F5 appearing elsewhere in this prospectus.

<TABLE>
<CAPTION>
                                                                                              JUNE 30, 1999
                                                                                         ------------------------
                                                                                          ACTUAL     AS ADJUSTED
                                                                                         ---------  -------------
                                                                                              (IN THOUSANDS)
<S>                                                                                      <C>        <C>
Shareholders' equity:
    Common stock: no par value, 100,000,000 shares authorized, 18,108,185 issued and
      outstanding, actual; 100,000,000 shares authorized, 18,608,185 issued and
      outstanding, as adjusted         ................................................  $  45,751    $  78,414
    Note receivable from shareholder...................................................       (750)        (750)
    Unearned compensation..............................................................     (3,960)      (3,960)
    Accumulated deficit................................................................    (12,136)     (12,136)
                                                                                         ---------  -------------
        Total shareholders' equity.....................................................  $  28,905    $  61,568
                                                                                         ---------  -------------
                                                                                         ---------  -------------
</TABLE>

- ------------------------

This capitalization table excludes the following shares:

    - 2,369,262 shares subject to options outstanding as of June 30, 1999 with a
      weighted average exercise price of $1.50 per share;

    - 2,730,179 additional shares that could be issued under our stock option
      plans and stock purchase plan, and

    - 2,212,500 shares that could be issued upon exercise of warrants
      outstanding as of June 30, 1999 with a weighted average exercise price of
      $0.75 per share.

                                       15
<PAGE>
                            SELECTED FINANCIAL DATA

    The selected statement of operations data for the period February 26, 1996,
inception, to September 30, 1996, and for the years ended September 30, 1997 and
1998 and for the nine months ended June 30, 1999 and the balance sheet data at
September 30, 1997 and 1998 and June 30, 1999 are derived from the financial
statements of F5, which have been audited by PricewaterhouseCoopers LLP,
independent accountants, and included elsewhere in this prospectus. The balance
sheet data at September 30, 1996 has been derived from the financial statements
of F5 which has been audited by PricewaterhouseCoopers LLP. The financial data
for the period ended June 30, 1998 is unaudited, but has been prepared on a
basis consistent with the audited financial statements of F5 and the notes
thereto and include all adjustments (constituting only normal recurring
adjustments) which F5 considered necessary for a fair presentation of the
information. The results of operations for the nine months ended June 30, 1999
are not necessarily indicative of results to be expected for the year or for any
future periods. The data set forth below should be read in conjunction with
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" and the financial statements and the notes thereto included
elsewhere in this prospectus (in thousands, except per share data).

<TABLE>
<CAPTION>
                                                 PERIOD FROM       FISCAL YEAR ENDED       NINE MONTHS ENDED JUNE 30,
                                                FEB. 26, 1996        SEPTEMBER 30,
                                               (INCEPTION) TO     --------------------  --------------------------------
                                               SEPT. 30, 1996       1997       1998                           1999
                                             -------------------  ---------  ---------       1998        ---------------
                                                                                        ---------------
                                                                                          (UNAUDITED)
<S>                                          <C>                  <C>        <C>        <C>              <C>
STATEMENT OF OPERATIONS DATA:
Net revenues:
  Products.................................       $       2       $     229  $   4,119     $   2,537        $  11,872
  Services.................................              --              --        770           444            2,190
                                                     ------       ---------  ---------       -------          -------
Total net revenues.........................               2             229      4,889         2,981           14,062
                                                     ------       ---------  ---------       -------          -------
Cost of net revenues:
  Products.................................               1              71      1,091           694            3,085
  Services.................................              --              --        314           171              976
                                                     ------       ---------  ---------       -------          -------
Total cost of net revenues.................               1              71      1,405           865            4,061
                                                     ------       ---------  ---------       -------          -------
  Gross profit.............................               1             158      3,484         2,116           10,001
                                                     ------       ---------  ---------       -------          -------
Operating expenses:
  Sales and marketing......................              62             565      3,881         2,439            9,113
  Research and development.................             103             569      1,810         1,059            3,810
  General and administrative...............             180             383      1,041           690            2,145
  Amortization of unearned compensation....               4              69        420           205            1,797
                                                     ------       ---------  ---------       -------          -------
    Total operating expenses...............             349           1,586      7,152         4,393           16,865
                                                     ------       ---------  ---------       -------          -------
Loss from operations.......................            (348)         (1,428)    (3,668)       (2,277)          (6,864)
Interest income (expense), net.............              18             (28)        (4)          (21)             186
                                                     ------       ---------  ---------       -------          -------
Net loss...................................       $    (330)      $  (1,456) $  (3,672)    $  (2,298)       $  (6,678)
                                                     ------       ---------  ---------       -------          -------
                                                     ------       ---------  ---------       -------          -------
Net loss per share--basic and diluted......       $   (0.06)      $   (0.24) $   (0.60)    $   (0.37)       $   (0.88)
                                                     ------       ---------  ---------       -------          -------
                                                     ------       ---------  ---------       -------          -------
Weighted average shares--basic and
  diluted..................................           5,932           6,000      6,086         6,135            7,582
                                                     ------       ---------  ---------       -------          -------
                                                     ------       ---------  ---------       -------          -------
Pro forma net loss per share (unaudited):
  Net loss per share--basic and diluted....                                  $   (0.26)                     $   (0.45)
                                                                             ---------                        -------
                                                                             ---------                        -------
  Weighted average shares--basic and
    diluted................................                                     14,201                         14,923
                                                                             ---------                        -------
                                                                             ---------                        -------
</TABLE>

<TABLE>
<CAPTION>
                                                                        SEPTEMBER 30,              JUNE 30,
                                                             -----------------------------------  -----------
                                                                1996         1997        1998        1999
                                                                 ---          ---      ---------  -----------
<S>                                                          <C>          <C>          <C>        <C>
BALANCE SHEET DATA:
Cash and cash equivalents..................................   $     624    $     143   $   6,206   $  26,948
Working capital (deficit)..................................         617         (317)      6,763      26,774
Total assets...............................................         817          919       9,432      36,486
Long-term obligations......................................          29          216          --          --
Redeemable convertible preferred stock.....................          --           --       7,688          --
Shareholders' equity (deficit).............................         737         (231)        (80)     28,905
</TABLE>

                                       16
<PAGE>
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS

    THE FOLLOWING MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION
AND RESULTS OF OPERATIONS SHOULD BE READ IN CONJUNCTION WITH OUR FINANCIAL
STATEMENTS AND NOTES. OUR DISCUSSION CONTAINS FORWARD-LOOKING STATEMENTS BASED
UPON CURRENT EXPECTATIONS THAT INVOLVE RISKS AND UNCERTAINTIES, SUCH AS OUR
PLANS, OBJECTIVES, EXPECTATIONS AND INTENTIONS. OUR ACTUAL RESULTS AND THE
TIMING OF CERTAIN EVENTS COULD DIFFER MATERIALLY FROM THOSE ANTICIPATED IN THESE
FORWARD-LOOKING STATEMENTS AS A RESULT OF CERTAIN FACTORS, INCLUDING THOSE SET
FORTH UNDER "RISK FACTORS," "BUSINESS" AND ELSEWHERE IN THIS PROSPECTUS.

OVERVIEW

    F5 is a leading provider of integrated Internet traffic management solutions
designed to improve the availability and performance of mission-critical
Internet-based servers and applications. We were incorporated on February 26,
1996 and began operations in April 1996. During the period from February 26,
1996 through September 30, 1996, we were a development stage enterprise and had
no product revenues. Our operating activities during this period related
primarily to developing our initial product, recruiting personnel, building our
corporate infrastructure and raising capital.

    In July 1997, we released our first version of our
BIG/ip-Registered Trademark- Controller, and began to expand our operations. We
increased our investments in research and development, marketing programs,
domestic and international sales channels, customer support and services and our
general and administrative infrastructure. Since June 30, 1997, we have:

    - hired more than 150 employees;

    - hired sales representatives in eight domestic locations;

    - hired professional services and customer support personnel in eight
      domestic locations;

    - released several upgrades to BIG/ip;

    - released two new products, our 3DNS-Registered Trademark- Controller and
      our see/IT-TM- Network Manager;

    - engaged sales representatives in the European and Asia Pacific markets;
      and

    - established a distributor relationship with one international reseller.

    Our net revenues grew from $229,000 for the year ended September 30, 1997 to
$4.9 million for the year ended September 30, 1998, and were $14.1 million for
the nine months ended June 30, 1999. Currently, we derive approximately 73% of
our revenues from sales of BIG/ip. One of our resellers, Exodus Communications,
accounted for 21.7% of our net revenues for the nine months ended June 30, 1999
and 29.4% of our accounts receivable balance at June 30, 1999. In addition, we
expect to derive a significant portion of our net revenues from sales of BIG/ip
in the future.

    Net revenues derived from customers located outside of the United States
were $15,000 in 1997, $172,000 in 1998 and $1.0 million for the nine months
ended June 30, 1999. We plan to expand our international operations
significantly, particularly in selected countries in the European and Asia
Pacific markets, because we believe international markets represent a
significant growth opportunity. The expansion of our international operations
will be subject to a variety of risks that could significantly harm our business
and results of operations.

    Customers who purchase BIG/ip or 3DNS receive installation services and an
initial customer support contract, typically covering a 12-month period.
Customers may also purchase consulting services and renew their initial customer
support contract. As of June 30, 1999, approximately 80% of our customers have
renewed their initial customer support contract. Based on our limited operating
history, it is difficult to predict what our rate of renewals will be in the
future. We generally combine the software license,

                                       17
<PAGE>
installation, and customer support elements of our products into a package with
a single price. We allocate a portion of the sales price to each element of the
bundled package based on their respective fair values when the individual
elements are sold separately. Revenues from the license of software are
recognized when the product has been shipped and the customer is obligated to
pay for the product. Installation revenue is recognized when the product has
been installed at the customer's site. Revenues for customer support are
recognized on a straight-line basis over the service contract term. Consulting
services are customarily billed at fixed rates, plus out-of-pocket expenses. Our
ordinary payment terms to our customers are net 30 days, but we have extended
payment terms beyond net 30 days to some customers. Estimated sales returns are
based on historical experience by product and are recorded at the time revenues
are recognized.

    We have incurred losses since our inception, and as of June 30, 1999, had an
accumulated deficit of $12.1 million. Our success in growing net revenues
depends on increasing our customer base and expanding our product line as well
as continued growth of the emerging Internet traffic management market.
Accordingly, we intend to continue to invest heavily in sales and marketing,
promotion of the F5 brand, customer service and support, research and
development, operating infrastructure and general and administrative staff to
support our growth. As a result of these investments, we expect that our
operating expenses will increase significantly and that we will continue to
incur substantial operating losses for the foreseeable future. To achieve and
maintain profitability we will need to increase our net revenues significantly.
Although we have experienced rapid growth in net revenues in recent periods, we
may not be able to sustain these growth rates or achieve or sustain
profitability.

    We have recorded a total of $6.2 million of unearned compensation costs
since our inception through June 30, 1999. These charges represent the
difference between the exercise price and the deemed fair value of certain stock
options granted to our employees and outside directors. These options generally
vest ratably over a four-year period. We are amortizing these costs over the
vesting period of the options and have recorded unearned compensation charges of
$69,000 and $420,000 for the years ended September 30, 1997 and 1998,
respectively, and $205,000 and $1.8 million for the nine months ended June 30,
1998 and 1999, respectively.

    We expect to recognize amortization expense related to unearned compensation
of approximately $700,000 in the quarter ended September 30, 1999, $1.8 million,
$961,000 and $408,000 during the years ended September 30, 2000, 2001 and 2002,
respectively. We cannot guarantee, however, that we will not accrue additional
unearned compensation costs in the future or that our current estimate of these
costs will prove accurate, either of which events could seriously harm our
business and results of operations.

    In view of the rapidly changing nature of our business and our limited
operating history, we believe that period-to-period comparisons of net revenues
and operating results are not necessarily meaningful and should not be relied
upon as indications of future performance. This is particularly true of
companies such as ours that operate in new and rapidly evolving markets.

RESULTS OF OPERATIONS

    The following table sets forth certain financial data as a percentage of
total net revenues for the periods indicated. Data for the period from
inception, February 26, 1996, to September 30, 1996, are not presented because
we did not have product revenues during that period. Further, we believe amounts
from February 26, 1996 through September 30, 1996 are not comparable to the year
ended September 30, 1997

                                       18
<PAGE>
due to different lengths of the respective periods and the rapid acceleration of
our activities and related expenses throughout the 1997 period.
<TABLE>
<CAPTION>
                                                                                  YEAR ENDED          NINE MONTHS ENDED
                                                                                SEPTEMBER 30,              JUNE 30,
                                                                             --------------------  ------------------------
<S>                                                                          <C>        <C>        <C>            <C>
                                                                               1997       1998         1998         1999
                                                                             ---------  ---------  -------------  ---------

<CAPTION>
                                                                                                    (UNAUDITED)
<S>                                                                          <C>        <C>        <C>            <C>
STATEMENT OF OPERATIONS DATA:
Net revenues:
  Products.................................................................      100.0%      84.3%        85.1%        84.4%
  Services.................................................................         --       15.7         14.9         15.6
                                                                             ---------  ---------        -----    ---------
    Total net revenues.....................................................      100.0      100.0        100.0        100.0

Cost of net revenues:
  Products.................................................................       31.0       22.3         23.3         21.9
  Services.................................................................         --        6.4          5.7          7.0
                                                                             ---------  ---------        -----    ---------
    Total cost of net revenues.............................................       31.0       28.7         29.0         28.9
                                                                             ---------  ---------        -----    ---------

    Gross margin...........................................................       69.0       71.3         71.0         71.1

Operating expenses:
  Sales and marketing......................................................      246.8       79.4         81.8         64.8
  Research and development.................................................      248.5       37.0         35.5         27.1
  General and administrative...............................................      167.2       21.3         23.1         15.3
  Amortization of unearned compensation....................................       30.1        8.6          6.9         12.8
                                                                             ---------  ---------        -----    ---------
    Total operating expenses...............................................      692.6      146.3        147.3        120.0
                                                                             ---------  ---------        -----    ---------
Loss from operations.......................................................     (623.6)     (75.0)       (76.3)       (48.9)
Interest income (expense), net.............................................      (12.2)      (0.1)        (0.7)         1.3
                                                                             ---------  ---------        -----    ---------
Net loss...................................................................     (635.8)%     (75.1)%       (77.0)%     (47.6)%
                                                                             ---------  ---------        -----    ---------
                                                                             ---------  ---------        -----    ---------
</TABLE>

NINE MONTHS ENDED JUNE 30, 1998 (UNAUDITED) AND 1999

    Net Revenues:

    Net revenues consist of sales of our products and services, which include
software licenses and services. Services include revenue from service and
support agreements provided as part of the initial product sale, sales of
extended service and support contracts and consulting services.

    PRODUCT REVENUES.  Product revenues increased by 368.0% from $2.5 million
for the nine months ended June 30, 1998 to $11.9 million for the nine months
ended June 30, 1999. This increase in product revenues was due primarily to an
increase in the quantity of our products sold through our sales direct and
indirect channels including the sales of our new products.

    SERVICE REVENUES.  Service revenues increased by 393.2% from $444,000 for
the nine months ended June 30, 1998 to $2.2 million for the nine months ended
June 30, 1999. This increase was due primarily to an increase in the installed
base of our products which resulted in increased revenues from service and
support contracts.

    As our net revenue base increases, we do not believe we can sustain
percentage growth rates of net revenues that we have experienced historically.

                                       19
<PAGE>
    Cost of Net Revenues:

    Cost of net revenues consists primarily of out-sourced hardware components
and manufacturing, fees for third-party software products integrated into our
products, service and support personnel and an allocation of our facilities and
depreciation expenses.

    COST OF PRODUCT REVENUES.  Cost of product revenues increased 344.5%, from
$694,000 for the nine months ended June 30, 1998 to $3.1 million for the nine
months ended June 30, 1999. Cost of product revenues decreased as a percent of
product revenues from 27.4% for the nine months ended June 30, 1998, to 26.0%
for the nine months ended June 30, 1999. The increase in absolute dollars was
due primarily to an increase in product revenues. The decrease in cost of
product revenues as a percentage of product revenues was the result of higher
utilization of manufacturing operations, including increased economies of scale
achieved from an increase in production.

    COST OF SERVICE REVENUES.  Cost of service revenues increased 470.8%, from
$171,000 for the nine months ended June 30, 1998 to $976,000 for the nine months
ended June 30, 1999. Cost of service revenues increased as a percent of service
revenues from 38.5% for the nine months ended June 30, 1998 to 44.6% for the
nine months ended June 30, 1999. The increases in cost of service revenues in
absolute dollars and as a percent of service revenues was due primarily to
increases in service and support personnel.

    SALES AND MARKETING.  Our sales and marketing expenses consist primarily of
salaries, commissions and related benefits of our sales and marketing staff,
costs of our marketing programs, including public relations, advertising and
trade shows and an allocation of our facilities and depreciation expenses. Sales
and marketing expenses increased by 273.6%, from $2.4 million for the nine
months ended June 30, 1998 to $9.1 million for the nine months ended June 30,
1999. This increase was due to an increase in sales and marketing personnel and
professional services personnel from 17 to 67, and increased advertising and
promotional activities. We expect to increase sales and marketing expenses in
order to grow net revenues and expand our brand awareness.

    RESEARCH AND DEVELOPMENT.  Our research and development expenses consist
primarily of salaries and related benefits for our product development personnel
and an allocation of our facilities and depreciation expenses. Research and
development expenses increased by 259.8%, from $1.1 million for the nine months
ended June 30, 1998 to $3.8 million for the nine months ended June 30, 1999.
This increase was due to an increase in product development personnel from 21 to
54. Our future success is dependent in large part on the continued enhancement
of our current products and our ability to develop new, technologically advanced
products that meet the sophisticated needs of our customers. We expect research
and development expenses to increase in future periods.

    GENERAL AND ADMINISTRATIVE.  Our general and administrative expenses consist
primarily of salaries, benefits and related costs of our executive, finance,
human resource and legal personnel, third-party professional service fees, and
an allocation of our facilities and depreciation expenses. General and
administrative expenses increased by 210.9% from $690,000 for the nine months
ended June 30, 1998 to $2.1 million for the nine months ended June 30, 1999.
This increase was due primarily to an increase in general and administrative
personnel from 20 to 30. We expect general and administrative expenses to
increase as we expand our staff, further develop our internal information
systems and incur costs associated with being a publicly held company.

    UNEARNED COMPENSATION.  We recorded unearned compensation charges of
$205,000 and $1.8 million for the nine months ended June 30, 1998 and 1999,
respectively. See Note 8 of notes to our financial statements.

    INTEREST INCOME (EXPENSE) NET.  Interest income consists of earnings on our
cash and cash equivalent balances offset by interest expense associated with
debt obligations. Net interest expense was $21,000 for

                                       20
<PAGE>
the nine months ended June 30, 1998 compared to net interest income of $186,000
for the nine months ended June 30, 1999. This increase was due primarily to the
investment of the proceeds received from the initial public offering in June
1999.

    INCOME TAXES.  There was no provision for federal or state income taxes for
any period as we have incurred operating losses since inception. As of June 30,
1999, we had approximately $8.8 million of net operating loss carryforwards for
federal income tax purposes. Utilization of the net operating loss carryforwards
may be subject to annual limitations due to the ownership change limitations
contained in the Internal Revenue Code of 1986 and similar state provisions.
Annual limitations may result in the expiration of the net operating losses
before we can utilize them. The federal net operating loss carryforwards will
expire at various dates beginning in 2011 through 2018 if we do not use them.
See Note 5 of notes to our financial statements.

YEARS ENDED SEPTEMBER 30, 1997 AND 1998

    Net Revenues:

    PRODUCT REVENUES.  Product revenues increased by 1,698.7% from $229,000 in
1997 to $4.1 million in 1998. This increase was due primarily to an increase in
the quantity of our products sold.

    SERVICE REVENUES.  There were no service revenues in 1997 because the
initial product sales during that period did not include a service and support
contract. Beginning in fiscal year 1998, our products included a service and
support contract. Service revenues were $770,000 in 1998. This increase in
service revenues was due to an increase in the installed base of our products
which included a service and support contract.

    Cost of Net Revenues:

    COST OF PRODUCT REVENUES.  Cost of product revenues increased by 1,436.6%
from $71,000 in 1997 to $1.1 million in 1998. This increase was due primarily to
the increase in our products sold. Cost of product revenues as a percentage of
net revenues decreased from 31.0% to 26.5% due to a decrease in direct product
costs including costs of manufacturing personnel as a percentage of revenue.

    COST OF SERVICE REVENUES.  Cost of service revenues was $314,000 in 1998.
Cost of service revenues as a percent of service revenues was 40.8% in 1998. We
expect that the cost of service revenues will fluctuate in the future based on
the rate of increase in service and support personnel compared with increases in
service revenues.

    SALES AND MARKETING.  Our sales and marketing expenses increased by 586.9%,
from $565,000 in 1997 to $3.9 million in 1998. This increase was due primarily
to investing in our sales and marketing infrastructure, both domestically and
internationally. These investments included an increase in our sales and
marketing and professional services personnel from 7 to 37, recruiting fees,
travel expenses, and increased marketing activities, including advertising,
trade shows and other promotional expenses. Sales and marketing expenses
decreased from 246.8% of net revenues in 1997 to 79.4% of net revenues in 1998.
This percentage decrease was due primarily to our net revenues growing faster
than our sales and marketing expenses.

    RESEARCH AND DEVELOPMENT.  Our research and development expenses increased
by 218.1% from $569,000 in 1997 to $1.8 million in 1998. This increase was due
primarily to an increase in our software engineers and other technical staff
from 9 to 27. Research and development expenses decreased from 248.5% of our net
revenues in 1997 to 37.0% of our net revenues in 1998. This percentage decrease
was due primarily to our net revenues growing faster than our research and
development expenses.

                                       21
<PAGE>
    GENERAL AND ADMINISTRATIVE.  Our general and administrative expenses
increased by 171.8% from $383,000 in 1997 to $1.0 million in 1998. This increase
was due primarily to an increase in general and administrative personnel from 4
to 16. General and administrative costs decreased from 167.2% of our net
revenues in 1997 to 21.3% of our net revenues in 1998. This percentage decrease
was due primarily to our net revenues growing faster than our general and
administrative expenses.

    INTEREST INCOME (EXPENSE), NET.  Net interest expense was $28,000 in 1997
compared to net interest expense of $4,000 in 1998. This decrease was due
primarily to increased interest earned on cash and cash equivalents received
from the sale of our preferred stock in August 1998.

QUARTERLY RESULTS OF OPERATIONS

    The following tables present our unaudited quarterly results of operations
for the seven quarters ended June 30, 1999 in dollars and as a percentage of net
revenues. You should read the following tables in conjunction with our financial
statements and related notes in this prospectus. We have prepared this unaudited
information on the same basis as the audited financial statements. These tables
include all adjustments, consisting only of normal recurring adjustments that we
consider necessary for a fair presentation of our operating results for the
quarters presented. You should not draw any conclusions about our future results
from the results of operations for any quarter.

<TABLE>
<CAPTION>
                                                                             THREE MONTHS ENDED
                                          -----------------------------------------------------------------------------------------
                                            DEC. 31,     MARCH 31,   JUNE 30,     SEPT. 30,       DEC. 31,     MARCH 31,   JUNE 30,
                                              1997         1998        1998         1998            1998         1999        1999
                                          ------------   ---------   --------   -------------   ------------   ---------   --------
                                                                               (IN THOUSANDS)
                                                                                 (UNAUDITED)
<S>                                       <C>            <C>         <C>        <C>             <C>            <C>         <C>
Net revenues:
  Products..............................     $ 742        $  866     $   929       $ 1,582        $ 2,282       $3,146     $ 6,444
  Services..............................       100           129         215           326            413          616       1,161
                                             -----       ---------   --------   -------------   ------------   ---------   --------
    Total net revenues..................       842           995       1,144         1,908          2,695        3,762       7,605

Cost of net revenues:
  Products..............................       201           202         291           397            624          825       1,636
  Services..............................         9            47         115           143            196          384         396
                                             -----       ---------   --------   -------------   ------------   ---------   --------
    Total cost of net revenues..........       210           249         406           540            820        1,209       2,032
                                             -----       ---------   --------   -------------   ------------   ---------   --------

    Gross profit........................       632           746         738         1,368          1,875        2,553       5,573
                                             -----       ---------   --------   -------------   ------------   ---------   --------

Operating expenses:
  Sales and marketing...................       555           787       1,097         1,442          2,216        2,887       4,010
  Research and development..............       194           340         525           751          1,020        1,324       1,466
  General and administrative............       202           236         252           351            525          666         954
  Amortization of unearned
    compensation........................        31            60         114           215            368          670         759
                                             -----       ---------   --------   -------------   ------------   ---------   --------
    Total operating expenses............       982         1,423       1,988         2,759          4,129        5,547       7,189
                                             -----       ---------   --------   -------------   ------------   ---------   --------
Loss from operations....................      (350)         (677)     (1,250)       (1,391)        (2,254)      (2,994)     (1,616)
Interest income (expense), net..........       (23)            4          (2)           17             58           31          97
                                             -----       ---------   --------   -------------   ------------   ---------   --------
Net loss................................     $(373)       $ (673)    $(1,252)      $(1,374)       $(2,196)      $(2,963)   $(1,519)
                                             -----       ---------   --------   -------------   ------------   ---------   --------
                                             -----       ---------   --------   -------------   ------------   ---------   --------
</TABLE>

                                       22
<PAGE>

<TABLE>
<CAPTION>
                                                                             THREE MONTHS ENDED
                                          -----------------------------------------------------------------------------------------
                                            DEC. 31,     MARCH 31,   JUNE 30,     SEPT. 30,       DEC. 31,     MARCH 31,   JUNE 30,
                                              1997         1998        1998         1998            1998         1999        1999
                                          ------------   ---------   --------   -------------   ------------   ---------   --------
                                                                                 (UNAUDITED)
<S>                                       <C>            <C>         <C>        <C>             <C>            <C>         <C>
Net revenues:
  Products..............................      88.1%         87.0%       81.2%        82.9%          84.7%         83.6%       84.7%
  Services..............................      11.9          13.0        18.8         17.1           15.3          16.4        15.3
                                             -----       ---------   --------       -----          -----       ---------   --------
    Total net revenues..................     100.0         100.0       100.0        100.0          100.0         100.0       100.0

Cost of net revenues:
  Products..............................      23.9          20.3        25.4         20.8           23.1          21.9        21.5
  Services..............................       1.0           4.7        10.1          7.5            7.3          10.2         5.2
                                             -----       ---------   --------       -----          -----       ---------   --------
    Total cost of net revenues..........      24.9          25.0        35.5         28.3           30.4          32.1        26.7
                                             -----       ---------   --------       -----          -----       ---------   --------

    Gross margin........................      75.1          75.0        64.5         71.7           69.6          67.9        73.3
                                             -----       ---------   --------       -----          -----       ---------   --------

Operating expenses:
  Sales and marketing...................      65.9          79.1        95.9         75.5           82.2          76.7        52.7
  Research and development..............      23.0          34.2        45.9         39.4           37.8          35.2        19.3
  General and administrative............      24.0          23.7        22.0         18.4           19.5          17.8        12.5
  Amortization of unearned
    compensation........................       3.7           6.0        10.0         11.3           13.7          17.8        10.0
                                             -----       ---------   --------       -----          -----       ---------   --------
    Total operating expenses............     116.6         143.0       173.8        144.6          153.2         147.5        94.5
                                             -----       ---------   --------       -----          -----       ---------   --------
Loss from operations....................     (41.5)        (68.0)     (109.3)       (72.9)         (83.6)        (79.6)      (21.2)
Interest income (expense), net..........      (2.8)          0.4        (0.1)         0.9            2.1           0.8         1.3
                                             -----       ---------   --------       -----          -----       ---------   --------
Net loss................................     (44.3)%       (67.6)%    (109.4)%      (72.0)%        (81.5)%       (78.8)%     (19.9)%
                                             -----       ---------   --------       -----          -----       ---------   --------
                                             -----       ---------   --------       -----          -----       ---------   --------
</TABLE>

    Our quarterly operating results have fluctuated significantly and we expect
that future operating results will be subject to similar fluctuations for a
variety of factors, many of which are substantially outside our control. See
"Risk Factors--Our quarterly operating results are volatile and future operating
results remain uncertain."

LIQUIDITY AND CAPITAL RESOURCES

    From our inception through May 1999, we financed our operations and capital
expenditures primarily through the sale of approximately $12.4 million in equity
securities. In June 1999 we completed an initial public offering of 2,860,000
shares of common stock and raised approximately $25 million, net of offering
costs.

    As of June 30, 1999, we had a $2.0 million working capital line of credit
with a lender. At June 30, 1999, there were no borrowings outstanding under this
line of credit. This line of credit was not renewed when it expired on August
31, 1999.

    Cash used in our operating activities was $1.7 million for the nine months
ended June 30, 1998, and $3.9 million for the nine months ended June 30, 1999.
These net cash outflows resulted from operating losses as well as increases in
accounts receivable due to increased sales and other current assets and were
partially offset by increases in accounts payable, accrued liabilities and
deferred revenues. The Company anticipates that in the future it will offer
financing to certain resellers. To the extent such financing is offered cash
used in operating activities will increase to fund the increase in outstanding
accounts receivables.

    Cash used in investing activities was $580,000 for the nine months ended
June 30, 1998 and $1.5 million for the nine months ended June 30, 1999,
substantially all of which was used for the purchase

                                       23
<PAGE>
of property and equipment. We expect capital expenditures to continue to
increase through the end of 1999, due to the costs of expansion and expenditures
for information systems and test equipment.

    As of June 30, 1999, our principal commitment consisted of obligations
outstanding under operating leases. In March 1999 we agreed to lease
approximately 20,000 square feet in a facility located in Seattle, Washington
for a term of 60 months. In July 1999, we agreed to lease an additional 8,000
square feet in a facility located in Seattle, Washington, for a term of 84
months. The annual cost of these leases is approximately $561,000, subject to
annual adjustments. We have also signed a lease for approximately 84,000 square
feet of new office space in Seattle, Washington in a building which is currently
under construction. This lease will commence on approximately July 1, 2000 with
a term of 12 years. The annual cost of this lease is approximately $2,000,000,
subject to annual adjustments plus expenses. Our obligation under the lease is
collateralized by a secured letter of credit in the amount of $2.5 million.
Although we have no other material commitments, we anticipate a substantial
increase in our capital expenditures and lease commitments consistent with
anticipated growth in our operations, infrastructure and personnel. In the
future we may also require a larger inventory of products in order to provide
better availability to customers and achieve purchasing efficiencies. We expect
that the net proceeds from this offering, our existing cash balances and cash
from operations will be sufficient to meet our currently anticipated working
capital and capital expenditures for the foreseeable future.

MARKET RISK DISCLOSURES

    We do not hold derivative financial instruments or equity securities in our
investment portfolio. Our cash equivalents consist of high-quality securities,
as specified in our investment policy guidelines. The policy limits the amount
of credit exposure to any one issue or issuer to a maximum of 20% of the total
portfolio with the exception of treasury securities, commercial paper, and money
market funds, which are exempt from size limitation. The policy limits all
short-term investments to mature in two years or less, with the average maturity
being one year or less. These securities are subject to interest rate risk and
will decrease in value if interest rates increase.

RECENT ACCOUNTING PRONOUNCEMENTS

    As of October 1, 1998 we adopted Financial Accounting Standards Board
Statement No. 130, "Reporting Comprehensive Income," which establishes standards
for reporting and displaying comprehensive income and its components in a full
set of general-purpose financial statements. We had no material components of
comprehensive income. The adoption of this statement has had no impact on our
financial position, shareholders' equity (deficit), results of operations or
cash flows. Accordingly, our comprehensive loss for the nine months ended June
30, 1999 is equal to our reported loss.

    Additionally, the Financial Accounting Standards Board issued Statement No.
131, "Disclosures about Segments of an Enterprise and Related Information,"
which establishes standards for the way business enterprises report information
in annual statements and interim financial reports regarding operating segments,
products and services, geographic areas and major customers. This statement is
effective for financial statements for fiscal years beginning after December 15,
1997. The adoption of this statement did not have a material impact on the way
we report information in our financial statements.

    In March 1998, the American Institute of Certified Public Accountants issued
Statement of Position 98-1 ("SOP 98-1"), "Accounting for the Costs of Computer
Software Developed or Obtained for Internal Use," which establishes guidelines
for the accounting for the costs of all computer software developed or obtained
for internal use. We are required to adopt SOP 98-1 for the fiscal year
beginning in October 1999. Our adoption of SOP 98-1 is not expected to have a
material impact on our financial statements.

    In June 1998, the Financial Accounting Standards Board issued Statement No.
133 of Financial Accounting Standards, "Accounting for Derivative Instruments
and Hedging Activities." This statement requires that all derivative instruments
be recorded on the balance sheet at their fair value. Changes in the

                                       24
<PAGE>
fair value of derivatives are recorded each period in current earnings or other
comprehensive income, depending on whether a derivative is designated as a part
of a hedge transaction and, if it is, the type of hedge transaction. In July
1999, the FASB issued SFAS No. 137, "Accounting for Derivative Instruments and
Hedging Activities--Deferral of the Effective Date of FASB Statement No. 133."
SFAS No. 137 deferred the effective date of SFAS No. 133 until fiscal years
beginning after June 15, 2000. We do not use derivative instruments, therefore
the adoption of this statement will not have any effect on our results of
operations or financial position.

YEAR 2000 COMPLIANCE

    BACKGROUND OF YEAR 2000 ISSUES.  Many currently installed computer and
communications systems and software products are unable to distinguish 21(st)
century dates from 20(th) century dates. This situation could result in system
failures or miscalculations causing business disruptions. As a result, many
companies' software and computer and communications systems may need to be
upgraded or replaced to become Year 2000 compliant.

    OUR PRODUCT TESTING AND LICENSING.  We have tested all of our current
products for Year 2000 compliance. We derived our testing method from our review
and analysis of the Year 2000 testing practices of other software vendors,
relevant industry Year 2000 compliance standards and the specific functionality
and operating environments of our products. The tests are run on all supported
platforms for each current release of our product and include testing for date
calculations and internal storage of date information with test numbers starting
in 1999 and going beyond the Year 2000. Based on these tests, we believe our
products to be Year 2000 compliant with respect to date calculations and
internal storage of date information.

    CUSTOMER CLAIMS.  We may be subject to customer claims to the extent our
products fail to operate properly as a result of the occurrence of the date
January 1, 2000. Liability may result to the extent our products are not able to
store, display, calculate, compute and otherwise process date-related data. We
could also be subject to claims based on the failure of our products to work
with software or hardware from other vendors.

    OUR EXTERNAL VENDORS.  We periodically verify Year 2000 compliance by
external vendors that supply us with material software and information systems
and communicate with our significant suppliers to determine their Year 2000
readiness. As part of our assessment, we periodically evaluate the level of
validation we require of third parties to ensure their Year 2000 readiness. To
date, we have not encountered any material Year 2000 problems with software and
information systems provided to us by third parties.

    OUR INTERNAL SYSTEMS.  We periodically review our internal management
information and other systems to identify any products, services or systems that
may not be Year 2000 compliant and to take corrective action when required. To
date, we have not encountered any material Year 2000 problems with our computer
systems or any other equipment that might be subject to such problems.

    COSTS OF ADDRESSING YEAR 2000 COMPLIANCE.  Based on our preliminary
evaluations, we do not believe we will incur significant expenses or be required
to invest heavily in computer system improvements to be Year 2000 compliant. We
do not believe the cost of remediation for Year 2000 non-compliance issues
identified to date will exceed $50,000. However, significant uncertainty exists
concerning the potential costs and effects associated with Year 2000 compliance.
Any Year 2000 compliance problem experienced by us or our customers could
decrease demand for our products which could seriously harm our business and
results of operations.

    CONTINGENCY PLANNING.  We are formulating a contingency plan at this time
and expect to have specific contingency plans in place prior to November 30,
1999.

                                       25
<PAGE>
                                    BUSINESS

    THE FOLLOWING BUSINESS SECTION CONTAINS FORWARD-LOOKING STATEMENTS RELATING
TO FUTURE EVENTS OR THE FUTURE FINANCIAL PERFORMANCE OF F5, WHICH INVOLVE RISKS
AND UNCERTAINTIES. OUR ACTUAL RESULTS COULD DIFFER MATERIALLY FROM THOSE
ANTICIPATED IN THESE FORWARD-LOOKING STATEMENTS AS A RESULT OF CERTAIN FACTORS,
INCLUDING THOSE SET FORTH UNDER "RISK FACTORS" AND ELSEWHERE IN THIS PROSPECTUS.

OVERVIEW

    F5 is a leading provider of integrated Internet traffic management solutions
designed to improve the availability and performance of mission-critical
Internet-based servers and applications. Our products monitor and manage local
and geographically dispersed servers and intelligently direct traffic to the
server best able to handle a user's request. Our products are designed to help
prevent system failure and provide timely responses to user requests and data
flow. Our BIG/ip-Registered Trademark- and 3DNS-Registered Trademark-
Controllers, when combined with our see/IT-TM- Network Manager, help
organizations optimize their network server availability and performance and
cost-effectively manage their Internet infrastructure. Our solutions are used by
organizations who rely on the Internet as a fundamental component of their
business. Our customers include Internet service providers, such as Exodus
Communications, Frontier GlobalCenter, PSINet, and MCI WorldCom, e-commerce
companies and many other organizations that employ high-traffic Internet sites.
We have sold our products to over 600 end-customers as of August 31, 1999.

INDUSTRY BACKGROUND

    The Internet has emerged as a critical commerce and communications platform
for businesses and consumers worldwide. International Data Corporation estimates
that there were approximately 100 million Internet users at the end of 1998 and
anticipates this number will grow to approximately 320 million by 2002. This
dramatic growth in the number of Internet users coupled with the increased
availability of powerful new tools and equipment that enable the development,
processing and distribution of data across the Internet have led to a
proliferation of Internet-based applications and services, such as e-commerce,
e-mail, electronic file transfers and online interactive applications. At the
same time that the number of users of, and uses for, the Internet has increased
significantly, the complexity and volume of Internet traffic has increased
dramatically. According to UUNet, Internet traffic doubles every 100 days.

    As a result of the Internet's growing popularity and capabilities, numerous
businesses have come to rely on it as a fundamental commerce and communications
tool. For example, a growing number of organizations, such as Web hosting and
e-commerce companies, rely primarily on the Internet to transact business. In
addition, many businesses are using the Internet to deploy mission-critical
business applications in browser-based intranet and extranet computing
environments. Failure to deliver the expected availability and performance for
these Internet-based applications can result in a significant cost to the
organization.

    This widespread proliferation in the use and importance of the Internet has
strained many organizations' network infrastructures. In order to support the
dramatic increases in Internet use and traffic, many organizations have
aggressively expanded network server capacity. According to IBM, servers are
being connected to the Internet at a rate of 53,000 per month. Network
infrastructures are further strained by unpredictable traffic, the complexity of
the network environment and the increased variety of data, including multimedia
components and video clips. In this environment, organizations often deploy
multiple servers in a group, or array, which contains individual
application-specific servers or redundant servers that operate together as a
virtual large server. Server arrays can reduce single points of failure and be a
cost-effective way to increase the potential capacity of the system by providing
the flexibility to add additional servers to the array as needed. The practice
of geographically dispersing server arrays to help prevent system failure and
direct traffic more efficiently is also a growing trend.

                                       26
<PAGE>
    While additional servers, redundant server configurations and geographically
dispersed server sites help address an organization's rapidly increasing
traffic, they also increase the organization's need for sophisticated Internet
traffic management tools to help manage the availability and performance of its
servers and applications. For optimal server array performance, intelligent
devices are required to direct traffic and synchronize content across local and
geographically dispersed servers. These intelligent devices, or load balancers,
identify which server, whether local or remote, is best able to handle user
requests.

    Most currently available Internet traffic management products are extensions
to hardware-based routers, which lack the robust functionality required to
support current mission-critical Internet-based servers and applications. These
products are typically not designed to address application availability, nor do
they meet the manageability and scalability required by organizations who depend
on the Internet as a fundamental commerce and communications tool. As a result,
we believe that traditional traffic management products do not adequately
address the need to manage traffic flows and ensure the availability of
mission-critical servers and applications in the rapidly changing Internet
environment.

F5 SOLUTION

    We develop, market and support cost-effective, integrated Internet traffic
management solutions designed to ensure that mission-critical Internet-based
servers and applications are continuously available and perform reliably. Our
products monitor and manage locally and geographically dispersed servers and
intelligently direct traffic to the server best able to handle the user request.
We believe that our products deliver Internet quality control by providing the
following key benefits:

    HIGH SYSTEM AVAILABILITY.  Our integrated suite of products works with
servers deployed in a redundant server array over a local or wide area network
to enhance network performance and reduce single points of failure. Our
solutions continuously monitor network performance to enable real-time detection
of server, application and content degradation or failure. Based on this
information, our solutions automatically direct user requests to functioning
servers and applications. Our products also enable network administrators to
deploy new servers and take individual servers offline for routine maintenance
without disrupting service to end users.

    INCREASED PERFORMANCE.  Our products provide a significant performance
improvement over other current approaches. Our solutions monitor server and
application response time and verify content. This information is used to
intelligently direct user requests to the server with the fastest response time.
By intelligently allocating traffic throughout the network, our solutions reduce
server overload conditions that may cause performance degradation.

    COST-EFFECTIVE SCALABILITY.  Our solutions enable more efficient utilization
of existing server capacity by intelligently allocating traffic among servers.
This capability allows organizations to optimize the capacity of existing
servers and, as traffic volume dictates, cost-effectively expand server capacity
through incremental additions of relatively low cost servers rather than
upgrading to larger, more expensive servers. Our solutions can be used with
multiple heterogeneous hardware platforms, allowing organizations to protect
their investments in their legacy hardware installations as well as integrate
future hardware investments.

    EASIER NETWORK MANAGEABILITY.  Our products collect information that can be
used to facilitate network management and planning from a central location.
Leveraging our products' strategic location in the network, our solutions
collect data that is crucial for traffic analysis and apply proprietary trend
and analysis tools that synthesize this data so that network managers can
forecast network requirements more accurately. In addition, we are in the
process of developing solutions to automatically synchronize content across
remote locations, thereby helping to ensure users access to the same content
regardless of server location.

    ENHANCED NETWORK CONTROL.  Our solutions enable organizations to prioritize
and arrange network traffic based on user-defined criteria to meet their
specific needs. For example, our products may be

                                       27
<PAGE>
configured to utilize the most cost-efficient communication links or,
alternatively, to achieve the most rapid response time.

STRATEGY

    Our objective is to be the leading provider of integrated Internet traffic
management solutions designed to optimize network server availability and
performance. Key components of our strategy include:

    OFFER A COMPLETE INTERNET TRAFFIC MANAGEMENT SOLUTION.  We plan to continue
expanding our existing suite of products to provide a complete Internet traffic
management solution that further optimizes the availability and performance of
network servers and applications. To support this objective, we have recently
introduced our see/IT-TM- Network Manager that communicates with our BIG/ip and
3DNS Controllers to enable real-time network monitoring and pro-active network
management. Furthermore, we are currently developing our global/SITE-TM-
Controller that is designed to ensure data integrity by automatically
synchronizing content across local and geographically dispersed network servers.
To further support our suite of products, we intend to continue to invest in our
professional services group to provide the installation, training and support
services required to help our customers optimize their use of our Internet
traffic management solutions.

    INVEST IN TECHNOLOGY TO CONTINUE TO MEET CUSTOMER NEEDS.  We plan to
continue to invest in research and development to provide our customers with
complete Internet traffic management solutions that meet their needs. Our
current technology platform has been designed to quickly and easily expand the
features and functionalities of our suite of products as well as develop
additional products that address the complex and changing needs of our
customers. We are also in the process of developing specialized software modules
that will allow our customers to purchase products with specific features based
on their specific requirements.

    EXPAND SALES CHANNELS AND GEOGRAPHIC SCOPE OF SALES.  We plan to invest
significant resources to expand our direct sales force and further develop our
indirect sales channels. In addition to maintaining a strong direct sales force,
we plan to expand our indirect sales channels through leading industry
resellers, original equipment manufacturers, systems integrators, Internet
service providers and other channel partners. Furthermore, we plan to expand
sales of our Internet traffic management solutions to government entities. We
also plan to aggressively develop our direct and indirect international sales
capabilities, particularly in selected countries in the European and Asia
Pacific markets.

    BUILD AND EXPAND RELATIONSHIPS WITH STRATEGIC PARTNERS.  We plan to
capitalize on products, technologies and channels that may be available through
partners. We currently have an OEM relationship with Cabletron and a licensing
agreement for our BIG/ip load-balancing technology with Extreme Networks. We
continue to seek relationships with partners that will enable us to increase the
market opportunity for our products and technologies.

    LEVERAGE OUR MARKET LEADERSHIP TO CONTINUE TO BUILD THE F5 BRAND.  We plan
to continue building brand awareness that positions us as one of the leading
providers of Internet traffic management solutions. Our goal is for the F5 brand
to be synonymous with superior network performance, high quality customer
service and ease of use. To achieve these objectives, we plan to increase our
investments in a broad range of marketing programs, including active tradeshow
participation, advertising in print publications, direct marketing, high-profile
Web events and our Internet site.

    PURSUE STRATEGIC ACQUISITIONS.  We may selectively pursue strategic
acquisitions for products and technologies that will complement or expand our
existing Internet traffic management solutions.

                                       28
<PAGE>
PRODUCTS AND TECHNOLOGY

    We have developed BIG/ip, 3DNS and see/IT-TM- as a suite of Internet traffic
management products that facilitate high performance, high availability and
scalable access to network server arrays located at a single site or across
multiple, geographically dispersed sites. Our suite of products helps to ensure
that Web servers can respond to ever-increasing Internet traffic. The following
is a summary of our products currently available and under development:

<TABLE>
<CAPTION>
- -------------------------------------------------------------------------------------------

           PRODUCT NAME                          DESCRIPTION              INTRODUCTION DATE
<S>                                  <C>                                  <C>
BIG/ip-Registered Trademark-         Intelligent load balancer for local  July 1997
Controller                           area networks
3DNS-Registered Trademark-           Intelligent load balancer for wide   September 1998
Controller                           area networks
see/IT-TM- Network Manager           Traffic analysis and network         April 1999
                                     management software application for
                                     BIG/ip and 3DNS
global/SITE-TM- Controller           File replication and                 Under development
                                     synchronization controller for
                                     managing content across
                                     geographically dispersed Internet
                                     sites
</TABLE>

    BIG/IP CONTROLLER.  BIG/ip is an intelligent load balancer consisting of our
proprietary software, which we load on a pre-configured, industry-standard
hardware platform. Situated between a network's routers and server array, BIG/ip
continuously monitors the array of local servers to ensure application
availability and performance and automatically directs user requests to the
server best able to handle these requests. By quickly detecting application,
server and network failures and directing service toward those servers and
applications that are functioning properly, BIG/ip is designed to help prevent
system failure and provide timely responses to user requests and data flow.
BIG/ip offers a comprehensive choice of load-balancing algorithms that enables
an organization to choose a load-balancing configuration that best suits its
particular needs. Additionally, BIG/ip actively queries and checks content
received from applications, thereby helping to ensure the quality of Web
content. Thus, if a server and application are responding to users' requests
with incorrect content, BIG/ip redirects requests to those servers and
applications that are responding properly.

    BIG/ip is compatible with any system that uses the standard Internet
communication method, also known as Internet protocol or IP, and can operate
with multiple, heterogeneous hardware platforms. This enables organizations to
leverage their existing infrastructure without limiting their options to meet
future network needs. BIG/ip supports a wide variety of network protocols,
including Web, e-mail, audio, video, database and file transfer protocol, which
is the standard method of transfering files over the Internet. BIG/ip also
manages traffic for network devices such as firewalls that prevent unauthorized
access to a network system, cache servers that store frequently accessed Web
content and multimedia servers, to help provide reliable content availability
for end users. BIG/ip's ability to intelligently distribute traffic across
server arrays reduces the need for increasingly larger and more expensive
servers to accommodate increases in network traffic. This configuration also
reduces the single point of failure inherent with a single large server and
allows for the orderly addition of new servers or the routine maintenance or
upgrades of servers without disrupting service to the end user. A typical
configuration of redundant BIG/ip Controllers located between the server array
and network is shown below.

                                       29
<PAGE>
                             [ILLUSTRATION]

    Illustration of redundant BIG/ip Controllers sitting between an
    organization's server array and network

    Additional BIG/ip features include:

    - SECURE SOCKETS LAYER SESSION PERSISTENCE enables server arrays to support
      e-commerce and other applications in a secure, cost-effective and scalable
      environment.

    - SECURE SERVER PROTECTION protects against unauthorized use of the network
      server array.

    - RATE SHAPING allows priority levels to be assigned to specific types of
      traffic.

    - PACKET FILTERING enables content providers to direct network traffic to
      servers based on user-definable criteria for increased network security
      and performance.

    - BIG/CONFIG, a simple point-and-click browser-based installation and
      configuration tool, facilitates remote monitoring and administration of
      the network in a secure environment.

    3DNS CONTROLLER.  3DNS is an intelligent load balancer that manages and
distributes user requests across wide area networks. 3DNS consists of our
proprietary software, which we load on a pre-configured, industry-standard
hardware platform. Like BIG/ip, 3DNS functions with multiple heterogeneous
hardware platforms and supports a wide variety of network protocols, including
Web, e-mail, audio, video, database and file transfer protocol, and manages
traffic for network devices such as firewalls, cache servers and multimedia
servers.

                                       30
<PAGE>
    When an end-user request is received from a local domain name server or DNS,
3DNS collects network information and communicates with each BIG/ip in the
network to determine the server array with the fastest response time. 3DNS then
sends the request to the BIG/ip at this server array, and the BIG/ip then
directs the request to the individual server best able to handle it. Although
organizations can deploy a single 3DNS in their network configuration, multiple
3DNS Controllers are often deployed within the network to provide redundancy to
help ensure network availability and performance for end users. A typical 3DNS
configuration is shown below:

                             [ILLUSTRATION]

                                       31
<PAGE>
                                   MANAGEMENT

    THE FOLLOWING TABLE SETS FORTH CERTAIN INFORMATION WITH RESPECT TO OUR
EXECUTIVE OFFICERS AND DIRECTORS AS OF AUGUST 31, 1999:

EXECUTIVE OFFICERS AND DIRECTORS

<TABLE>
<CAPTION>
NAME                                                AGE POSITION
- --------------------------------------------------  --- --------------------------------------------------
<S>                                                 <C> <C>
Jeffrey S. Hussey.................................  38  Chairman of the Board, Chief Executive Officer and
                                                          President
Robert J. Chamberlain.............................  46  Vice President of Finance, Chief Financial Officer
                                                        and Treasurer
Steven Goldman....................................  39  Senior Vice President of Sales, Marketing and
                                                        Services
Brett L. Helsel...................................  39  Vice President of Product Development and Chief
                                                          Technology Officer
Carlton G. Amdahl (1).............................  47  Director
Karl D. Guelich (1)(2)............................  57  Director
Alan J. Higginson (2).............................  52  Director
Sonja L. Hoel (2).................................  33  Director
Kent L. Johnson (3)...............................  56  Director
</TABLE>

- ------------------------

(1) Member of Audit Committee.

(2) Member of Compensation Committee.

(3) Mr. Johnson has tendered his resignation as a director, effective October 5,
    1999.

    JEFFREY S. HUSSEY co-founded F5 in February 1996 and has been our Chairman,
Chief Executive Officer and President since that time. From February 1996 to
March 1999, Mr. Hussey also served as our Treasurer. From July 1995 to February
1996, Mr. Hussey served as Vice President of Alexander Hutton Capital L.L.C., an
investment banking firm. From September 1993 to July 1995, Mr. Hussey served as
President of Pacific Comlink, an inter-exchange carrier providing frame relay
and Internet access services to the Pacific Rim, which he founded in September
1993. Mr. Hussey holds a B.A. in Finance from Seattle Pacific University and an
M.B.A. from the University of Washington.

    ROBERT J. CHAMBERLAIN has served as our Vice President of Finance, Chief
Financial Officer and Treasurer since March 1999. From September 1998 to
February 1999, Mr. Chamberlain served as Senior Vice President and Chief
Financial Officer of Yesler Software, an early stage company developing a
personal multimedia web communication product. From February 1998 to July 1998,
Mr. Chamberlain served as Co-President of Photodisc, a provider of digital
imagery, which merged with Getty Images Inc. in February 1998. From May 1997 to
February 1998, Mr. Chamberlain served as Senior Vice President and Chief
Financial Officer of Photodisc. From April 1996 to May 1997, Mr. Chamberlain
served as Executive Vice President and Chief Financial Officer of Midcom
Communications Inc., a telecommunications service provider. From January 1992 to
December 1995, Mr. Chamberlain served as Vice President Finance and Operations
of ElseWare Corporation, a font technology company. From July 1989 to April
1991, Mr. Chamberlain was an audit partner in the high technology practice of
KPMG Peat Marwick, and was employed by KPMG Peat Marwick since January 1980. Mr.
Chamberlain holds a B.S. in Business Administration and Accounting from
California State University, Northridge.

    STEVEN GOLDMAN has served as our Vice President of Sales and Marketing since
July 1997 and our Senior Vice President of Sales, Marketing and Services since
July 1999. From December 1996 to February 1997, Mr. Goldman served as Vice
President, Enterprise Sales and Services, for Microtest, Inc., a network test
equipment and CD ROM server company, after its acquisition of Logicraft. From
March 1995 to December 1996, Mr. Goldman served as Executive Vice President,
North American Operations, for

                                       37
<PAGE>
Logicraft, a CD ROM server company, after its merger with Virtual Microsytems, a
CD ROM server company. From 1990 to March 1995, Mr. Goldman served as Vice
President of Sales for Virtual Microsystems. Mr. Goldman holds a B.A. in
Economics from the University of California at Berkeley.

    BRETT L. HELSEL has served as our Vice President of Product Development and
Chief Technology Officer since May 1998. From April to May 1998, Mr. Helsel
served as our Vice President of Advanced Product Architecture. From March 1997
to March 1998, Mr. Helsel served as Vice President, Product Development, for
Cybersafe, Inc., a provider of enterprise-wide network security solutions. From
April 1994 to October 1997, Mr. Helsel served as Site Development Manager for
Wall Data, a host connectivity software company. Mr. Helsel holds a B.S. in
Geophysics and Oceanography from the Florida Institute of Technology.

    CARLTON G. AMDAHL has served as one of our directors since May 1998. Mr.
Amdahl operates Amdahl Associates, a consulting firm specializing in technology
management, product strategy and system architecture. Mr. Amdahl has served as
President of Network Caching Technology L.L.C., a network caching company, since
February 1999 and as President and Chief Executive Officer of Inca Technology, a
network caching company, since October 1997. From 1985 to January 1996, Mr.
Amdahl served as Chairman of the board of directors and Chief Technical Officer
of NetFRAME Systems, a high performance network server company, which he founded
in 1985. Mr. Amdahl is a Stanford University Sloan Fellow and holds a B.S.
degree in Electrical Engineering and Computer Science from the University of
California, Berkeley and an M.S. in Management from Stanford University.

    KARL D. GUELICH has served as one of our directors since June 1999. Mr.
Guelich has been in private practice as a certified public accountant since his
retirement from Ernst & Young in 1993, where he served as the Area Managing
Partner for the Pacific Northwest offices headquartered in Seattle from October
1986 to November 1992. Mr. Guelich holds a B.S. degree in Accounting from
Arizona State University.

    ALAN J. HIGGINSON has served as one of our directors since May 1996. From
November 1995 to November 1998, Mr. Higginson served as President of Atrieva
Corporation, a provider of advanced data backup and retrieval technology. From
May 1990 to November 1995, Mr. Higginson served as Executive Vice President of
Worldwide Sales and Marketing for Sierra On-line, a developer of multimedia
software for the home personal computer market. From May 1990 to November 1995,
Mr. Higginson served as President of Sierra On-line's Bright Star division, a
developer of educational software. Mr. Higginson holds a B.S. in Commerce and an
M.B.A. from the University of Santa Clara.

    SONJA L. HOEL has served as one of our directors since August 1998. Ms. Hoel
has been a managing director and general partner of Menlo Ventures, a venture
capital firm, since July 1996 and has been employed by Menlo Ventures since July
1994. From August 1993 to April 1994, Ms. Hoel was an associate at the Edison
Venture Fund, a venture capital firm. From December 1991 to June 1993, Ms. Hoel
served as a business development consultant at Symantec Corporation, a consumer
software applications company, and from January 1989 to June 1991, served as an
investment analyst at TA Associates, a venture capital firm. Ms. Hoel holds a
B.S. in Commerce from the University of Virginia and an M.B.A from the Harvard
Business School.

    KENT L. JOHNSON has served as one of our directors since May 1996. Mr.
Johnson has tendered his resignation as a director of F5, effective October 5,
1999. Mr. Johnson is President of Alexander Hutton Capital, L.L.C., which he
co-founded in August 1994. From April 1989 to May 1994, Mr. Johnson served as
Senior Vice President and Chief Operating Officer of Brazier Forest Industries,
a forest products company. Mr. Johnson is also a director of Timeline, Inc., a
software company. Mr. Johnson holds a B.A. in Business Administration from the
University of Washington and an M.B.A. from Seattle University.

    Our executive officers are appointed by the board of directors and serve
until their successors are elected or appointed.

    There are no family relationships among any of our directors or executive
officers.

                                       38
<PAGE>
BOARD COMPOSITION

    We have authorized a range of directors from five to nine. In accordance
with the terms of our amended articles of incorporation, the terms of office of
the board of directors is divided into three classes:

    - Class I directors, whose term expires at the annual meeting of
      shareholders to be held in 2000;

    - Class II directors, whose term expires at the annual meeting of
      shareholders to be held in 2001; and

    - Class III directors, whose term expires at the annual meeting of
      shareholders to be held in 2002.

    Our Class I directors are Mr. Guelich and Ms. Hoel, our Class II directors
are Messrs. Higginson and Johnson, and our Class III directors are Messrs.
Amdahl and Hussey. At each annual meeting of shareholders after the initial
classification, the successors to directors whose terms will then expire will be
elected to serve from the time of election and qualification until the third
annual meeting following election. Any additional directorships resulting from
an increase in the number of directors will be distributed among the three
classes so that, as nearly as possible, each class will consist of one-third of
the directors. This classification of the board of directors may have the effect
of delaying or preventing changes in control or management of F5.

BOARD COMMITTEES

    - AUDIT COMMITTEE. Our audit committee, consisting of Mr. Amdahl and Mr.
      Guelich, reviews our internal accounting procedures and consults with and
      reviews the services provided by our independent auditors.

    - COMPENSATION COMMITTEE. Our compensation committee, consisting of Ms. Hoel
      and Messrs. Higginson and Guelich, reviews and recommends to the board of
      directors the compensation and benefits of all our officers and
      establishes and reviews general policies relating to compensation and
      benefits of our employees. Mr. Hussey, who acts as a plan administrator
      for our 1998 Equity Incentive Plan, authorizes stock option grants for
      employees other than officer and director level employees within ranges
      pre-approved by the board of directors.

COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION

    None of our executive officers serves as a member of the board of directors
or compensation committee of any entity that has one or more executive officers
serving as a member of our board of directors or compensation committee.

DIRECTOR COMPENSATION

    Directors currently receive no cash compensation from F5 for their services
as members of the board of directors. They are reimbursed for certain expenses
in connection with attendance at board and committee meetings. From time to
time, certain non-employee directors have received grants of options to purchase
shares of our common stock. In May 1996, Messrs. Higginson and Johnson each were
granted an option to purchase 84,000 shares of our common stock at an exercise
price of $0.50 per share. In May 1998, Mr. Amdahl was granted an option to
purchase 84,000 shares of our common stock at an exercise price of $0.50 per
share. Eligible non-employee directors receive automatic option grants under our
1999 Non-Employee Directors' Option Plan at the fair market value of our common
stock on the date of grant. In June, 1999, Mr. Guelich was granted an option
under this plan to purchase 5,000 shares of our common stock at an exercise
price of $18.00 per share. See "--Equity Incentive Plans--Amended and Restated
Directors' Nonqualified Stock Option Plan" and "--1999 Non-Employee Directors'
Option Plan."

                                       39
<PAGE>
EXECUTIVE COMPENSATION

    The table below sets forth the compensation paid by us during the fiscal
year ended September 30, 1998 to (a) our President and Chief Executive Officer
and (b) our only other executive officer other than the Chief Executive Officer
whose salary and bonus for fiscal 1998 exceeded $100,000 and who served as an
executive officer of F5 during the fiscal year ended September 30, 1998.

                           SUMMARY COMPENSATION TABLE

<TABLE>
<CAPTION>
                                                    ANNUAL COMPENSATION
                                                    --------------------
NAME AND PRINCIPAL POSITION                          SALARY      BONUS    ALL OTHER COMPENSATION
- --------------------------------------------------  ---------  ---------  -----------------------
<S>                                                 <C>        <C>        <C>
Jeffrey S. Hussey.................................  $ 128,749  $   3,196                --
  President and Chief Executive Officer

Steven Goldman....................................    120,000      5,000         $  46,444(1)
  Senior Vice President of Sales, Marketing and
    Services
</TABLE>

- ------------------------

(1) Represents commissions paid to Mr. Goldman in fiscal 1998.

OPTION GRANTS IN LAST FISCAL YEAR

    We did not grant any options to the executive officers shown in the Summary
Compensation Table above in fiscal 1998.

FISCAL YEAR-END OPTION VALUES

    The following table sets forth for the executive officers shown in the
Summary Compensation Table the aggregate dollar value realized upon exercise of
stock options in the last fiscal year and number and value of securities
underlying unexercised options held at September 30, 1998.

<TABLE>
<CAPTION>
                                                                                               VALUE OF UNEXERCISED
                                                          NUMBER OF SECURITIES                IN-THE-MONEY OPTIONS AT
                                                     UNDERLYING UNEXERCISED OPTIONS         SEPTEMBER 30, 1998 ($) (1)
                                         VALUE           AT SEPTEMBER 30, 1998          -----------------------------------
                     SHARES ACQUIRED   REALIZED   ------------------------------------                      UNEXERCISABLE
NAME                 ON EXERCISE (#)    ($) (1)    EXERCISABLE (#)   UNEXERCISABLE (#)   EXERCISABLE ($)         ($)
- ------------------  -----------------  ---------  -----------------  -----------------  -----------------  ----------------
<S>                 <C>                <C>        <C>                <C>                <C>                <C>
Jeffrey S.
  Hussey..........             --             --             --                 --                 --                 --
Steven Goldman....         59,250      $ 589,538             --            177,750(2)              --         $1,768,613
</TABLE>

- --------------------------

(1) Based on the initial public offering price of $10.00 per share less the
    exercise price, multiplied by the number of shares underlying the option.

(2) These options vest 25% on each of the first, second, third and fourth
    anniversary of the grant date. These options will vest fully if we are
    acquired in a merger or asset sale. All of these options have a ten-year
    term.

INCENTIVE STOCK PLANS

    1998 EQUITY INCENTIVE PLAN.  Our board of directors adopted our 1998 Equity
Incentive Plan on October 22, 1998, and our shareholders approved it on November
12, 1998. We initially reserved a total of 800,000 shares for issuance under the
plan. In April 1999 we reserved an additional 1,500,000 shares for issuance
under the plan and the shareholders approved it in May, 1999. The plan provides
for grants of incentive stock options that qualify under Section 422 of the
Internal Revenue Code of 1986, as amended, to employees, including officers, of
F5 or any affiliate of F5, and nonstatutory stock options, restricted stock
purchase awards, and stock bonuses to employees, including officers, or
directors of and consultants to F5 or any affiliate of F5. The board or a
committee appointed by the board administers the plan. Our

                                       40
<PAGE>
board has the authority to determine which recipients and what types of awards
are to be granted, including the exercise price, number of shares subject to the
award and the exercisability of the awards.

    The term of a stock option granted under the plan generally may not exceed
10 years. The board of directors determines the exercise price of options
granted under the plan. However, in the case of an incentive stock option, the
exercise price cannot be less than 100% of the fair market value of our common
stock on the date of grant and, in the case of a nonstatutory stock option, the
exercise price cannot be less than 50% of the fair market value of our common
stock on the date of grant. Options granted under the plan vest at the rate
specified in the option agreement. Except as expressly provided by the terms of
a nonstatutory stock option agreement, an optionee may not transfer options
other than by will or the laws of descent or distribution, provided that an
optionee may designate a beneficiary who may exercise the option following the
optionee's death. An optionee whose relationship with us or any related
corporation ceases for any reason, except by death or permanent and total
disability, generally may exercise vested options up to three months following
cessation. Vested options may generally be exercised for up to 12 months after
an optionee's relationship with F5 or any affiliate of F5 ceases due to
disability and for generally up to 18 months after the relationship with F5 or
any affiliate of F5 ceases due to death. However, options may terminate or
expire sooner or later as may be determined by the board and set forth in the
option agreement.

    No incentive stock option may be granted to any person who, at the time of
the grant, owns, or is deemed to own, stock possessing more than 10% of the
total combined voting power of F5 or any affiliate of F5, unless the option
exercise price is at least 110% of the fair market value of the stock subject to
the option on the date of grant and the term of the option does not exceed five
years from the date of grant. In addition, the aggregate fair market value,
determined at the time of grant, of the shares of our common stock with respect
to which incentive stock options are exercisable for the first time by an
optionee during any calendar year under the plan and all other stock plans of F5
and its affiliates may not exceed $100,000. The options, or portions of the
options, which exceed this limit are treated as nonstatutory options.

    No person may be granted options under the plan covering an aggregate of
more than 200,000 shares of our common stock in any calendar year.

    Shares subject to stock awards that have lapsed or terminated, without
having been exercised in full, may again become available for the grant of
awards under the plan.

    Restricted stock purchase awards granted under the plan may be granted
pursuant to a repurchase option in our favor in accordance with a vesting
schedule determined by the board. The purchase price of these awards will be at
least 50% of the fair market value of our common stock on the date of grant.
Stock bonuses may be awarded in consideration for past services. Rights under a
stock bonus or restricted stock purchase agreement may not be transferred other
than by will or by the laws of descent and distribution unless the stock bonus
or restricted stock purchase agreement specifically provides for
transferability.

    Upon certain changes in control of F5 as provided under the plan, the
surviving entity will either assume or substitute all outstanding stock awards
under the plan. If the surviving entity determines not to assume or substitute
these awards, then with respect to persons whose service with F5 or an affiliate
of F5 has not terminated before the change in control, the vesting of 50% of
these stock awards (and the time during which these awards may be exercised)
will accelerate and the awards terminated if not exercised before the change in
control.

    As of August 31, 1999, we had issued 169,291 shares upon the exercise of
options granted under the plan and options to purchase 687,765 shares were
outstanding with 1,442,944 shares reserved for future grants or purchases under
the plan. The plan will terminate on October 21, 2008, unless terminated sooner
by the board.

    AMENDED AND RESTATED 1996 STOCK OPTION PLAN.  Our board of directors adopted
the Amended and Restated 1996 Stock Option Plan on December 2, 1996, and our
shareholders approved it on January 28,

                                       41
<PAGE>
1997. We have reserved a total of 2,600,000 shares for issuance under the plan,
less any shares issuable upon the exercise of options granted under the Amended
and Restated Directors' Nonqualified Stock Option Plan. The plan provides for
grants of incentive stock options that qualify under Section 422 of the Internal
Revenue Code to employees, including officers and employee directors, of F5 or
any affiliate of F5 and nonstatutory stock options to employees, consultants and
other persons selected by the board. The board or a committee appointed by the
board administers the plan. The board has the authority to determine which
recipients and what types of options are to be granted, including the exercise
price, number of shares subject to the option and the exercisability of the
options.

    The term of a stock option granted under the plan generally may not exceed
10 years. The exercise price of incentive stock options and non-statutory stock
options granted under the plan following the offering, will not be less than
100% of the fair market value of our common stock on the date of grant. Options
granted under the plan vest at the rate specified in the option agreement,
provided that options will vest as to 25% of the underlying shares each year
following the date of grant if vesting is not specified in the option agreement.
An optionee may not transfer any options other than by will or the laws of
descent or distribution. If an optionee's service terminates due to death or
disability, then any option held by this optionee who F5 or an affiliate of F5
has continuously employed for two years will automatically become fully vested
and be exercisable for the duration of the option term.

    An optionee whose relationship with F5 or any affiliate of F5 ceases for any
reason, other than by death or permanent and total disability, may exercise
vested options up to 90 days following the cessation or a longer period as may
be extended by the board in the case of a nonstatutory stock option. Options may
be exercised for up to 12 months after an optionee's relationship with F5 or its
affiliate ceases due to death or disability or a longer period as the board of
directors may extend in the case of a nonstatutory stock option.

    No incentive stock option may be granted to any person who, at the time of
the grant, owns, or is deemed to own, stock possessing more than 10% of the
total combined voting power of F5 or any affiliate of F5, unless the option
exercise price is at least 110% of the fair market value of the stock subject to
the option on the date of grant and the term of the option does not exceed five
years from the date of grant. In addition, the aggregate fair market value,
determined at the time of grant, of the shares of our common stock with respect
to which incentive stock options are exercisable for the first time by an
optionee during any calendar year under the plan and all other stock plans of F5
and its affiliates may not exceed $100,000. The options, or portions of the
options, which exceed this limit are treated as nonstatutory options.

    Shares subject to stock options that have lapsed or terminated, without
having been exercised in full, may again become available for the grant of
options under the plan.

    Upon certain changes of control of F5 as provided under the plan, or in the
case of a dividend in excess of 10% of the then fair market value of our stock,
all outstanding options will automatically become fully vested and exercisable
for the duration of the option term.

    As of August 31, 1999, we had issued 749,750 shares upon the exercise of
options granted under the plan and options to purchase 1,579,640 shares were
outstanding with 102,610 shares reserved for future grants under either this
plan or our Amended and Restated Directors' Nonqualified Stock Option Plan. We
do not plan to grant any additional options under this plan.

    AMENDED AND RESTATED DIRECTORS' NONQUALIFIED STOCK OPTION PLAN.  Our board
of directors adopted the Amended and Restated Directors' Nonqualified Stock
Option Plan on December 2, 1996, and our shareholders approved it on January 28,
1997. The plan provides for the issuance of up to 2,600,000 shares of our common
stock, less the number of any shares issuable upon exercise under the Amended
and Restated 1996 Stock Option Plan. All of our non-employee directors who
joined our board of directors before August 21, 1998 were entitled to receive
non-discretionary stock option grants under the plan. Options granted under the
plan do not qualify as incentive stock options under the Internal Revenue

                                       42
<PAGE>
Code. Each option granted pursuant to the plan has an exercise price equal to
$0.50. Under the plan, each non-employee director who joined the board following
the closing of the offering of our Series A preferred stock and before May 1,
1998 and who was not elected in direct connection with his or her investment in
our stock (or with the investment in our stock by an affiliated or
representative entity of the non-employee director) was automatically granted an
option to purchase that number of shares of our common stock equal to one
percent of the then-current fully-diluted number of shares of our common stock.
After May 1, 1998, each newly appointed non-employee director was automatically
granted an option to purchase 84,000 shares of our common stock. Options granted
under the plan vest in three equal annual installments from the date of grant
and become immediately vested and exercisable upon a director's death or
disability. Options granted under the plan are generally non-transferable. An
optionee whose directorship with F5 ceases for any reason, other than by death
or disability, may exercise vested options up to 90 days following cessation,
unless these options terminate or expire sooner by their terms. Options may be
exercised for up to one year after an optionee's directorship with F5 ceases due
to disability or death. An optionee may not exercise any options granted under
the plan, however, after the expiration of ten years from the date it was
granted. Upon certain changes of control of F5 as provided under the plan, the
plan's options will automatically become fully vested and be exercisable for the
duration of the option term.

    As of August 31, 1999, we had issued 126,000 shares upon the exercise of
options granted under the plan, and options to purchase 168,000 shares were
outstanding with 102,610 shares reserved for future grants or purchases under
either this plan or the 1996 Stock Option Plan. We do not plan to grant any
additional options under the Amended and Restated Directors' Nonqualified Stock
Option Plan.

    1999 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN.  We adopted the 1999
Non-Employee Directors' Stock Option Plan in April 1999 to provide for the
automatic grant to F5 non-employee directors of options to purchase shares of
our common stock. The board administers the plan unless it has delegated
administration to a committee. In April 1999, we reserved an aggregate of
100,000 shares of common stock for issuance under the plan, subject to
adjustment in the event of certain capital changes, and the shareholders
approved it in May, 1999.

    Each person who is first elected or appointed as a non-employee director
after the initial public offering will automatically receive a fully vested and
exercisable option for 5,000 shares. In addition, on the day after each of our
annual meetings of the shareholders, starting with the annual meeting in 2000,
each eligible non-employee director will automatically receive a fully vested
and exercisable option for 5,000 shares, provided that the recipient has been a
non-employee director for at least the prior six months. As long as a
non-employee director who is an optionholder continues to serve with us or with
an affiliate of ours, whether in the capacity of a director, an employee or a
consultant, the optionholder may exercise the option.

    The optionholder may not transfer the option except by will or by the laws
of descent and distribution. Although only the optionholder may exercise the
option during his or her lifetime, the optionholder may designate a third party
who may exercise the option in the event of the optionee's death. Options
granted under the plan expire 10 years after the date of grant and have an
exercise price equal to 100% of the fair market value of the common stock on the
date of grant. If the optionholder's service to F5 or an affiliate terminates,
the optionholder may exercise the option for 12 months if termination is due to
disability, for 18 months if termination is due to death or for three months in
all other circumstances.

    In the event of a "change in control," the surviving or acquiring
corporation may assume outstanding options under the plan or substitute similar
options. A "change in control" means a sale of all or substantially all of F5's
assets, a merger or consolidation in which F5 is not the surviving corporation
or a reverse merger in which F5 is the surviving corporation but the shares of
common stock outstanding immediately preceding the merger are converted by
virtue of the merger into other property.

    1999 EMPLOYEE STOCK PURCHASE PLAN.  In April 1999, we adopted the 1999
Employee Stock Purchase Plan, authorizing the issuance of 1,000,000 shares of
common stock pursuant to purchase rights granted to

                                       43
<PAGE>
employees of F5 or to employees of any designated affiliate of F5 and the
shareholders approved it in May, 1999. The purchase plan is intended to qualify
as an employee stock purchase plan within the meaning of Section 423 of the
Internal Revenue Code.

    The purchase plan provides a means by which employees may purchase our
common stock through payroll deductions. We implement this purchase plan by
offerings of purchase rights to eligible employees. Under the purchase plan, we
may specify offerings with a duration of not more than 27 months, and may
specify shorter purchase periods within each offering. The first offering began
on June 4, 1999. Unless otherwise determined by the board of directors, common
stock is purchased for accounts of employees participating in the purchase plan
at a price per share equal to the lower of (1) 85% of the fair market value of a
share of common stock on the first day of the offering or (2) 85% of the fair
market value of a share of common stock on the date of purchase.

    Generally, employees who work at least 20 hours per week and 5 months per
calendar year may deduct up to 15% of their base compensation for the purchase
of stock under the purchase plan. Employees may end their participation in the
offering at any time up to one day before the offering ends. Participation ends
automatically on termination of employment with F5 or an affiliate.

    We may grant eligible employees purchase rights under this plan only if the
rights together with any other rights granted under other employee stock
purchase plans established by F5 or an affiliate of F5, if any, do not permit
the employee's rights to purchase our stock to accrue at a rate which exceeds
$25,000 of fair market value of this stock for each calendar year in which these
rights are outstanding. No employee is eligible for the grant of any rights
under the purchase plan if immediately after we grant these rights, the employee
has voting power over 5% or more of our outstanding capital stock. As of the
date hereof, no shares of common stock had been purchased under the purchase
plan.

    401(k) PLAN.  We have adopted a tax-qualified employee savings and
retirement plan, the 401(k) Plan, for eligible United States employees. Eligible
employees may elect to defer a percentage of their eligible compensation in the
401(k) Plan, subject to the statutorily prescribed annual limit. We may make
matching contributions on behalf of all participants in the 401(k) Plan in an
amount determined by our board of directors. We may also make additional
discretionary profit sharing contributions in amounts as determined by the board
of directors, subject to statutory limitations. Matching and profit-sharing
contributions, if any, are subject to a vesting schedule; all other
contributions are at all times fully vested. We intend the 401(k) Plan, and the
accompanying trust, to qualify under Sections 401(k) and 501 of the Internal
Revenue Code so that contributions by employees or by F5 to the 401(k) Plan, and
income earned (if any) on plan contributions, are not taxable to employees until
withdrawn from the 401(k) Plan, and so that we will be able to deduct our
contributions, if any, when made. The trustee under the 401(k) Plan, at the
direction of each participant, invests the assets of the 401(k) Plan in any of a
number of investment options.

LIMITATIONS OF LIABILITY AND INDEMNIFICATION MATTERS

    Our articles of incorporation limit the liability of directors to the
fullest extent permitted by the Washington Business Corporation Act as it
currently exists. Consequently, subject to the Washington Business Corporation
Act, no director will be personally liable to us or our shareholders for
monetary damages resulting from his or her conduct as a director of F5, except
liability for:

    - acts or omissions involving intentional misconduct or knowing violations
      of law;

    - unlawful distributions; or

    - transactions from which the director personally receives a benefit in
      money, property or services to which the director is not legally entitled.

    Our articles of incorporation provide that we may indemnify any individual
made a party to a proceeding because that individual is or was an F5 director or
officer, and this right to indemnification will

                                       44
<PAGE>
continue as to an individual who has ceased to be a director or officer and will
inure to the benefit of his or her heirs, executors or administrators. Any
repeal of or modification to our articles of incorporation may not adversely
affect any right of an F5 director or officer who is or was a director or
officer at the time of any repeal or modification. To the extent the provisions
of our articles of incorporation provide for indemnification of directors or
officers for liabilities arising under the Securities Act of 1933, as amended,
those provisions are, in the opinion or the Securities and Exchange Commission,
against public policy as expressed in the Securities Act and they are therefore
unenforceable.

    Our bylaws provide that we will indemnify our directors and officers and may
indemnify our other officers and employees and other agents to the fullest
extent permitted by law.

    We have entered into agreements to indemnify our directors and certain
officers, in addition to indemnification provided for in our articles of
incorporation or bylaws. These agreements, among other things, indemnify our
directors and certain officers for certain expenses, including attorneys' fees,
judgments, fines and settlement amounts incurred by any of these persons in any
action or proceeding, including any action by us arising out of the person's
services as our director or officer or any other company or enterprise to which
the person provides services at our request. We believe that these provisions
and agreements are necessary to attract and retain qualified persons as
directors and officers. We also currently maintain liability insurance for our
officers and directors.

CHANGE OF CONTROL ARRANGEMENTS

    Upon certain changes in control of F5 as provided under the 1998 Equity
Incentive Plan, all outstanding stock awards under this plan will either be
assumed or substituted by the surviving entity. If the surviving entity
determines not to assume or substitute these awards, then with respect to
persons whose service with F5 or an affiliate of F5 has not terminated before
the change in control, the vesting of 50% of these stock awards and the time
during which these awards may be exercised will be accelerated and the awards
terminated if not exercised before the change in control.

    Upon certain changes of control of F5 as provided under the Amended and
Restated 1996 Stock Option Plan, or in the case of a dividend in excess of 10%
of the then fair market value of our stock, then all outstanding options under
this plan will automatically become fully vested and exercisable for the
duration of the option term.

    Upon certain changes of control of F5 as provided under the Amended and
Restated Directors' Nonqualified Stock Option Plan, all outstanding options will
automatically become fully vested and be exercisable for the duration of the
option term.

    Pursuant to the terms of an agreement between F5 and Mr. Goldman, in the
event of a business combination in which F5 is not the surviving entity, if the
surviving entity terminates Mr. Goldman as Senior Vice President of Sales,
Marketing and Services or changes his position to one that is not equal or
greater in scope, responsibility, compensation or stature, then Mr. Goldman may
be entitled to a severance payment equal to his 1998 compensation.

                                       45
<PAGE>
                              CERTAIN TRANSACTIONS

    Since our incorporation in February 1996 through August 31, 1999, we have
issued and sold securities to the following persons who are our executive
officers, directors or principal shareholders.

<TABLE>
<CAPTION>
                            SERIES A     SERIES B     SERIES C     SERIES D
                            PREFERRED    PREFERRED    PREFERRED    PREFERRED    WARRANTS     COMMON
INVESTOR (1)                STOCK (2)    STOCK (3)    STOCK (4)    STOCK (5)       (6)        STOCK
- -------------------------  -----------  -----------  -----------  -----------  -----------  ---------
<S>                        <C>          <C>          <C>          <C>          <C>          <C>
Carlton G. Amdahl........          --           --           --           --           --      28,000
Robert J. Chamberlain....          --           --           --           --           --     150,000
Steven Goldman...........          --           --           --           --           --      92,250
Brett Helsel.............          --           --           --           --           --      50,000
Alan J. Higginson........      10,000           --           --           --           --          --
Jeffrey S. Hussey........          --           --           --           --           --   3,448,000
Kent L. Johnson..........      10,000(7)         --          --           --           --      56,000
Michael D. Almquist......          --           --           --           --           --   1,480,000
Britannia Holdings
  Limited................          --      937,500           --           --    1,825,000     600,000
Cypress Partners Limited
  Partnership............          --           --      156,250           --           --     187,500
Encompass Group
  Incorporated...........     100,000      156,250           --           --      187,500          --
Menlo Ventures (8).......          --           --           --      843,926           --          --
Alexander Hutton Capital,
  L.L.C. (9).............          --           --           --           --           --     240,000
</TABLE>

- ------------------------

 (1) See "Principal and Selling Shareholders" for more detail on shares held by
     these purchasers.

 (2) The per share purchase price for our Series A preferred stock was $3.00.
     Each outstanding share of Series A preferred stock has been converted into
     six shares of common stock at a conversion price of $0.50 per share.

 (3) The per share purchase price for our Series B preferred stock was $1.60.
     Each outstanding share of Series B preferred stock has been converted into
     two shares of common stock at a conversion price of $0.80 per share.

 (4) The per share purchase price for our Series C preferred stock was $9.60.
     Each outstanding share of Series C preferred stock has been converted into
     six shares of common stock at a conversion price of $1.60 per share.

 (5) The per share purchase price for our Series D preferred stock was $6.79.
     Each outstanding share of Series D preferred stock has been converted into
     two shares of common stock at a conversion price of $3.395 per share.

 (6) Warrants are exercisable for our common stock at purchase prices per share
     as follows:

<TABLE>
<CAPTION>
WARRANTS                                                                                  PRICE
- --------------------------------------------------------------------------------------  ---------
<S>                                                                                     <C>
 600,000..............................................................................  $    0.50
 100,000..............................................................................  $    0.64
1,312,500.............................................................................  $    0.80
</TABLE>

 (7) Consists of 10,000 shares held by KLJ Ventures, of which Mr. Johnson is
     President.

 (8) The shares listed represent 809,910 shares held by Menlo Ventures VII, L.P.
     and 34,016 shares held by Menlo Entrepreneurs Fund VII, L.P. Ms. Hoel, one
     of our directors, is a managing director and general partner of Menlo
     Ventures.

 (9) Mr. Johnson, one of our directors, is President of Alexander Hutton
     Capital, L.L.C.

                                       46
<PAGE>
    In addition, we have granted options to certain of our executive officers.
See "Management-- Executive Compensation."

    In May, August and December 1996, we sold an aggregate of 400,000 shares of
Series A Preferred stock to certain investors, including Messrs. Higginson and
Johnson, two of our directors, members of the Hussey family, and Encompass Group
Limited, one of our principal shareholders, at an aggregate purchase price of
$1.2 million or $3.00 per share. We paid Alexander Hutton Capital, L.L.C. a
placement agent fee of $70,000 in connection with the sale of our Series A
preferred stock. Mr. Johnson, one of our directors, is President of Alexander
Hutton Capital, L.L.C.

    In March and August of 1997, we issued Brittania Holdings a warrant
exercisable for 100,000 and 600,000 shares of common stock in conjunction with
convertible note agreements of $500,000 and $300,000, respectively. The warrants
have per share exercise prices of $0.64 and $0.50, respectively.

    In September, October and November 1997, we sold an aggregate of 1,250,000
shares of Series B preferred stock to certain investors, including Brittania
Holdings and Encompass Group Limited, two of our principal shareholders, at an
aggregate purchase price of $2.0 million or $1.60 per share. We also issued
Brittania Holdings a warrant exercisable for 1,125,000 shares of common stock at
a per share exercise price of $0.80 and Encompass Group Limited a warrant
exercisable for 187,500 shares of common stock at a per share exercise price of
$0.80.

    On April 15, 1998, we sold an aggregate of 156,250 shares of Series C
preferred stock to Cypress Partners Limited Partnership at an aggregate purchase
price of $1.5 million or $9.60 per share, and issued Cypress Partners Limited
Partnership a warrant exercisable for 187,500 shares of common stock at a per
share exercise price of $1.60, which was exercised on February 1, 1999.

    On August 21, 1998, we sold an aggregate of 1,138,438 shares of Series D
preferred stock to certain investors, including affiliates of Menlo Ventures and
IDG Ventures, two of our principal shareholders, at an aggregate purchase price
of $7.7 million or $6.79 per share. Ms. Hoel, one of our directors, is a
managing director and general partner of Menlo Ventures.

    In March 1999, we issued 150,000 shares of our common stock to Mr.
Chamberlain in exchange for a promissory note. These shares were acquired by
exercising stock options that vest over a period of four years. The note bears
interest at a rate of 4.83%, is collateralized by the shares and partially
guaranteed by Mr. Chamberlain and is due in 2003. Under the pledge agreement, we
have the obligation to repurchase any remaining unvested shares, and the note
becomes due upon Mr. Chamberlain's termination. Further, the shares may not be
transferred until they are vested and paid for except under certain
circumstances as provided under the pledge agreement.

    We have entered into indemnification agreements with our directors and
certain officers for the indemnification of and advancement of expenses to these
persons to the fullest extent permitted by law. We also intend to enter into
these agreements with our future directors and certain officers.

    We believe that the foregoing transactions were in our best interest and
were made on terms no less favorable to us than could have been obtained from
unaffiliated third parties. All future transactions between us and any of our
officers, directors or principal shareholders will be approved by a majority of
the independent and disinterested members of the board of directors, will be on
terms no less favorable to us than could be obtained from unaffiliated third
parties and will be in connection with our bona fide business purposes.

                                       47
<PAGE>
                       PRINCIPAL AND SELLING SHAREHOLDERS

    The following table summarizes certain information regarding the beneficial
ownership of our outstanding common stock as of August 31, 1999 for:

    - each person or group that we know owns more than 5% of the common stock;

    - each of our directors;

    - our chief executive officer;

    - executive officers whose compensation exceeded $100,000 in 1998;

    - a shareholder who is selling shares in this offering; and

    - all of our directors and executive officers as a group.

<TABLE>
<CAPTION>
                                                               SHARES BENEFICIALLY
                                                                  OWNED PRIOR TO                       SHARES BENEFICIALLY
                                                                     OFFERING           NUMBER OF      OWNED AFTER OFFERING
                                                              ----------------------   SHARES BEING   ----------------------
NAME AND ADDRESS (1)                                           NUMBER    PERCENT (2)     OFFERED       NUMBER    PERCENT (2)
- ------------------------------------------------------------  ---------  -----------   ------------   ---------  -----------
<S>                                                           <C>        <C>           <C>            <C>        <C>
5% SHAREHOLDERS
Michael D. Almquist ........................................  1,340,000       7.6%      100,000       1,240,000      6.7%
  153 Highland Drive
  Seattle, Washington 98109
Britannia Holdings Limited (3) .............................  3,950,000      19.8       800,000       3,150,000     16.9
  P.O. Box 556
  Main Street
  Charlestown, Nevis
Menlo Ventures VII, L.P. (4) ...............................  1,687,852       9.3       250,000       1,437,852      7.7
  3000 Sand Hill Rd., Bldg. 4-100
  Menlo Park, California 94025
Cypress Partners Limited Partnership .......................  1,125,000       6.2            --       1,125,000      6.0
  P.O. Box 9006
  Seattle, Washington 98109
Encompass Ventures, Inc. (5) ...............................  1,100,000       6.1            --       1,100,000      5.9
  777 - 108th Avenue N.E., Suite 2300
  Bellevue, Washington 98004
CURRENT EXECUTIVE OFFICERS AND DIRECTORS
Jeffrey S. Hussey (6).......................................  2,618,000      14.4       100,000       2,518,000     13.5
Steven Goldman (7)..........................................    206,110       1.1        40,000         166,110     *
Carlton G. Amdahl...........................................     28,000     *                --          28,000     *
Karl D. Guelich (8).........................................      5,000     *                --           5,000     *
Alan J. Higginson (9).......................................    141,300     *                --         141,300     *
Sonja L. Hoel (4)...........................................  1,687,852       9.3       250,000       1,437,852      7.7
Kent L. Johnson (10)........................................    170,740     *                --         170,740     *
All directors and executive officers as a group (9 persons)
  (11)......................................................  5,136,410      27.9       420,000       4,716,410     25.3
OTHER SELLING SHAREHOLDERS
Brian R. Dixon..............................................    125,687     *            20,000         105,687     *
Brett L. Helsel.............................................     80,000     *            30,000          50,000     *
Taylor Hussey Trust.........................................    400,000       2.1        50,000         350,000      1.9
Becky Arnett Hussey.........................................    350,000       1.9        35,000         315,000      1.7
Gerald W. Hussey and Helen J. Hussey........................    140,000     *            20,000         120,000     *
Gary Pittman................................................    187,500       1.1        50,000         137,500     *
Joann M. Reiter.............................................     13,600     *             5,000           8,600     *
</TABLE>

- ------------------------

   * Less than 1%

                                       48
<PAGE>
 (1) Unless otherwise indicated, the address of each of the named individuals is
     c/o F5 Networks, Inc., 200 First Avenue West, Suite 500, Seattle,
     Washington 98119

 (2) Beneficial ownership of shares is determined in accordance with the rules
     of the Securities and Exchange Commission and generally includes any shares
     over which a person exercises sole or shared voting or investment power, or
     of which a person has the right to acquire ownership at any time within 60
     days after August 31, 1999. Except as otherwise indicated, and subject to
     applicable community property laws, the persons named in the table have
     sole voting and investment power with respect to all shares of common stock
     held by them. Applicable percentage ownership in the following table is
     based on 18,126,667 shares of common stock outstanding as of August 31,
     1999 and 18,626,667 shares of common stock outstanding immediately
     following the completion of this offering.

 (3) The Duvall Trust is the sole shareholder of Britannia Holdings Limited. The
     Elfin Trust Company Limited, a Guernsey corporation, is the trustee of the
     Duvall Trust. Mr. Peter Howe is the trustee for the Elfin Trust Company
     Limited. Includes 1,825,000 shares issuable upon exercise of warrants
     exercisable within 60 days of August 31, 1999.

 (4) Ms. Hoel is a managing director and general partner of Menlo Ventures. The
     shares listed represent 1,619,820 shares held by Menlo Ventures VII, L.P.
     and 68,032 shares held by Menlo Entrepreneurs Fund VII, L.P. Ms. Hoel
     disclaims beneficial ownership of all shares held by Menlo Entrepreneurs
     Fund VII, L.P. except to the extent of her pro rata interest in this
     partnership. The shares being offered for sale are being offered by Menlo
     Ventures.

 (5) Includes 187,500 shares issuable upon warrants exercisable within 60 days
     of August 31, 1999.

 (6) Does not include 400,000 shares held by Brian Dixon as trustee of the
     Hussey Family Trust fbo Mr. Hussey's minor child and 48,000 shares
     transferred to Mr. Hussey's brother in May 1999.

 (7) Includes 113,860 shares issuable upon exercise of options exercisable
     within 60 days of August 31, 1999.

 (8) Includes 5,000 shares issuable upon exercise of options exercisable within
     60 days of August 31, 1999.

 (9) Includes 84,000 shares issuable upon exercise of options exercisable within
     60 days of August 31, 1999.

 (10) Includes 28,000 shares issuable upon exercise of options exercisable
      within 60 days of August 31, 1999.

 (11) Includes 150,000 shares subject to repurchase by F5 and 280,268 shares
      issuable upon exercise of options exercisable within 60 days of August 31,
      1999.

                                       49
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK

GENERAL

    We have authorized 100,000,000 shares of common stock, no par value, and
10,000,000 shares of undesignated preferred stock, no par value. The following
description of our capital stock does not purport to be complete and is subject
to and qualified in its entirety by our second amended and restated articles of
incorporation and bylaws and by the provisions of applicable Washington law.

COMMON STOCK

    As of August 31, 1999, there were 18,126,667 shares of common stock
outstanding, which were held by 170 shareholders. Holders of common stock are
entitled to one vote per share on all matters to be voted upon by the
shareholders. Holders of common stock do not have cumulative voting rights, and,
therefore, holders of a majority of the shares voting for the election of
directors will be able to elect all of the directors.

    Holders of common stock will receive such dividends as our board of
directors may declare from time to time out of funds legally available for the
payment of dividends, subject to the terms of any existing or future agreements
between us and our debtholders. See "Dividend Policy." In the event of the
liquidation, dissolution or winding up of F5, the holders of common stock will
share ratably in all assets legally available for distribution after payment of
all debts and other liabilities and subject to the prior rights of any holders
of preferred stock then outstanding. Holders of our common stock have no
preemptive rights and no right to convert their common stock into any other
securities. There are no redemption or sinking fund provisions applicable to the
common stock. All outstanding shares of common stock are, and all shares of
common stock to be outstanding upon completion of this offering will be, fully
paid and nonassessable.

PREFERRED STOCK

    We have authorized 10,000,000 shares of undesignated preferred stock. There
are no shares of preferred stock outstanding. The board of directors has the
authority to issue the preferred stock in one or more series and to fix the
price, rights, preferences, privileges and restrictions thereof, including
dividend rights, dividend rates, conversion rights, voting rights, terms of
redemption, redemption prices, liquidation preferences and the number of shares
constituting a series or the designation of the series, without any further vote
or action by our shareholders. The issuance of preferred stock, while providing
desirable flexibility in connection with possible acquisitions and other
corporate purposes, could have the effect of delaying, deferring or preventing a
change in control of F5 without further action by the shareholders and may
adversely affect the market price of, and the voting and other rights of, the
holders of common stock. The issuance of preferred stock with voting and
conversion rights may adversely affect the voting power of the holders of common
stock, including the loss of voting control to others. We have no current plans
to issue any shares of preferred stock.

WARRANTS

    As of August 31, 1999, warrants to purchase 2,212,500 shares of common stock
were outstanding at a weighted-average exercise price of $0.75 per share. Each
warrant contains provisions for the adjustment of the exercise price and the
aggregate number of shares issuable upon the exercise of the warrant in the
event of stock dividends, stock splits, reorganizations, reclassifications and
consolidations. Warrants exercisable for an aggregate of 2,200,000 shares of
common stock contain additional provisions for the adjustment of the exercise
price and the aggregate number of shares issuable upon certain dilutive
issuances of securities at prices below the then existing warrant exercise
price.

                                       50
<PAGE>
REGISTRATION RIGHTS

    Holders of 5,364,376 shares of common stock and of warrants exercisable for
2,200,000 shares of common stock have certain rights relating to the
registration of these shares under state and federal securities laws. These
rights, which are assignable, are outlined in an agreement between F5 and these
holders. A majority of these holders may generally require that we register the
common stock subject to these rights for public resale provided that the
proposed aggregate selling offering price would exceed $5.0 million. If we
register any of our common stock either for our own account or for the account
of other security holders, these holders may also include their common stock
subject to these rights in the registration, subject to the ability of the
underwriters to limit the number of shares included in the offering. The holders
of our common stock that was issued upon conversion of our Series B, C and D
preferred stock may also require us to register all or a portion of their common
stock subject to these rights on Form S-3, when use of this form becomes
available, provided that among other limitations, the proposed aggregate
offering price would be at least $2.0 million. The registration rights of a
holder terminates, when the holder can, within a three month period, offer and
sell all of his or her registrable securities pursuant to Rule 144 and as to all
holders, on June 4, 2002.

ANTI-TAKEOVER EFFECTS OF CERTAIN PROVISIONS OF AMENDED ARTICLES OF
  INCORPORATION, BYLAWS AND WASHINGTON LAW

    Our board of directors, without shareholder approval, has authority under
our amended articles of incorporation to issue preferred stock with rights
superior to the rights of the holders of common stock. As a result, our board
could issue preferred stock quickly and easily, which could adversely affect the
rights of holders of common stock and which our board could issue with terms
calculated to delay or prevent a change in control of F5 or make removal of
management more difficult.

    ELECTION AND REMOVAL OF DIRECTORS.  Our articles of incorporation provide
for the division of our board of directors into three classes, as nearly as
equal in number as possible, with the directors in each class serving for a
three-year term, and one class being elected each year by our shareholders. The
Class I term will expire at the annual meeting of shareholders to be held in
2000; the Class II term will expire at the annual meeting of shareholders to be
held in 2001; and the Class III term will expire at the annual meeting of
shareholders to be held in 2002. At each annual meeting of shareholders after
the initial classification, the successors to directors whose terms will then
expire will be elected to serve from the time of election and qualification
until the third annual meeting following election. Because this system of
electing and removing directors generally makes it more difficult for
shareholders to replace a majority of the board of directors, it may discourage
a third party from making a tender offer or otherwise attempting to gain control
of F5 and may maintain the incumbency of the board of directors.

    SHAREHOLDER MEETINGS.  Our bylaws provide that, except as otherwise required
by law or by our amended articles of incorporation, special meetings of the
shareholders can only be called pursuant to a resolution adopted by our board of
directors, the chairman of the board or president. These provisions of our
amended articles of incorporation and bylaws could discourage potential
acquisition proposals and could delay or prevent a change in control. These
provisions are intended to enhance the likelihood of continuity and stability in
the composition of the board of directors and in the policies formulated by the
board of directors and to discourage certain types of transactions that may
involve an actual or threatened change of control. These provisions are designed
to reduce our vulnerability to an unsolicited acquisition proposal. The
provisions also are intended to discourage certain tactics that may be used in
proxy fights. However, these provisions could have the effect of discouraging
others from making tender offers for our shares and, as a consequence, they also
may inhibit fluctuations in the market price of our shares that could result
from actual or rumored takeover attempts. Such provisions also may have the
effect of preventing changes in our management.

                                       51
<PAGE>
    Washington law also imposes restrictions on certain transactions between a
corporation and certain significant shareholders. Chapter 23B.19.040 of the
Washington Business Corporation Act prohibits a "target corporation," with
certain exceptions, from engaging in certain significant business transactions
with an "acquiring person," which is defined as a person or group of persons
that beneficially owns 10% or more of the voting securities of the target
corporation, for a period of five years after the acquisition, unless the
transaction or acquisition of shares is approved by a majority of the members of
the target corporation's board of directors prior to the time of acquisition.
Such prohibited transactions include, among other things:

    - a merger or consolidation with, disposition of assets to, or issuance or
      redemption of stock to or from, the acquiring person;

    - termination of 5% or more of the employees of the target corporation as a
      result of the acquiring person's acquisition of 10% or more of the shares;
      or

    - allowing the acquiring person to receive any disproportionate benefits as
      a shareholder.

    After the five-year period, a "significant business transaction" may occur,
as long as it complies with certain "fair price" provisions of the statute. A
corporation may not "opt out" of this statute. This provision may have the
effect of delaying, deferring or preventing a change in control.

TRANSFER AGENT

    The transfer agent and registrar for our common stock is American Stock
Transfer & Trust Company.

                                       52
<PAGE>
                        SHARES ELIGIBLE FOR FUTURE SALE

    Upon completion of this offering, we will have outstanding 18,626,667 shares
of common stock, assuming no exercise of options or warrants after August 31,
1999. Of these shares, 5,450,000 shares will be freely tradable without
restriction or further registration under the Securities Act; provided, however,
that if shares are owned by "affiliates," as that term is defined in Rule 144
under the Securities Act, their sales of shares would be subject to certain
limitations and restrictions that are described below.

    The remaining 13,176,667 shares of common stock, held by existing
shareholders as of August 31, 1999 were issued and sold by us in reliance on
exemptions from the registration requirements of the Securities Act. All of
these shares are subject to lock-up agreements described below. Upon expiration
of the lock-up agreements on December 2, 1999, substantially all of these shares
will become eligible for sale, subject in most cases to the limitations of Rules
144 and 701. In addition, holders of stock options and warrants could exercise
their options and warrants and sell the shares issued upon exercise as described
below.

    As of August 31, 1999, there were a total of 2,212,500 shares of common
stock that could be issued upon exercise of outstanding warrants. All of these
shares are subject to lock-up agreements. As of August 31, 1999, there were a
total of 1,579,640 shares of common stock subject to outstanding options under
our stock plans, of which 1,260,049 were vested. However, all of these shares
are subject to lock-up agreements. Shares purchased upon exercise of options
granted pursuant to our Amended and Restated 1996 Stock Option Plan, Amended and
Restated Directors' Nonqualified Stock Option Plan, 1998 Equity Incentive Plan,
1999 Non-Employees Directors' Plan and 1999 Employee Stock Purchase Plan
generally are available for resale in the public market.

    In connection with our initial public offering, the officers, directors and
then existing shareholders of F5 agreed not to sell or otherwise dispose of any
of their shares for a period ending December 2, 1999. Hambrecht & Quist,
however, may in its sole discretion, at any time and in most cases without
notice, release all or any portion of the shares subject to lock-up agreements.

RULE 144

    In general, under Rule 144 as currently in effect, a person who has
beneficially owned shares of F5's common stock for at least one year would be
entitled to sell, within any three-month period, a number of shares that does
not exceed the greater of:

    - 1% of the number of shares of common stock then outstanding, which will
      equal approximately 186,000 shares immediately after the effective date of
      this offering; or

    - the average weekly trading volume of the common stock on the Nasdaq
      National Market during the four calendar weeks preceding the filing of a
      notice on Form 144 with respect to this sale.

    Sales under Rule 144 are also subject to other requirements regarding the
manner of sale, notice filing and the availability of current public information
about F5.

RULE 701

    In general, under Rule 701, any F5 employee, director, officer, consultant
or advisor who purchases shares from F5 in connection with a compensatory stock
or option plan or other written agreement before the effective date of the
offering is entitled to resell these shares 90 days after the effective date of
this offering in reliance on Rule 144, without having to comply with certain
restrictions, including the holding period, contained in Rule 144.

    The SEC has indicated that Rule 701 will apply to typical stock options
granted by an issuer before it becomes subject to the reporting requirements of
the Securities Exchange Act of 1934, along with the

                                       53
<PAGE>
shares acquired upon exercise of these options (including exercises after the
date of this prospectus). Securities issued in reliance on Rule 701 are
restricted securities and, subject to the contractual restrictions described
above, beginning 90 days after the date of this prospectus, may be sold by
persons other than affiliates subject only to the manner of sale provisions of
Rule 144 and by affiliates under Rule 144 without compliance with its one year
minimum holding period requirement.

                                       54
<PAGE>
                                  UNDERWRITING

    Subject to the terms and conditions of the underwriting agreement, the
underwriters named below, through their representatives, Hambrecht & Quist LLC,
BancBoston Robertson Stephens Inc., Bear, Stearns & Co. Inc. and Dain Rauscher
Wessels, a division of Dain Rauscher Incorporated, have severally agreed to
purchase from F5 and the selling shareholders the following respective numbers
of shares of common stock.

<TABLE>
<CAPTION>
NAME                                                       NUMBER OF SHARES
- ---------------------------------------------------------  ----------------
<S>                                                        <C>
Hambrecht & Quist LLC....................................
BancBoston Robertson Stephens Inc........................
Bear, Stearns & Co. Inc..................................
Dain Rauscher Wessels, a division of Dain Rauscher
  Incorporated...........................................
                                                           ----------------
  Total..................................................      2,000,000
                                                           ----------------
                                                           ----------------
</TABLE>

    The underwriting agreement provides that the obligations of the underwriters
are subject to certain conditions precedent, including the absence of any
material adverse change in our business and the receipt of certain certificates,
opinions and letters from F5 and the selling shareholders, their counsel and the
independent auditors. The nature of the underwriters' obligation is such that
they have committed to purchase all shares of common stock offered hereby if any
of these shares are purchased.

    The underwriters are offering the shares of common stock directly to the
public at the public offering price set forth on the cover page of this
prospectus and to certain dealers at this price less a concession not in excess
of $  per share. The underwriters may allow and these dealers may re-allow a
concession not in excess of $  per share to certain other dealers. After the
public offering of the shares, the underwriters may change the offering price
and other selling terms.

    F5 and certain shareholders have granted to the underwriters an option,
exercisable no later than 30 days after the date of this prospectus, to purchase
up to 300,000 additional shares of common stock at the public offering price,
less the underwriting discount set forth on the cover page of this prospectus.
To the extent that the underwriters exercise this option, each of the
underwriters will have a firm commitment to purchase approximately the same
percentage thereof which the number of shares of common stock to be purchased by
it shown in the above table bears to the total number of shares of common stock
offered hereby. F5 and such shareholders will be obligated, pursuant to the
option, to sell shares to the underwriters to the extent the option is
exercised. The underwriters may exercise this option only to cover
over-allotments made in connection with the sale of shares of common stock
offered hereby. Kent L. Johnson, a director of the Company, is the president of
Alexander Hutton Capital, L.L.C., which is a member of the NASD. Mr. Johnson is
one of the shareholders who has granted the underwriters an option to purchase
additional shares in connection with their exercise of the over-allotment
option.

    The offering of the shares is made for delivery when, as and if accepted by
the underwriters and subject to prior sale and to withdrawal, cancellation or
modification of the offering without notice. The underwriters reserve the right
to reject an order for the purchase of shares in whole or in part.

    F5 and the selling shareholders have agreed to indemnify the underwriters
against certain liabilities, including liabilities under the Securities Act, and
to contribute to payments the underwriters may be required to make in respect
thereof.

    We have agreed that we will not, without the prior written consent of
Hambrecht & Quist LLC, offer, sell or otherwise dispose of any shares of common
stock, options or warrants to acquire shares of common stock or securities
exchangeable for or convertible into shares of common stock during the 90-day
period following the date of this prospectus, except that we may issue shares
upon the exercise of options granted prior to the date hereof, and may grant
additional options under our stock option plans.

                                       55
<PAGE>
    Certain persons participating in this offering may over-allot or effect
transactions that stabilize, maintain or otherwise affect the market price of
the common stock at levels above those that might otherwise prevail in the open
market, including by entering stabilizing bids, effecting syndicate covering
transactions or imposing penalty bids. A stabilizing bid means the placing of
any bid or effecting of any purchase, for the purpose of pegging, fixing or
maintaining the price of the common stock. A syndicate covering transaction
means the placing of any bid on behalf of the underwriting syndicate or the
effecting of any purchase to reduce a short position created in connection with
the offering. A penalty bid means an arrangement that permits the underwriters
to reclaim a selling concession from a syndicate member in connection with the
offering when shares of common stock sold by the syndicate member are purchased
in syndicate covering transactions. Such transactions may be effected on the
Nasdaq National Market, in the over-the-counter market, or otherwise. Such
stabilizing, if commenced may be discontinued at any time.

                                 LEGAL MATTERS

    The validity of the common stock offered hereby will be passed upon for F5
by Heller Ehrman White & McAuliffe, Seattle, Washington. Certain legal matters
will be passed upon for the underwriters by Gunderson Dettmer Stough Villeneuve
Franklin & Hachigian, LLP, Menlo Park, California.

                                    EXPERTS

    The financial statements as of September 30, 1997 and 1998 and June 30, 1999
and for the period from February 26, 1996, (inception), to September 30, 1996
and for each of the two years in the period ended September 30, 1998 and for the
nine months ended June 30, 1999 included in this prospectus have been so
included in reliance on the report of PricewaterhouseCoopers LLP, independent
accountants, given on the authority of said firm as experts in auditing and
accounting.

                           ADDITIONAL F5 INFORMATION

    We have filed with the SEC a registration statement on Form S-1 with respect
to the common stock offered hereby. This prospectus, which constitutes a part of
the registration statement, does not contain all of the information set forth in
the registration statement or the exhibits and schedules which are part of the
registration statement. For further information with respect to F5 and our
common stock, reference is made to the registration statement and the exhibits
and schedules thereto. You may read and copy any document we file at the SEC's
public reference rooms in Washington, D.C., New York, New York and Chicago,
Illinois. Please call the SEC at 1-800-SEC-0330 for further information about
the public reference rooms. Our SEC filings are also available to the public
from the SEC's Web site at
http://www.sec.gov. Information contained on F5's Web site does not constitute
part of this prospectus.

    We are subject to the information and periodic reporting requirements of the
Securities Exchange Act of 1934 and, in accordance therewith, file periodic
reports, proxy statements and other information with the SEC. Such periodic
reports, proxy statements and other information are available for inspection and
copying at the SEC's public reference rooms, our Web site and the Web site of
the SEC referred to above.

                                       56
<PAGE>
                               F5 NETWORKS, INC.
                         INDEX TO FINANCIAL STATEMENTS

<TABLE>
<CAPTION>
                                                                                                                PAGE
                                                                                                                -----
<S>                                                                                                          <C>
Report of Independent Accountants..........................................................................         F-2

Balance Sheets.............................................................................................         F-3

Statements of Operations...................................................................................         F-4

Statement of Shareholders' Equity (Deficit)................................................................         F-5

Statements of Cash Flows...................................................................................         F-6

Notes to Financial Statements..............................................................................         F-7
</TABLE>

                                      F-1
<PAGE>
                       REPORT OF INDEPENDENT ACCOUNTANTS

To the Board of Directors and Shareholders of
F5 Networks, Inc.

    In our opinion, the accompanying balance sheets and the related statements
of operations, of shareholders' equity (deficit) and of cash flows present
fairly, in all material respects, the financial position of F5 Networks, Inc. at
September 30, 1997 and 1998 and June 30, 1999, and the results of its operations
and its cash flows for the period from February 26, 1996 (inception) to
September 30, 1996 and for each of the years in the two year period ended
September 30, 1998 and for the nine months ended June 30, 1999, in conformity
with generally accepted accounting principles. These financial statements are
the responsibility of the Company's management; our responsibility is to express
an opinion on these financial statements based on our audits. We conducted our
audits of these statements in accordance with generally accepted auditing
standards which require that we plan and perform the audit to obtain reasonable
assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements, assessing the
accounting principles used and significant estimates made by management, and
evaluating the overall financial statement presentation. We believe that our
audits provide a reasonable basis for the opinion expressed above.

PricewaterhouseCoopers LLP

Seattle, Washington
September 2, 1999

                                      F-2
<PAGE>
                               F5 NETWORKS, INC.

                                 BALANCE SHEETS
                       (IN THOUSANDS, EXCEPT SHARE DATA)

<TABLE>
<CAPTION>
                                                                   SEPTEMBER 30,    SEPTEMBER 30,    JUNE 30,
                                                                       1997             1998           1999
                                                                  ---------------  ---------------  -----------
<S>                                                               <C>              <C>              <C>
                                                    ASSETS
Current assets:
  Cash and cash equivalents.....................................     $     143        $   6,206      $  26,948
  Accounts receivable, net of allowances of $0, $382 and $826...           329            2,032          5,858
  Inventories...................................................            77               99            710
  Other current assets..........................................            68              250            839
                                                                        ------           ------     -----------
        Total current assets....................................           617            8,587         34,355
Property and equipment, net.....................................           196              682          1,925
Software development costs, net of accumulated amortization of
  $4, $83 and $158..............................................            52              118             43
Other assets....................................................            54               45            163
                                                                        ------           ------     -----------
        Total assets............................................     $     919        $   9,432      $  36,486
                                                                        ------           ------     -----------
                                                                        ------           ------     -----------

                                LIABILITIES AND SHAREHOLDERS' EQUITY (DEFICIT)

Current liabilities:
  Accounts payable..............................................     $     117        $     559      $   3,540
  Accrued liabilities...........................................           114              458          1,579
  Deferred revenue..............................................           184              788          2,462
  Current portion of long-term debt.............................           500
  Capital lease obligations, current portion....................            19               19
                                                                        ------           ------     -----------
        Total current liabilities...............................           934            1,824          7,581
Capital lease obligations, net of current portion...............            19
Long-term debt, net of current portion..........................           197
                                                                        ------           ------     -----------
        Total liabilities.......................................         1,150            1,824          7,581
                                                                        ------           ------     -----------
Commitments (Note 9)
Redeemable convertible preferred stock, no par value:
  Series D Convertible, no, 1,138,438 and no shares issued and
    outstanding.................................................                          7,688
                                                                        ------           ------     -----------
Shareholders' equity (deficit):
  Preferred stock, no par value; 10,000,000 shares authorized
    Series A Convertible, 400,000, 400,000 and no shares issued
      and outstanding...........................................         1,123            1,123
    Series B Convertible, 156,250, 1,250,000 and no shares
      issued and outstanding....................................           208            1,656
    Series C Convertible, no, 156,250 and no shares issued and
      outstanding...............................................                          1,418
  Common stock, no par value; 100,000,000 shares authorized,
    6,000,000, 6,021,500 and 18,108,185 shares issued and
    outstanding.................................................           393            2,875         45,751
  Note receivable from shareholder..............................                                          (750)
  Unearned compensation.........................................          (169)          (1,694)        (3,960)
  Accumulated deficit...........................................        (1,786)          (5,458)       (12,136)
                                                                        ------           ------     -----------
      Total shareholders' equity (deficit)......................          (231)             (80)        28,905
                                                                        ------           ------     -----------
        Total liabilities and shareholders' equity..............     $     919        $   9,432      $  36,486
                                                                        ------           ------     -----------
                                                                        ------           ------     -----------
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-3
<PAGE>
                               F5 NETWORKS, INC.

                            STATEMENTS OF OPERATIONS
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
                                            PERIOD FROM
                                           FEBRUARY 26,
                                               1996        YEAR ENDED SEPTEMBER  NINE MONTHS ENDED JUNE
                                          (INCEPTION) TO           30,                    30,
                                           SEPTEMBER 30,   --------------------  ----------------------
                                               1996          1997       1998        1998        1999
                                          ---------------  ---------  ---------  -----------  ---------
                                                                                 (UNAUDITED)
<S>                                       <C>              <C>        <C>        <C>          <C>
Net revenues:
  Products..............................     $       2     $     229  $   4,119   $   2,537   $  11,872
  Services..............................            --            --        770         444       2,190
                                                ------     ---------  ---------  -----------  ---------
    Total net revenues..................             2           229      4,889       2,981      14,062
                                                ------     ---------  ---------  -----------  ---------

Cost of net revenues:
  Products..............................             1            71      1,091         694       3,085
  Services..............................            --            --        314         171         976
                                                ------     ---------  ---------  -----------  ---------
    Total cost of net revenues..........             1            71      1,405         865       4,061
                                                ------     ---------  ---------  -----------  ---------

  Gross profit..........................             1           158      3,484       2,116      10,001
                                                ------     ---------  ---------  -----------  ---------

Operating expenses:
  Sales and marketing...................            62           565      3,881       2,439       9,113
  Research and development..............           103           569      1,810       1,059       3,810
  General and administrative............           180           383      1,041         690       2,145
  Amortization of unearned
    compensation........................             4            69        420         205       1,797
                                                ------     ---------  ---------  -----------  ---------
    Total operating expenses............           349         1,586      7,152       4,393      16,865
                                                ------     ---------  ---------  -----------  ---------
Loss from operations....................          (348)       (1,428)    (3,668)     (2,277)     (6,864)
Other income (expense):
  Interest expense......................            --           (46)       (42)        (36)         (2)
  Interest income.......................            18            18         38          15         188
                                                ------     ---------  ---------  -----------  ---------
    Net loss............................     $    (330)    $  (1,456) $  (3,672)  $  (2,298)  $  (6,678)
                                                ------     ---------  ---------  -----------  ---------
                                                ------     ---------  ---------  -----------  ---------
Net loss per share--basic and diluted...     $   (0.06)    $   (0.24) $   (0.60)  $   (0.37)  $   (0.88)
                                                ------     ---------  ---------  -----------  ---------
                                                ------     ---------  ---------  -----------  ---------
Weighted average shares--basic and
  diluted...............................         5,932         6,000      6,086       6,135       7,582
                                                ------     ---------  ---------  -----------  ---------
                                                ------     ---------  ---------  -----------  ---------
Pro forma net loss per share
  (unaudited):
  Net loss per share--basic and
    diluted.............................                              $   (0.26)              $   (0.45)
                                                                      ---------               ---------
                                                                      ---------               ---------
  Weighted average shares--basic and
    diluted.............................                                 14,201                  14,923
                                                                      ---------               ---------
                                                                      ---------               ---------
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-4
<PAGE>
                               F5 NETWORKS, INC.
                  STATEMENT OF SHAREHOLDERS' EQUITY (DEFICIT)
       FOR THE PERIOD FROM FEBRUARY 26, 1996 (INCEPTION) TO JUNE 30, 1999
                       (IN THOUSANDS, EXCEPT SHARE DATA)
<TABLE>
<CAPTION>
                                   CONVERTIBLE PREFERRED STOCK AMOUNT
                                -----------------------------------------
                                 SHARES    SERIES A   SERIES B   SERIES C
                                ---------  --------   --------   --------
<S>                             <C>        <C>        <C>        <C>
Common stock issued to
  founding shareholders.......
Common stock issued for
  merger......................
Sales of Series A Convertible
  Preferred Stock,
  (net of issuance costs of
    $77)......................    370,000   $ 1,123
Issuance of Series A
  Convertible Preferred Stock
  upon payment of subscription
  receivable from
  shareholder.................     10,000
Unearned compensation.........
Amortization of unearned
  compensation................
Net loss......................
                                ---------  --------   --------   --------
Balance, September 30, 1996...    380,000     1,123
Issuance of Series A
  Convertible Preferred Stock
  upon payment of subscription
  receivable from
  shareholders................     20,000
Sales of Series B Convertible
  Preferred Stock.............    156,250              $   250
Value ascribed to warrants
  issued in conjunction with
  sale of Convertible
  Preferred Stock.............                             (42)
Value ascribed to warrants
  issued with note payable....
Unearned compensation.........
Amortization of unearned
  compensation................
Net loss......................
                                ---------  --------   --------   --------
Balance, September 30, 1997...    556,250     1,123        208
Sales of Series B Convertible
  Preferred Stock, (net of
  issuance costs of $30)......  1,093,750                1,740
Sales of Series C Convertible
  Preferred Stock, (net of
  issuance costs of $7).......    156,250                         $ 1,493
Value ascribed to warrants
  issued in conjunction with
  sales of Convertible
  Preferred Stock.............                            (292)       (75)
Exercise of stock options by
  employees...................
Exercise of stock warrants....
Repurchase of common stock
  under shareholder
  agreement...................
Issuance of common stock under
  shareholder agreement.......
Conversion of note payable to
  common stock................
Unearned compensation.........
Amortization of unearned
  compensation................
Net loss......................
                                ---------  --------   --------   --------
Balance, September 30, 1998...  1,806,250     1,123      1,656      1,418
Exercise of stock options by
  employees...................
Exercise of stock warrants....
Note receivable from
  shareholder for exercise of
  stock options ..............
Unearned compensation.........
Amortization of unearned
  compensation................
Conversion of convertible
  preferred stock to common
  stock in connection with the
  initial public offering.....  (1,806,250)   (1,123)   (1,656)    (1,418)
Issuance of common stock in an
  initial public offering (net
  of issuance costs of
  $3,051).....................
Net loss......................
                                ---------  --------   --------   --------
Balance, June 30, 1999........              $          $          $
                                ---------  --------   --------   --------
                                ---------  --------   --------   --------

<CAPTION>
                                                    SUBSCRIPTIONS
                                                       /NOTES
                                   COMMON STOCK      RECEIVABLE      UNEARNED
                                ------------------      FROM         COMPEN-     ACCUMULATED
                                  SHARES    AMOUNT  SHAREHOLDERS      SATION       DEFICIT      TOTAL
                                ----------  ------  -------------   ----------   -----------   -------
<S>                             <C>         <C>     <C>             <C>          <C>           <C>
Common stock issued to
  founding shareholders.......   5,388,000
Common stock issued for
  merger......................     612,000
Sales of Series A Convertible
  Preferred Stock,
  (net of issuance costs of
    $77)......................                          $(90)                                  $ 1,033
Issuance of Series A
  Convertible Preferred Stock
  upon payment of subscription
  receivable from
  shareholder.................                            30                                        30
Unearned compensation.........              $    4                   $    (4)
Amortization of unearned
  compensation................                                             4                         4
Net loss......................                                                     $  (330)       (330)
                                ----------  ------  -------------   ----------   -----------   -------
Balance, September 30, 1996...   6,000,000       4       (60)                         (330)        737
Issuance of Series A
  Convertible Preferred Stock
  upon payment of subscription
  receivable from
  shareholders................                            60                                        60
Sales of Series B Convertible
  Preferred Stock.............                                                                     250
Value ascribed to warrants
  issued in conjunction with
  sale of Convertible
  Preferred Stock.............                  42
Value ascribed to warrants
  issued with note payable....                 109                                                 109
Unearned compensation.........                 238                      (238)
Amortization of unearned
  compensation................                                            69                        69
Net loss......................                                                      (1,456)     (1,456)
                                ----------  ------  -------------   ----------   -----------   -------
Balance, September 30, 1997...   6,000,000     393                      (169)       (1,786)       (231)
Sales of Series B Convertible
  Preferred Stock, (net of
  issuance costs of $30)......                                                                   1,740
Sales of Series C Convertible
  Preferred Stock, (net of
  issuance costs of $7).......                                                                   1,493
Value ascribed to warrants
  issued in conjunction with
  sales of Convertible
  Preferred Stock.............                 367
Exercise of stock options by
  employees...................     215,750      29                                                  29
Exercise of stock warrants....       5,750       5                                                   5
Repurchase of common stock
  under shareholder
  agreement...................  (2,600,000)   (245)                                               (245)
Issuance of common stock under
  shareholder agreement.......   1,800,000     172                                                 172
Conversion of note payable to
  common stock................     600,000     209                                                 209
Unearned compensation.........               1,945                    (1,945)
Amortization of unearned
  compensation................                                           420                       420
Net loss......................                                                      (3,672)     (3,672)
                                ----------  ------  -------------   ----------   -----------   -------
Balance, September 30, 1998...   6,021,500   2,875                    (1,694)       (5,458)        (80)
Exercise of stock options by
  employees...................     534,809     209                                                 209
Exercise of stock warrants....     427,500     420                                                 420
Note receivable from
  shareholder for exercise of
  stock options ..............     150,000     750      (750)
Unearned compensation.........               4,063                    (4,063)
Amortization of unearned
  compensation................                                         1,797                     1,797
Conversion of convertible
  preferred stock to common
  stock in connection with the
  initial public offering.....   8,114,376  11,885                                               7,688
Issuance of common stock in an
  initial public offering (net
  of issuance costs of
  $3,051).....................   2,860,000  25,549                                              25,549
Net loss......................                                                      (6,678)     (6,678)
                                ----------  ------  -------------   ----------   -----------   -------
Balance, June 30, 1999........  18,108,185  $45,751     $(750)       $(3,960)      $(12,136)   $28,905
                                ----------  ------  -------------   ----------   -----------   -------
                                ----------  ------  -------------   ----------   -----------   -------
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-5
<PAGE>
                               F5 NETWORKS, INC.

                            STATEMENTS OF CASH FLOWS
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>
                                                          PERIOD FROM      YEAR ENDED SEPTEMBER  NINE MONTHS ENDED JUNE
                                                       FEBRUARY 26, 1996           30,                    30,
                                                        (INCEPTION) TO     --------------------  ----------------------
                                                      SEPTEMBER 30, 1996     1997       1998        1998        1999
                                                      -------------------  ---------  ---------  -----------  ---------
                                                                                                 (UNAUDITED)
<S>                                                   <C>                  <C>        <C>        <C>          <C>
Cash flows from operating activities:
  Net loss..........................................       $    (330)      $  (1,456) $  (3,672)  $  (2,298)  $  (6,678)
  Adjustments to reconcile net loss to net cash used
    in operating activities:
    Amortization of unearned compensation...........               4              69        420         205       1,797
    Provision for doubtful accounts and sales
      returns.......................................                                        605         399       1,078
    Depreciation and amortization...................              14              59        323         213         364
    Non cash interest expense.......................                               6         12          12
    Changes in operating assets and liabilities:
      Accounts receivable...........................              (1)           (328)    (2,308)     (1,108)     (4,904)
      Inventories...................................             (29)            (48)       (22)        (48)       (611)
      Other current assets..........................              (7)            (55)      (186)        (62)       (589)
      Other assets..................................              (6)            (48)         9          13        (119)
      Accounts payable and accrued liabilities......              37             194        806         762       4,100
      Deferred revenue..............................                             184        604         181       1,674
                                                              ------       ---------  ---------  -----------  ---------
        Net cash used in operating activities.......            (318)         (1,423)    (3,409)     (1,731)     (3,888)
                                                              ------       ---------  ---------  -----------  ---------
Cash flows from investing activities:
  Issuance of notes to officer......................                                        (10)        (10)
  Purchases of property and equipment...............            (150)            (98)      (731)       (425)     (1,531)
  Additions to software development costs...........                             (56)      (145)       (145)
  Proceeds from sale leaseback......................              30
                                                              ------       ---------  ---------  -----------  ---------
        Net cash used in investing activities.......            (120)           (154)      (886)       (580)     (1,531)
                                                              ------       ---------  ---------  -----------  ---------
Cash flows from financing activities:
  Proceeds from issuance of common stock in an
    initial public offering.........................                                                             25,549
  Proceeds from issuance of Series A Convertible
    Preferred Stock.................................           1,063              60
  Proceeds from issuance of Series B Convertible
    Preferred Stock.................................                             250      1,235       1,235
  Proceeds from issuance of Series C Convertible
    Preferred Stock.................................                                      1,493       1,493
  Proceeds from issuance of Series D Redeemable
    Convertible Preferred Stock.....................                                      7,688
  Proceeds from the exercise of stock options and
    warrants........................................                                         34          28         629
  Repurchase of common stock under shareholder
    agreement.......................................                                       (245)       (245)
  Proceeds from issuance of common stock under
    shareholder agreement...........................                                        172         172
  Proceeds from line of credit......................                                        825       1,075
  Repayments of line of credit......................                                       (825)       (825)
  Proceeds from issuance of long-term debt..........                             800
  Principal payments on capital lease obligations...              (1)            (14)       (19)        (16)        (17)
                                                              ------       ---------  ---------  -----------  ---------
        Net cash provided by financing activities...           1,062           1,096     10,358       2,917      26,161
                                                              ------       ---------  ---------  -----------  ---------
        Net increase (decrease) in cash and cash
          equivalents...............................             624            (481)     6,063         606      20,742
Cash and cash equivalents, at beginning of year.....              --             624        143         143       6,206
                                                              ------       ---------  ---------  -----------  ---------
Cash and cash equivalents, at end of year...........       $     624       $     143  $   6,206   $     749   $  26,948
                                                              ------       ---------  ---------  -----------  ---------
                                                              ------       ---------  ---------  -----------  ---------
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-6
<PAGE>
                               F5 NETWORKS, INC.

                         NOTES TO FINANCIAL STATEMENTS

1.  THE COMPANY AND BASIS OF PRESENTATION:

    F5 Networks, Inc. (formerly F5 Labs, Inc.) (the "Company") was incorporated
    on February 26, 1996 in the State of Washington.

    F5 is a leading provider of integrated Internet traffic management solutions
    designed to improve the availability and performance of mission-critical
    Internet-based servers and applications. The Company's proprietary
    software-based solutions monitor and manage local and geographically
    dispersed servers and intelligently direct traffic to the server best able
    to handle a user's request.

    The Company purchases material component parts and certain licensed software
    from suppliers and generally contracts with third parties for the assembly
    of products.

2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES:

    USE OF ESTIMATES

    The preparation of financial statements in conformity with generally
    accepted accounting principles requires management to make estimates and
    assumptions that affect the reported amounts of assets and liabilities and
    disclosures of contingent assets and liabilities as of the date of the
    financial statements and the reported amounts of expenses during the
    reporting period. Actual results could differ from those estimates.

    UNAUDITED INTERIM FINANCIAL STATEMENTS

    In the opinion of the Company's management, the June 30, 1998 unaudited
    interim financial statements include all adjustments, consisting of normal
    recurring adjustments, necessary for a fair presentation of the financial
    statements. All references hereinafter to June 30, 1998 amounts are based on
    unaudited information.

    CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS

    The Company considers all highly liquid investment securities with a
    maturity from the date of purchase of three months or less to be cash
    equivalents and investment securities with a weighted average maturity from
    the date of purchase of more than three months but less than one year to be
    short-term investments. As of June 30, 1999, the Company did not hold any
    short-term investments within its investment portfolio.

    CONCENTRATION OF CREDIT RISK

    The Company places its temporary cash investments with major financial
    institutions. As of June 30, 1999, all of the Company's temporary cash
    investments were placed with four institutions.

    The Company's customers are from diverse industries and geographic
    locations. Net revenues from international customers are denominated in U.S.
    Dollars and were approximately $0, $15,000 and $172,000 in the period from
    February 26, 1996 (inception) to September 30, 1996, and the years ended
    September 30, 1997 and 1998, respectively and $172,000 and $1.0 million for
    the nine months ended June 30, 1998 and 1999. For the nine months ended June
    30, 1999, one customer accounted for 21.7% of net revenues. During the
    period from February 26, 1996 (inception) to September 30, 1996, the years
    ended September 30, 1997 and 1998, and the nine months ended June 30, 1998,
    no single customer accounted for more than 10% of the Company's net
    revenues. At June 30, 1999, one

                                      F-7
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: (CONTINUED)
    customer represented 29.4% of accounts receivable. At September 30, 1997 and
    1998, there were no significant accounts receivable from a single customer.
    The Company does not require collateral to support credit sales. Allowances
    are maintained for potential credit losses and sales returns.

    INVENTORIES

    Inventories consist of hardware, software and related component parts and
    are recorded at the lower of cost or market (as determined by the first-in,
    first-out method).

    PROPERTY AND EQUIPMENT

    Property and equipment is stated at cost. Equipment under capital leases is
    stated at the lower of the present value of the minimum lease payments
    discounted at the Company's incremental borrowing rate at the beginning of
    the lease term or fair value at the inception of the lease. Depreciation of
    property and equipment and amortization of capital leases are provided on
    the straight-line method over the estimated useful lives of the assets of 2
    to 5 years. Leasehold improvements are amortized over the lesser of the term
    of the lease or the estimated useful life of the improvements.

    The cost of normal maintenance and repairs is charged to expense as incurred
    and expenditures for major improvements are capitalized at cost. Gains or
    losses on the disposition of assets in the normal course of business are
    reflected in the results of operations at the time of disposal.

    SOFTWARE DEVELOPMENT COSTS

    Software development costs incurred in conjunction with product development
    are charged to research and development expense until technological
    feasibility is established. Thereafter, until the product is released for
    sale, software development costs are capitalized and reported at the lower
    of unamortized cost or net realizable value of each product. The
    establishment of technological feasibility and the on-going assessment of
    recoverability of costs require considerable judgment by the Company with
    respect to certain internal and external factors, including, but not limited
    to, anticipated future gross product revenues, estimated economic life and
    changes in hardware and software technology. The Company amortizes
    capitalized software costs using the straight-line method over the estimated
    economic life of the product, generally two years.

    VALUATION OF LONG-LIVED ASSETS

    The Company periodically evaluates the carrying value of long-lived assets
    to be held and used, including, but not limited to, property and equipment
    and other assets, when events and circumstances warrant such a review. The
    carrying value of a long-lived asset is considered impaired when the
    anticipated undiscounted cash flow from the asset is separately identifiable
    and is less than its carrying value. In that event, a loss is recognized
    based on the amount by which the carrying value exceeds the fair value of
    the long-lived asset. Fair value is determined primarily using the
    anticipated cash flows discounted at a rate commensurate with the risk
    involved. Losses on long-lived assets to be disposed of are determined in a
    similar manner, except that fair values are reduced for the cost to dispose.

                                      F-8
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: (CONTINUED)
    REVENUE RECOGNITION

    The Company recognizes software revenue under Statement of Position 97-2,
    "Software Revenue Recognition," and SOP 98-9 "Modification of SOP 97-2,
    Software Revenue Recognition, with Respect to Certain Transactions."

    The Company sells products through resellers, original equipment
    manufacturers and other channel partners, as well as to end users, under
    similar terms. The Company generally combines software license, installation
    and customer support elements into a package with a single "bundled" price.
    The Company allocates a portion of the sales price to each element of the
    bundled package based on their respective fair values when the individual
    elements are sold separately. Revenues from the license of software, net of
    an allowance for estimated returns, are recognized when the product has been
    shipped and the customer is obligated to pay for the product. Installation
    revenue is recognized when the product has been installed at the customer's
    site. Revenues for customer support are recognized on a straight-line basis
    over the service contract terms. Estimated sales returns are based on
    historical experience by product and are recorded at the time revenues are
    recognized.

    ADVERTISING

    Advertising costs are expensed as incurred. Advertising expense was $0, $0
    and $256,000 for the period from February 26, 1996 (inception) to September
    30, 1996 and the years ended September 30, 1997 and 1998, respectively, and
    $142,000 and $794,000, for the nine months ended June 30, 1998 and 1999,
    respectively.

    INCOME TAXES

    The Company accounts for income taxes under the liability method of
    accounting. Under the liability method, deferred taxes are determined based
    on the differences between the financial statement and tax bases of assets
    and liabilities at enacted tax rates in effect in the year in which the
    differences are expected to reverse. Valuation allowances are established,
    when necessary, to reduce deferred tax assets to amounts expected to be
    realized.

    STOCK-BASED COMPENSATION

    The Company accounts for stock-based employee compensation arrangements in
    accordance with the provisions of Accounting Principles Board Opinion No. 25
    ("APB No. 25"), "Accounting for Stock Issued to Employees" and complies with
    the disclosure provisions of Statement of Financial Accounting Standards No.
    123 ("SFAS No. 123"), "Accounting for Stock-Based Compensation." Under APB
    No. 25, compensation expense is based on the difference, if any, on the date
    of the grant, between the deemed fair value of the Company's stock and the
    exercise price of the option. The unearned compensation is being amortized
    in accordance with Financial Accounting Standards Board Interpretation No.
    28 on an accelerated basis over the vesting period of the individual
    options. The Company accounts for equity instruments issued to nonemployees
    in accordance with the provisions of SFAS No. 123.

                                      F-9
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: (CONTINUED)
    FAIR VALUE OF FINANCIAL INSTRUMENTS

    For certain financial instruments, including cash and cash equivalents,
    accounts receivable, accounts payable and accrued liabilities, recorded
    amounts approximate market value.

    NET LOSS PER SHARE

    Effective October 1, 1997, the Company adopted Statement of Financial
    Accounting Standards No. 128 ("SFAS No. 128"), "Earnings per Share." SFAS
    No. 128 requires the presentation of basic and diluted earnings (loss) per
    share for all periods presented.

    In accordance with SFAS No. 128, basic net loss per share has been computed
    using the weighted-average number of shares of common stock outstanding
    during the period, except that pursuant to Securities and Exchange
    Commission Staff Accounting Bulletin No. 98, if applicable, common shares
    issued in each of the periods presented for nominal consideration have been
    included in the calculation as if they were outstanding for all periods
    presented. Pro forma basic and diluted net loss per share have been computed
    as described above and also include the weighted average convertible
    preferred stock outstanding as if those shares were converted to common
    stock at the time of issuance.

    Dilutive securities include options, warrants and preferred stock on an as
    if converted basis. Potentially dilutive securities totaling 3,636,000 for
    the period from February 26, 1996 (inception) to September 30, 1996 and
    5,066,000 and 12,819,126 for the years ended September 30, 1997 and 1998,
    respectively, and 10,582,126 and 4,581,762 for the nine months ended June
    30, 1998 (unaudited) and 1999, respectively, were excluded from historical
    basic and diluted loss per share because of their anti-dilutive effect.

    NEW ACCOUNTING PRONOUNCEMENTS

    In June 1997, the Financial Accounting Standards Board (the "FASB") issued
    Statement of Financial Accounting Standards No. 130, "Reporting
    Comprehensive Income." This statement requires that changes in comprehensive
    income be shown in a financial statement that is displayed with the same
    prominence as other financial statements. The statement is effective for
    fiscal years beginning after December 15, 1997. Reclassification for earlier
    periods is required for comparative purposes. The Company does not have any
    material items of comprehensive income, other than net loss, and
    accordingly, the statement does not have any material impact on reported
    financial position or results of operations.

    In June 1997, the FASB issued Statement of Financial Accounting Standards
    No. 131, "Disclosures About Segments of an Enterprise and Related
    Information." This statement supersedes Statement of Financial Accounting
    Standards No. 14, "Financial Reporting for Segments of a Business
    Enterprise." This statement includes requirements to report selected segment
    information quarterly and entity-wide disclosures about products and
    services, major customers, and geographic areas in which the entity holds
    significant assets and reports significant revenues. The statement is
    effective for fiscal year 1999. The Company operates in one segment
    providing integrated Internet traffic management solutions.

    In June 1998, the FASB issued Statement of Financial Accounting Standards
    No. 133, "Accounting for Derivative Instruments and Hedging Activities."
    This statement requires that all derivative

                                      F-10
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: (CONTINUED)
    instruments be recorded on the balance sheet at their fair value. Changes in
    the fair value of derivatives are recorded each period in current earnings
    or other comprehensive income, depending on whether a derivative is
    designated as part of a hedge transaction and, if it is, the type of hedge
    transaction. In July 1999, the FASB issued SFAS No. 137, "Accounting for
    Derivative Instruments and Hedging Activities--Deferral of the Effective
    Date of FASB Statement No. 133." SFAS No. 137 deferred the effective date of
    SFAS No. 133 until fiscal years beginning after June 15, 2000. The Company
    does not use derivative instruments, therefore the adoption of this
    statement will not have any effect on the Company's results of operations or
    its financial position.

    In March 1998, the American Institute of Certified Public Accountants issued
    Statement of Position 98-1, "Accounting for the Costs of Computer Software
    Developed or Obtained for Internal Use," which establishes guidelines for
    the accounting for the costs of all computer software developed or obtained
    for internal use. This statement is effective for fiscal years beginning
    after December 15, 1998. The Company does not expect the statement to have a
    material impact on its financial statements.

3.  PROPERTY AND EQUIPMENT:

    At September 30, 1997 and 1998 and June 30, 1999, property and equipment
    consist of the following:

<TABLE>
<CAPTION>
                                                                             SEPTEMBER 30,
                                                                          --------------------   JUNE 30,
                                                                            1997       1998        1999
                                                                             ---     ---------  -----------
                                                                                   (IN THOUSANDS)
<S>                                                                       <C>        <C>        <C>
Computer equipment......................................................  $     161  $     529   $   1,128
Equipment under capital leases..........................................         54         54          54
Office furniture and equipment..........................................         17        293         574
Leasehold improvements..................................................         29        116         330
Work in process.........................................................                               437
                                                                                ---  ---------  -----------
                                                                                261        992       2,523
Accumulated amortization for equipment under
  capital leases........................................................        (15)       (33)        (46)
Accumulated depreciation................................................        (50)      (277)       (552)
                                                                                ---  ---------  -----------
                                                                          $     196  $     682   $   1,925
                                                                                ---  ---------  -----------
                                                                                ---  ---------  -----------
</TABLE>

    Depreciation expense was approximately $14,000 for the period from February
    26, 1996 (inception) to September 30, 1996 and $55,000 and $244,000 for the
    years ended September 30, 1997 and 1998, respectively. Depreciation expense
    was approximately $161,000 and $289,000 for the nine months ended June 30,
    1998 (unaudited) and 1999, respectively.

                                      F-11
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

4.  ACCRUED LIABILITIES:

    At September 30, 1997 and 1998 and June 30, 1999, accrued liabilities
    consist of the following:

<TABLE>
<CAPTION>
                                                                               SEPTEMBER 30,
                                                                            --------------------   JUNE 30,
                                                                              1997       1998        1999
                                                                               ---        ---     -----------
                                                                                     (IN THOUSANDS)
<S>                                                                         <C>        <C>        <C>
Accrued payroll and benefits..............................................  $      37  $     237   $     871
Accrued sales and use taxes...............................................         17        141         287
Other.....................................................................         60         80         421
                                                                                  ---        ---  -----------
                                                                            $     114  $     458   $   1,579
                                                                                  ---        ---  -----------
                                                                                  ---        ---  -----------
</TABLE>

5.  INCOME TAXES:

    The provisions for federal income tax differs from the amount computed by
    applying the statutory federal income tax rate for the following reasons:

<TABLE>
<CAPTION>
                                                               SEPTEMBER 30,
                                                           ----------------------    JUNE 30,
                                                              1997        1998         1999
                                                           ----------  ----------  ------------
<S>                                                        <C>         <C>         <C>
Federal income tax benefit at statutory rate.............        (34)%       (34)%        (34)%
Non-deductible stock compensation........................          1%          3%           7%
Other....................................................                      1            1
                                                                 ---         ---          ---
Change in valuation allowance............................         33%         30%          26%
                                                                 ---         ---          ---
                                                                 ---         ---          ---
</TABLE>

    Deferred tax assets and liabilities at September 30, 1997 and 1998 and June
    30, 1999 consist of the following:

<TABLE>
<CAPTION>
                                                             SEPTEMBER 30,
                                                          --------------------   JUNE 30,
                                                            1997       1998        1999
                                                          ---------  ---------  -----------
<S>                                                       <C>        <C>        <C>
Deferred tax assets:
  Net operating loss carryforwards......................  $     583  $   1,573   $   3,000
  Allowance for doubtful accounts.......................                    80         281
  Accrued compensation and benefits.....................          8         61         116
  Depreciation..........................................                     9          19
                                                          ---------  ---------  -----------
    Total deferred tax assets...........................        591      1,723       3,416
                                                          ---------  ---------  -----------
Deferred tax liabilities:
  Depreciation..........................................         (7)
  Amortization..........................................        (14)       (53)        (13)
                                                          ---------  ---------  -----------
    Total deferred tax liabilities......................        (21)       (53)        (13)
                                                          ---------  ---------  -----------
                                                                570      1,670       3,403
Valuation allowance.....................................       (570)    (1,670)     (3,403)
                                                          ---------  ---------  -----------
                                                          $       0  $       0   $       0
                                                          ---------  ---------  -----------
                                                          ---------  ---------  -----------
</TABLE>

                                      F-12
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

5.  INCOME TAXES: (CONTINUED)
    Differences between the tax bases of assets and liabilities and their
    financial statement amounts are reflected as deferred income taxes based on
    enacted tax rates. The net deferred tax assets have been reduced by a full
    valuation allowance at September 30, 1997 and 1998 and June 30, 1999 based
    on management's determination that the recognition criteria for realization
    have not been met.

    As of June 30, 1999, the Company had net operating loss carryforwards of
    approximately $8.8 million, to offset future taxable income for Federal
    income tax purposes, which will expire between 2011 and 2019. Should certain
    changes in the Company's ownership occur, there could be a limitation on the
    utilization of its net operating losses.

6.  LINES OF CREDIT:

    In July 1998, the Company entered into a line of credit which allows the
    Company to borrow up to the lesser of $2.0 million or 75% of the Company's
    eligible accounts receivable. The terms of the agreement call for monthly
    interest payments, interest at the prime rate plus 0.5% and a due date of
    August 31, 1999. This line of credit was not renewed upon expiration. The
    line of credit contains certain covenants, including, but not limited to,
    meeting minimum financial ratios and earnings. No amount was outstanding
    under the line of credit at June 30, 1999.

7.  LONG-TERM DEBT:

    In March and August 1997, the Company entered into $500,000 and $300,000
    convertible note agreements with a preferred shareholder, respectively.
    These notes bore simple interest at 11% annually, matured 18 months from the
    date of the respective agreements and were collateralized by substantially
    all of the Company's assets. In October 1997, the Company settled the
    $500,000 note and related accrued interest by issuing to the preferred
    shareholder 312,500 shares of the Company's Series B Convertible Preferred
    Stock. In November 1997, the preferred shareholder converted the $300,000
    note and related accrued interest into 600,000 shares of the Company's
    common stock. In conjunction with these notes, the Company issued to the
    preferred shareholder warrants to purchase 100,000 and 600,000 shares of the
    Company's common stock at $0.64 and $0.50 per share, respectively. The
    aggregate value assigned to the warrants issued with these notes payable of
    $0 and $109,000, respectively, was reflected as both a debt discount and an
    increase to common stock. The debt discount was accounted for as a component
    of interest expense using a method which approximated the interest method.

8.  SHAREHOLDERS' EQUITY:

    A.  PREFERRED STOCK

    In connection with the Company's initial public offering (note 8c), all
    outstanding shares of the Company's Convertible Preferred Stock and
    Redeemable Convertible Preferred Stock were converted into an aggregate of
    8,114,376 shares of the Company's common stock.

    The Series A Convertible Preferred Stock is non-cumulative and convertible
    into six shares of common stock, subject to adjustment upon the occurrence
    of certain events provided for in the Company's restated articles of
    incorporation. The Series A Convertible Preferred Stock is mandatorily
    convertible into common stock upon completion of an initial public offering
    of the Company's common stock in which the price per share equals or exceeds
    $1.50 and gross proceeds equal or

                                      F-13
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    exceed $12.0 million, or when two-thirds of the shares of Series A
    Convertible Preferred Stock have been converted. The holders of the Series A
    Convertible Preferred Stock have certain voting rights and liquidation
    preferences equal to $3.00 per share.

    In May 1996, the Company issued 370,000 shares of Series A Convertible
    Preferred Stock for an aggregate purchase price of $1.1 million. In
    conjunction with the issuance of the Company's Series A shares to a certain
    investor, the Company issued warrants, to which no value was assigned, to
    purchase 240,000 shares of the Company's common stock at $0.50 per share. On
    December 30, 1998, these warrants were exercised.

    In addition, the Company entered into stock subscriptions for 30,000 shares
    of the Company's Series A Convertible Preferred Stock in exchange for notes
    receivable from certain investors for an aggregate of $90,000. These notes
    receivable bore interest at 9% per annum and had maturity periods ranging
    from 3 to 6 months from the date of the agreements. In August 1996, 10,000
    shares of the Company's Series A Convertible Preferred Stock were issued
    upon payment in full of $30,000 principal value and accrued interest of a
    subscription agreement. In fiscal year 1997, the Company issued the
    remaining 20,000 shares under subscription upon payment in full of the
    remaining principal amount and accrued interest.

    In September 1997, the Company issued 156,250 shares of Series B Convertible
    Preferred Stock for an aggregate purchase price of $250,000. In conjunction
    with this issuance, the Company issued warrants to purchase 187,500 shares
    of the Company's common stock at $0.80 per share. The Company has allocated
    approximately $42,000 of the purchase price as the value of these warrants.
    The Series B Convertible Preferred Stock is non-cumulative and convertible
    into two shares of the Company's common stock, subject to adjustment upon
    the occurrence of certain events provided for in the Company's amended and
    restated articles of incorporation. The Series B Convertible Preferred Stock
    is mandatorily convertible into common stock upon completion of an initial
    public offering of the Company's common stock in which the price per share
    equals or exceeds $3.20 and gross proceeds equal or exceed $8.0 million, or
    when two-thirds of the Series B shares have been converted. The holders of
    the Series B Convertible Preferred Stock have certain voting rights and
    liquidation preferences equal to $1.60 per share.

    In October and November 1997, the Company issued an additional 1,093,750
    shares of the Company's Series B Convertible Preferred Stock for an
    additional aggregate purchase price of $1.8 million, including conversion of
    the $500,000 note and accrued interest of approximately $20,000 from a
    preferred shareholder (see Note 7). In conjunction with this issuance, the
    Company issued warrants to purchase 1,312,500 shares of the Company's common
    stock at $0.80 per share. The Company has allocated approximately $292,000
    of the purchase price of the Series B Convertible Preferred Stock as the
    value of these warrants.

    In April 1998, the Company issued 156,250 shares of the Company's Series C
    Convertible Preferred Stock and warrants to purchase 187,500 shares of the
    Company's common stock at $1.60 per share for an aggregate purchase price of
    $1.5 million. The Company has allocated approximately $75,000 of the
    purchase price of the Series C Convertible Preferred Stock as the value of
    the warrants issued. On February 1, 1999 these warrants were exercised.
    Shares of the Company's Series C Convertible Preferred Stock are
    non-cumulative and convertible into six shares of the Company's common
    stock, subject to the occurrence of certain events provided for in the
    Company's amended and restated articles of incorporation. The shares are
    mandatorily convertible upon the completion of an initial

                                      F-14
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    public offering in which the per share price is equal to or exceeds $3.20
    and gross proceeds equal or exceed $8.0 million, or when two-thirds of the
    Series C Convertible Preferred shares have been converted. The holders of
    the Series C Convertible Preferred Stock have certain voting rights and
    liquidation preferences equal to $9.60 per share.

    In August 1998, the Company issued 1,138,438 shares of Series D Redeemable
    Convertible Preferred Stock for an aggregate purchase price of approximately
    $7.7 million. Holders of the Company's Series D Redeemable Convertible
    Preferred Stock are entitled to receive an annual non-cumulative dividend of
    $0.68 per share, subject to declaration by the Board of Directors, at their
    sole discretion. The shares are convertible into two shares of the Company's
    Common Stock, subject to the occurrence of certain events provided for in
    the Company's amended and restated articles of incorporation. The shares are
    mandatorily convertible into common stock upon the completion of an initial
    public offering in which the per share price equals or exceeds $5.00 and
    gross proceeds are equal to or exceed $15.0 million. The Company is required
    to redeem all outstanding shares of the Series D Redeemable Convertible
    Preferred Stock at $6.79 per share, plus all declared and unpaid dividends,
    either in August 2005 or in three annual installments beginning August 2003
    at the request of holders of at least two-thirds of the outstanding Series D
    Redeemable Convertible Preferred Stock. The holders of the Series D
    Redeemable Convertible Preferred Stock have certain voting rights and
    liquidation preferences equal to $13.58 per share.

    B.  COMMON STOCK

    The Company issued 5,388,000 shares of common stock on February 26, 1996,
    the date of its incorporation. In conjunction with the Company's formation
    it entered into a merger with Ambiente Inc. ("Ambiente") which was
    consummated in March 1996. Pursuant to the merger agreement, the Company
    issued 612,000 shares of common stock to the shareholders of Ambiente.
    Through the date of the merger, Ambiente had no significant operations,
    assets or liabilities, other than software under development that had not
    yet achieved technological feasibility. Accordingly, no value was assigned
    to the stock issued.

    On December 2, 1996 and January 27, 1999 the Company authorized a 3 for 1
    and 2 for 1 stock split, in the form of stock dividends, respectively on the
    Company's common stock. All references to number of shares and per share
    amounts of the Company's common stock in the accompanying financial
    statements and notes have been restated to reflect these stock splits.

    Upon incorporation of the Company, the founding shareholders entered into an
    agreement (as amended, the "Shareholder Agreement") which, among other
    things, called for a mandatory offer to sell the shareholders' stock, first
    to the remaining founders, then to the Company, in the event of termination
    of their employment with the Company. In February 1998, one of the founders,
    who was also an officer of the Company, and the Company purchased 2,600,000
    shares of the Company's common stock under the Shareholder Agreement from
    two founders who had terminated their employment. The Company facilitated
    the transactions between the shareholders under the Shareholder Agreement,
    retaining 800,000 of the repurchased shares.

    In February 1999, the Company issued a warrant to purchase up to 12,500
    shares of the Company's common stock at $8.00 per share to a certain
    customer in conjunction with a sale of products.

                                      F-15
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    C.  INITIAL PUBLIC OFFERING

    On June 4, 1999, the Company issued 2,860,000 shares of its common stock at
    an initial public offering price of $10.00 per share. Also sold in this
    offering were 590,000 shares held by selling shareholders, including 450,000
    shares sold upon the exercise of the underwriters' overallotment option. The
    net proceeds to the Company from the offering, net of offering costs of
    approximately $3.1 million were approximately $25.5 million. Concurrent with
    the initial public offering, each outstanding share of the Company's
    convertible preferred stock was automatically converted into common stock.

    The Company has issued warrants to purchase common stock to investors and to
    a certain customer. The aggregate consideration for each respective
    transaction was allocated to securities or debt and the warrants based on
    their relative fair values. All the warrants were exercisable at the time of
    issuance. The assumptions applied in the determination of the fair value of
    warrants issued were (i) use of the Black-Scholes pricing model, (ii) risk
    free interest rates ranging from 5.2% to 6.2%, (iii) expected volatility
    rates of approximately 70% (based on disclosed expected volatility rates of
    comparable companies) and actual volatility subsequent to the initial public
    offering, (iv) assumed expected lives of 4 to 10 years, and (v) no expected
    dividends.

    At June 30, 1999, warrants outstanding were as follows:

<TABLE>
<CAPTION>
                                                                                                AGGREGATE
WARRANT TO                                                          SHARES OF      EXERCISE      EXERCISE
PURCHASE                                                           COMMON STOCK      PRICE        PRICE
- ----------------------------------------------------------------  --------------  -----------  ------------
<S>                                                               <C>             <C>          <C>
Common stock....................................................        100,000    $    0.64   $     64,000
Common stock....................................................        600,000         0.50        300,000
Common stock....................................................      1,500,000         0.80      1,200,000
Common stock....................................................         12,500         8.00        100,000
                                                                  --------------               ------------
                                                                      2,212,500                $  1,664,000
                                                                  --------------               ------------
                                                                  --------------               ------------
</TABLE>

    D.  EQUITY INCENTIVE PLANS

    In January 1997, Company's shareholders approved the Amended and Restated
    1996 Stock Option Plan (the "1996 Employee Plan") that provides for
    discretionary grants of non-qualified and incentive stock options for
    employees and other service providers, and the Amended and Restated
    Directors' Nonqualified Stock Option Plan (the "1996 Directors' Plan"),
    which provides for automatic grants of non-qualified stock options to
    eligible non-employee directors. A total of 2,600,000 shares of common stock
    has been reserved for issuance under the 1996 Employee Plan and the 1996
    Directors' Plan. Employees' stock options typically vest over a period of
    four years from the grant date; director options typically vest over a
    period of three years from the grant date. All options under the 1996
    Employee Plan and the 1996 Directors' Plan expire 10 years after the grant
    date. In August 1997, the Company repriced all existing employee options to
    an exercise price of $0.05 per share. This repricing was accounted for as a
    cancellation of existing stock options and grant of new stock options. All
    outstanding, unvested options under the 1996 Employee Plan and the 1996
    Director's Plan vest in full upon a change in control of the Company. The
    Company does not intend to grant any additional options under either of
    these Plans.

                                      F-16
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    In November 1998, the Company's shareholders adopted the 1998 Equity
    Incentive Plan (the "1998 Plan"), which provides for discretionary grants of
    non-qualified and incentive stock options, stock purchase awards and stock
    bonuses for employees and other service providers. A total of 800,000 shares
    of common stock have been reserved for issuance under the 1998 Plan. Stock
    options granted under this plan typically vest over a period of four years
    from the grant date, and expire 10 years from the grant date. The Company
    has not granted any stock purchase awards or stock bonuses under the 1998
    Plan. Upon certain changes in control of the Company, the surviving entity
    will either assume or substitute all outstanding options or stock awards
    under the 1998 Plan. If the surviving entity determines not to assume or
    substitute such options or awards, then with respect to persons whose
    service with the Company or an affiliate of the Company has not terminated
    before a change in control, the vesting of 50% of these options or stock
    awards (and the time during which these awards may be exercised) will
    accelerate and the options or awards terminated if not exercised before the
    change in control.

    The Company applies the accounting provisions prescribed in APB No. 25 and
    related interpretations. In certain instances, the Company has issued stock
    options with an exercise price less than the deemed fair value of the
    Company's common stock at the date of grant. Accordingly, total compensation
    costs related to these stock options of approximately $238,000 and $1.9
    million was deferred during fiscal years 1997 and 1998, respectively, and
    $1.1 million and $4.1 million for the nine months ended June 30, 1998
    (unaudited) and 1999, respectively, and is being amortized over the vesting
    period of the options, generally four years. Amortization of unearned
    compensation costs of approximately $4,000 has been recognized as an expense
    for the period from February 26, 1996 (inception) to September 30, 1996,
    $69,000 and $420,000 for the years ended September 30, 1997 and 1998,
    respectively. Amortization of unearned compensation amounted to $205,000 and
    $1.8 million for the nine months ended June 30, 1998 (unaudited) and 1999,
    respectively.

                                      F-17
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    A summary of stock option transactions are as follows:

<TABLE>
<CAPTION>
                                                                                             WEIGHTED
                                                                                              AVERAGE
                                                                             OUTSTANDING  EXERCISE PRICE
                                                                               OPTIONS       PER SHARE
                                                                             -----------  ---------------
<S>                                                                          <C>          <C>
Inception
Options granted............................................................    1,146,000     $    0.38
Options canceled...........................................................     (150,000)         0.34
                                                                             -----------
Balances at September 30, 1996.............................................      996,000          0.38

Options granted............................................................    1,349,000          0.15
Options canceled...........................................................   (1,119,000)         0.36
                                                                             -----------
Balances at September 30, 1997.............................................    1,226,000          0.15

Options granted............................................................    1,543,000          0.29
Options exercised..........................................................     (215,750)         0.11
Options canceled...........................................................     (476,000)         0.11
                                                                             -----------
Balances at September 30, 1998.............................................    2,077,250          0.26

Options granted............................................................    1,171,121          3.53
Options exercised..........................................................     (684,809)         1.36
Options canceled...........................................................     (194,300)         1.09
                                                                             -----------
Balances at June 30, 1999..................................................    2,369,262          1.50
                                                                             -----------
                                                                             -----------
</TABLE>

    Pro forma information regarding net loss is required by SFAS No. 123, and
    has been determined as if the Company had accounted for its stock options
    under the minimum value method of that statement. The fair value of each
    option is estimated at the date of grant with the following weighted-average
    assumptions used for grants issued for the period from February 26, 1996
    (inception) to September 30, 1996, for the years ended September 30, 1997
    and 1998, and for the nine months ended June 30, 1999:

<TABLE>
<CAPTION>
                                                         PERIOD FROM
                                                        FEBRUARY 26,
                                                            1996       YEAR ENDED SEPTEMBER  NINE MONTHS
                                                         (INCEPTION)           30,              ENDED
                                                        TO SEPTEMBER   --------------------    JUNE 30,
                                                          30, 1996       1997       1998         1999
                                                        -------------  ---------  ---------  ------------
<S>                                                     <C>            <C>        <C>        <C>
Risk-free interest rate...............................        6.21%        6.21%      4.62%        5.47%

Dividend yield........................................        0.00%        0.00%      0.00%        0.00%

Expected term of option...............................      4 years      4 years    4 years      4 years

Volatility subsequent to initial public offering......                                            69.87%
</TABLE>

                                      F-18
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    For purposes of pro forma disclosures, the estimated fair value of the
    options is amortized over the options' vesting period. The Company's net
    loss would have been as indicated in the pro forma table below:

<TABLE>
<CAPTION>
                                                   PERIOD FROM
                                                  FEBRUARY 26,
                                                      1996        YEAR ENDED SEPTEMBER
                                                 (INCEPTION) TO           30,            NINE MONTHS ENDED
                                                  SEPTEMBER 30,   --------------------       JUNE 30,
                                                      1996          1997       1998            1999
                                                 ---------------  ---------  ---------  -------------------
                                                         (IN THOUSANDS, EXCEPT
                                                            PER SHARE DATA)
<S>                                              <C>              <C>        <C>        <C>
Net loss--as reported..........................     $    (330)    $  (1,456) $  (3,672)      $  (6,678)

Net loss--pro forma............................          (331)       (1,468)    (3,742)         (7,057)

Net loss per share--as reported................         (0.06)        (0.24)     (0.60)          (0.88)

Net loss per share--pro forma..................         (0.06)        (0.24)     (0.61)          (0.93)
</TABLE>

    The weighted-average fair values and weighted-average exercise prices per
    share at the date of grant for options granted during the period from
    February 26, 1996 (inception) to September 30, 1996, for the years ended
    September 30, 1997 and 1998 and for the nine months ended June 30, 1999 were
    as follows:

<TABLE>
<CAPTION>
                                                     PERIOD FROM
                                                    FEBRUARY 26,
                                                        1996        YEAR ENDED SEPTEMBER
                                                   (INCEPTION) TO           30,             NINE MONTHS
                                                    SEPTEMBER 30,   --------------------  ENDED JUNE 30,
                                                        1996          1997       1998          1999
                                                   ---------------  ---------  ---------  ---------------
<S>                                                <C>              <C>        <C>        <C>
Weighted-average fair value of options granted
  with exercise prices equal to the market value
  of the stock at the date of grant..............     $    0.01     $    0.01  $    0.08     $    2.79

Weighted-average exercise price of options
  granted with exercise prices equal to the
  market value of the stock at the date of
  grant..........................................          0.05          0.05       0.50         10.32

Weighted-average fair value of options granted
  with exercise prices less than the market value
  of the stock at the date of grant..............                        0.41       1.60          4.54

Weighted-average exercise price of options
  granted with exercise prices less than the
  market value of the stock at the date of
  grant..........................................          0.05          0.05       0.28          1.13
</TABLE>

                                      F-19
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

8.  SHAREHOLDERS' EQUITY: (CONTINUED)
    The following table summarizes information about fixed-price options
    outstanding at June 30, 1999 as follows:

<TABLE>
<CAPTION>
                               WEIGHTED
                                AVERAGE      WEIGHTED                  WEIGHTED
                               REMAINING      AVERAGE                   AVERAGE
   EXERCISE       NUMBER      CONTRACTUAL    EXERCISE      NUMBER     EXERCISABLE
    PRICES      OUTSTANDING      LIFE          PRICE     EXERCISABLE     PRICE
- --------------  -----------  -------------  -----------  -----------  -----------
<S>             <C>          <C>            <C>          <C>          <C>
    $0.05          751,096          8.28     $    0.05       33,001    $    0.05
  $0.25-0.50       472,449          8.58     $    0.32      112,700    $    0.44
  $0.75-1.50       841,544          9.33     $    1.21       94,002    $    1.15
  $2.50-5.00       108,000          9.62     $    3.14          833    $    2.50
 $8.00-10.00       174,348          9.83     $    9.15          967    $    8.11
 $15.50-18.63       14,200          9.96     $   16.71        5,000    $   18.00
 $19.38-27.88        7,625          9.97     $   21.76
</TABLE>

    1999 EMPLOYEE STOCK PURCHASE PLAN

    In May 1999, the board of directors approved the adoption of the 1999
    Employee Stock Purchase Plan (the "Purchase Plan"). A total of 1,000,000
    shares of common stock has been reserved for issuance under the Purchase
    Plan. The Purchase Plan permits eligible employees to acquire shares of the
    Company's common stock through periodic payroll deductions of up to 15% of
    base compensation. No employee may purchase more than $25,000 worth of
    stock, determined at the fair market value of the shares at the time such
    option is granted, in one calendar year. The Purchase Plan will be
    implemented in a series of offering periods, each approximately 6 months in
    duration; provided, however, that the first offering period will commence on
    the effectiveness of the initial public offering and be approximately seven
    months in duration, ending on the last trading day on or before December 31,
    1999. The price at which the common stock may be purchased is 85% of the
    lesser of the fair market value of the Company's common stock on the first
    day of the applicable offering period or on the last day of the respective
    purchase period.

9.  COMMITMENTS:

    The Company is committed under non-cancelable operating leases for its
    current and former office space, which expire in 2002 and 1999,
    respectively. During 1998, the Company leased its former office space under
    a non-cancelable sub-leasing arrangement for amounts equal to the liability
    of the commitment, which expires in 1999. Additionally, the Company is
    committed under non-cancelable

                                      F-20
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

9.  COMMITMENTS: (CONTINUED)
    operating leases for certain office equipment. Minimum operating lease
    payments and sub-leasing receipts for future fiscal years, as of June 30,
    1999, are approximately as follows:

<TABLE>
<CAPTION>
                                                              OPERATING LEASE   OPERATING SUBLEASE
                                                                 PAYMENTS            RECEIPTS
                                                              ---------------   ------------------
                                                                         (IN THOUSANDS)
<S>                                                           <C>               <C>
1999........................................................      $  345               $18
2000........................................................         537
2001........................................................         587
2002........................................................         618
Thereafter..................................................       1,134
                                                                                        --
                                                                  ------
                                                                  $3,221               $18
                                                                                        --
                                                                                        --
                                                                  ------
                                                                  ------
</TABLE>

    In January 1999, the Company amended its operating lease to increase the
    amount of its current office space and extend the term through 2004. This
    increased the minimum operating lease payments to approximately $2.1
    million.

    Rent expense under noncancelable operating leases amounted to approximately
    $7,000 for the period from February 26, 1996 (inception) to September 30,
    1996, approximately $38,000 and $145,000 for the years ended September 30,
    1997 and 1998, respectively. Rent expense amounted to approximately $98,000
    and $308,000 for the nine months ended June 30, 1998 (unaudited) and 1999,
    respectively.

10.  RELATED PARTY TRANSACTIONS:

    In March 1999, the Company issued 150,000 shares of common stock to an
    officer of the Company in exchange for a note receivable. These shares were
    acquired by exercising stock options that vest over a period of four years.
    The note bears interest at a rate of 4.83%, is collateralized by the shares,
    partially guaranteed by the officer and is due in 2003. Under the pledge
    agreement, the Company has the obligation to repurchase any remaining
    unvested shares, and the note becomes due upon the officer's termination.
    Further, the shares may not be transferred until they are vested and paid
    for.

11.  SUBSEQUENT EVENTS

    In September 1999, the Board of Directors authorized management of the
    Company to file a Registration Statement with the Securities and Exchange
    Commission covering the proposed sale of additional shares of its common
    stock to the public.

    In July of 1999 the Company amended their existing lease of office space to
    add an additional 8,000 square feet, for a term of 84 months. The annual
    cost of this additional lease is approximately $164,000, subject to annual
    adjustments. Also in July of 1999 the Company entered into a new lease for
    approximately 84,000 square feet of office space in a building which is
    currently under construction. This lease will commence in July 1, 2000 with
    a term of 12 years. The annual cost of this lease is approximately
    $2,000,000, subject to annual adjustments. Also in July 1999, the Company
    entered into an outstanding secured irrevocable letter of credit with a bank
    in the amount of $2.5 million which collateralizes the Company's obligation
    to fund its lease commitment.

                                      F-21
<PAGE>
                               F5 NETWORKS, INC.

                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)

12.  SUPPLEMENTAL CASH FLOW INFORMATION:

    Supplemental disclosure of cash flow information is summarized below for the
    years ended September 30, 1997 and 1998, for the period from February 26,
    1996 (inception) to September 30, 1996, and for the nine months ended June
    30, 1998 (unaudited) and 1999:

<TABLE>
<CAPTION>
                                                                  PERIOD FROM
                                                                 FEBRUARY 26,                                 NINE MONTHS
                                                                     1996             YEAR ENDED                 ENDED
                                                                  (INCEPTION)        SEPTEMBER 30,             JUNE 30,
                                                                 TO SEPTEMBER    ---------------------   ---------------------
                                                                   30, 1996         1997        1998       1998        1999
                                                                 -------------     -----      --------   ---------   ---------
                                                                                        (IN THOUSANDS)
<S>                                                              <C>             <C>          <C>        <C>         <C>
                                                                                                         (UNAUDITED)
Noncash investing and financing activities:
  Equipment obtained through capital lease.....................       $43           $    11
  Disposal of property and equipment for note and relief of
    accounts payable...........................................        10
  Deferred gain on sale leaseback..............................         5
  Series A Convertible Preferred Stock issued for note.........        90
  Conversion of note payable and related accrued interest to
    Series B Convertible
    Preferred Stock............................................                                   $520     $520
  Value ascribed to warrants in conjunction with sale of
    Convertible Preferred Stock................................                          42        367      367
  Value ascribed to warrants issued with note payable..........                         109
  Conversion of note payable to common stock...................                                    209      209
  Note receivable from shareholder for exercise of options.....                                                         $750
  Unearned compensation........................................         4               238      1,945    1,098       4,063
  Write-off of accounts receivable.............................                                     30       30          78
  Sales returns................................................                                    193      117         556
Cash paid for interest.........................................                          19         30       16           2
</TABLE>

                                      F-22
<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                                2,000,000 SHARES

                                     [LOGO]

                                  COMMON STOCK
                                 -------------

                                   PROSPECTUS

                                 -------------

                               HAMBRECHT & QUIST

                         BANCBOSTON ROBERTSON STEPHENS

                            BEAR, STEARNS & CO. INC.

                              DAIN RAUSCHER WESSELS
                                A DIVISION OF DAIN RAUSCHER INCORPORATED

                               ------------------

                                          , 1999

                               ------------------

    YOU SHOULD RELY ONLY ON INFORMATION CONTAINED IN THIS PROSPECTUS. WE HAVE
NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION DIFFERENT FROM THAT
CONTAINED IN THIS PROSPECTUS. WE ARE OFFERING TO SELL, AND SEEKING OFFERS TO
BUY, SHARES OF COMMON STOCK ONLY IN JURISDICTIONS WHERE OFFERS AND SALES ARE
PERMITTED. THE INFORMATION CONTAINED IN THIS PROSPECTUS IS ACCURATE ONLY AS OF
THE DATE OF THIS PROSPECTUS, REGARDLESS OF THE TIME OF DELIVERY OF THIS
PROSPECTUS OR OF ANY SALE OF OUR COMMON STOCK.

    NO ACTION IS BEING TAKEN IN ANY JURISDICTION OUTSIDE THE UNITED STATES TO
PERMIT A PUBLIC OFFERING OF THE COMMON STOCK OR POSSESSION OR DISTRIBUTION OF
THIS PROSPECTUS IN ANY SUCH JURISDICTION. PERSONS WHO COME INTO POSSESSION OF
THIS PROSPECTUS IN JURISDICTIONS OUTSIDE THE UNITED STATES ARE REQUIRED TO
INFORM THEMSELVES ABOUT AND TO OBSERVE ANY RESTRICTIONS AS TO THIS OFFERING AND
THE DISTRIBUTION OF THIS PROSPECTUS APPLICABLE TO THAT JURISDICTION.

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
                                    PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 13. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

    The following table sets forth the costs and expenses, other than
underwriting discounts and commissions, payable by the Company in connection
with the sale of common stock being registered. All amounts are estimates except
the SEC registration fee, the NASD filing fee and the Nasdaq National Market
listing fee.

<TABLE>
<S>                                                                 <C>
SEC registration fee..............................................  $  41,881
NASD filing fee...................................................     15,565
Nasdaq National Market listing fee................................     10,000
Printing and engraving costs......................................    100,000
Legal fees and expenses...........................................     75,000
Accounting fees and expenses......................................     75,000
Blue Sky fees and expenses........................................      5,000
Transfer Agent and Registrar fees.................................      5,000
Miscellaneous expenses............................................     22,554
                                                                    ---------
  Total...........................................................  $ 350,000
                                                                    ---------
                                                                    ---------
</TABLE>

ITEM 14. INDEMNIFICATION OF DIRECTORS AND OFFICERS

    Sections 23B.08.500 through 23.B.08.600 of the Washington Business
Corporation Act (the "WBCA") authorize a court to award, or a corporation's
board of directors to grant, indemnification to directors and officers on terms
sufficiently broad to permit indemnification under certain circumstances for
liabilities arising under the Securities Act of 1933, as amended (the
"Securities Act"). The directors and officers of the registrant also may be
indemnified against liability they may incur for serving in that capacity
pursuant to a liability insurance policy maintained by the registrant for this
purpose.

    Section 23B.08.320 of the WBCA authorizes a corporation to limit a
director's liability to the corporation or its shareholders for monetary damages
for acts or omissions as a director, except in certain circumstances involving
intentional misconduct, knowing violations of law or illegal corporate loans or
distributions, or any transaction from which the director personally receives a
benefit in money, property or services to which the director is not legally
entitled. The registrant's second amended and restated articles of
incorporation, (Exhibit 3.2 hereto) contains provisions implementing, to the
fullest extent permitted by Washington law, these limitations on a director's
liability to the registrant and its shareholders.

    The registrant has entered into certain indemnification agreements with its
directors and certain of its officers, the form of which is attached as Exhibit
10.1 to this registration statement and incorporated herein by reference. The
indemnification agreements provide the registrant's directors and certain of its
officers with indemnification to the maximum extent permitted by the WBCA.

    The underwriting agreement (Exhibit 1.1 hereto) provides for indemnification
by the underwriters of the registrant and its executive officers and directors
and by the registrant of the Underwriters, for certain liabilities, including
liabilities arising under the Securities Act, in connection with matters
specifically provided in writing by the underwriters for inclusion in this
registration statement.

ITEM 15. RECENT SALES OF UNREGISTERED SECURITIES

    During the past three years, F5 has issued unregistered securities to a
limited number of persons, as described below. None of these transactions
involved any underwriters, underwriting discounts or

                                      II-1
<PAGE>
commissions, or any public offering, and F5 believes that each transaction was
exempt from the registration requirements of the Securities Act by virtue of
Section 4(2) thereof, Regulation D promulgated thereunder or Rule 701 pursuant
to compensatory benefit plans and contracts relating to compensation as provided
under Rule 701. The recipients of securities in each of these transactions
represented their intention to acquire the securities for investment only and
not with a view to or for sale in connection with any distribution thereof, and
appropriate legends were affixed to the share certificates and instruments
issued in these transactions. All recipients had adequate access to information
about F5, through their relationships with F5.

    Since March 31, 1996, F5 has issued and sold the following unregistered
securities:

    (1) From March 31, 1996 to July 2, 1999, F5 granted stock options to
purchase an aggregate of 5,019,448 shares of common stock at exercise prices
ranging from $0.05 to $37.00 per share to employees, consultants, directors and
other service providers pursuant to F5's 1998 Equity Incentive Plan, Amended and
Restated 1996 Stock Option Plan and Amended and Restated Directors' Nonqualified
Stock Option Plan. Prior to July 2, 1999 (the effective date of F5's
Registration Statement on Form S-8) options to purchase 901,341 shares were
exercised.

    (2) In May, August and December 1996 and April 1997, F5 sold an aggregate of
400,000 shares of Series A convertible preferred stock to 31 private investors
at an aggregate purchase price of $1,200,000 or $3.00 per share.

    (3) From May 15, 1996 to February 25, 1999, F5 issued warrants to four
private investors, one consultant and one customer to purchase an aggregate of
2,645,750 shares of common stock with a weighted average exercise price of
$0.79.

    (4) In September, October and November 1997, F5 sold an aggregate of
1,250,000 shares of Series B convertible preferred stock to three private
investors at an aggregate purchase price of $2,000,000 or $1.60 per share.

    (5) On April 15, 1998, F5 sold an aggregate of 156,250 shares of Series C
convertible preferred stock to one private investor at an aggregate purchase
price of $1,500,000 or $9.60 per share.

    (6) On August 21, 1998, F5 sold an aggregate of 1,138,438 shares of Series D
redeemable convertible preferred stock to three private investors at an
aggregate purchase price of $7,729,994 or $6.79 per share.

ITEM 16. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES

    (a)  EXHIBITS

<TABLE>
<CAPTION>
<S>        <C>
     1.1   Form of Underwriting Agreement.
     3.1*  Amended and Restated Articles of Incorporation of the Registrant, as
             amended.
     3.2*  Bylaws of the Registrant, as currently in effect.
     4.1*  Specimen Common Stock Certificate.
     5.1   Opinion of Heller Ehrman White & McAuliffe.
    10.1*  Form of Indemnification Agreement between the Registrant and each of
             its directors and certain of its officers.
    10.2*  1998 Equity Incentive Plan.
    10.3*  Form of Option Agreement under the 1998 Equity Incentive Plan.
    10.4*  1999 Employee Stock Purchase Plan.
    10.5*  Amended and Restated Directors' Nonqualified Stock Option Plan.
    10.6*  Form of Option Agreement under the Amended and Restated Directors'
             Nonqualified Stock Option Plan.
</TABLE>

                                      II-2
<PAGE>
<TABLE>
<CAPTION>
    10.7*  Amended and Restated 1996 Stock Option Plan.
<S>        <C>
    10.8*  Form of Option Agreement under the Amended and Restated 1996 Stock
             Option Plan.
    10.9*  1999 Non-Employee Directors' Stock Option Plan.
   10.10*  Form of Option Agreement under 1999 Non-Employee Directors' Stock
             Option Plan.
   10.11*  Lease Agreement, dated October 9, 1997, between the Registrant and
             First Avenue West Building L.L.C.
   10.12*  First Amendment to Lease Agreement, dated July 23, 1998 between
             Registrant and First Avenue West Building L.L.C.
   10.13*  Second Amendment to Lease Agreement, dated September 30, 1998
             between Registrant and First Avenue West Building L.L.C.
   10.14*  Third Amendment to Lease Agreement, dated January 6, 1999, between
             the Registrant and First Avenue West Building L.L.C.
    10.15  Fourth Amendment to Lease Agreement, dated July 2, 1999 between the
             Registrant and First Avenue West Building L.L.C.
    10.16  Fifth Amemdment to Lease Agreement, dated July 5, 1999 between the
             Registrant and First Avenue West Building L.L.C.
    10.17  Office Lease Agreement dated July 31, 1999, between Registrant and
             401 Elliott West LLC
   10.18*  Agreement, dated February 19, 1999, between the Registrant and
             Steven Goldman.
   10.19*  Form of Common Stock Purchase Warrant.
   10.20*  Common Stock Warrant, dated March 15, 1997 between Registrant and
             Brittania Holdings Limited.
   10.21*  Common Stock Warrant, dated August 5, 1997, between Registrant and
             Brittania Holdings Limited.
   10.22*  Common Stock Warrant, dated February 25, 1999, between Registrant
             and PSINet, Inc., as amended.
   10.23*  Investor Rights Agreement, dated August 21, 1998, between Registrant
             and certain holders of the Registrant's Series A Preferred Stock,
             Series B Preferred Stock, Series C Preferred Stock and Series D
             Preferred Stock.
   10.24*  Promissory Term Note, dated January 6, 1998, between Registrant and
             Jeffrey S. Hussey, as amended.
   10.25*  Early Exercise Stock Purchase Agreement, dated March 10, 1999,
             between Registrant and Robert J. Chamberlain.
    23.1   Consent of PricewaterhouseCoopers LLP, Independent Accountants.
    23.2   Consent of Counsel (included in Exhibit 5.1).
    24.1   Power of Attorney (contained on signature page).
    27.1   Financial Data Schedule.
</TABLE>

* Incorporated by reference from Registration Statement on Form S-1, File No.
333-75817

ITEM 17. UNDERTAKINGS

    The registrant hereby undertakes to provide to the underwriters at the
closing specified in the underwriting agreement certificates in the
denominations and registered in the names as required by the underwriters to
permit prompt delivery to each purchaser.

    Insofar as indemnification by the registrant for liabilities arising under
the Securities Act may be permitted to directors, officers and controlling
persons of the registrant pursuant to the provisions referenced in Item 14 of
this registration statement or otherwise, the registrant has been advised that
in

                                      II-3
<PAGE>
the opinion of the Securities and Exchange Commission this indemnification is
against public policy as expressed in the Securities Act, and is, therefore,
unenforceable. In the event that a claim for indemnification against these
liabilities (other than the payment by the registrant of expenses incurred or
paid by a director, officer, or controlling person of the registrant in the
successful defense of any action, suit or proceeding) is asserted by a director,
officer or controlling person in connection with the securities being registered
hereunder, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether this indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of this issue.

    The registrant hereby undertakes that:

        (1) For purposes of determining any liability under the Securities Act,
    the information omitted from the form of Prospectus filed as part of this
    registration statement in reliance upon Rule 430A and contained in a form of
    Prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or
    497(h) under the Securities Act will be deemed to be part of this
    registration statement as of the time it was declared effective.

        (2) For the purpose of determining any liability under the Securities
    Act, each post-effective amendment that contains a form of Prospectus shall
    be deemed to be a new registration statement relating to the securities
    offered therein, and the offering of these securities at that time shall be
    deemed to be the initial bona fide offering thereof.

                                      II-4
<PAGE>
                                   SIGNATURES

    Pursuant to the requirements of the Securities Act of 1933, as amended, the
registrant has duly caused this Registration Statement to be signed on its
behalf by the undersigned, thereinto duly authorized, in the City of Seattle,
State of Washington, on the 9th day of September, 1999.

<TABLE>
<S>                             <C>  <C>
                                F5 NETWORKS, INC.

                                By:            /s/ JEFFREY S. HUSSEY
                                     -----------------------------------------
                                                 Jeffrey S. Hussey
                                       CHIEF EXECUTIVE OFFICER AND PRESIDENT
</TABLE>

                               POWER OF ATTORNEY

    Each person whose individual signature appears below hereby authorizes and
appoints Jeffrey S. Hussey and Robert J. Chamberlain, and each of them, with
full power of substitution and resubstitution and full power to act without the
other, as his true and lawful attorney-in-fact and agent to act in his name,
place and stead and to execute in the name and on behalf of each person,
individually and in each capacity stated below, and to file, any and all
amendments to this Registration Statement, including any and all post-effective
amendments and amendments thereto any registration statement relating to the
same offering as this Registration Statement that is to be effective upon filing
pursuant to Rule 462(b) under the Securities Act of 1933, as amended, and to
file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents, and each of them, full power and authority to do
and perform each and every act and thing, ratifying and confirming all that said
attorneys-in-fact and agents or any of them or their or his substitute or
substitutes may lawfully do or cause to be done by virtue thereof.

    Pursuant to the requirements of the Securities Act of 1933, as amended, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated:

<TABLE>
<CAPTION>
          SIGNATURE                       TITLE                    DATE
- ------------------------------  --------------------------  -------------------

<C>                             <S>                         <C>
                                Chairman of the Board,
    /s/ JEFFREY S. HUSSEY         Chief Executive Officer
- ------------------------------    and President (Principal   September 9, 1999
      Jeffrey S. Hussey           Executive Officer)

                                Vice President of Finance,
  /s/ ROBERT J. CHAMBERLAIN       Chief Financial Officer
- ------------------------------    and Treasurer (Principal   September 9, 1999
    Robert J. Chamberlain         Finance and Accounting
                                  Officer)

    /s/ CARLTON G. AMDAHL
- ------------------------------  Director                     September 9, 1999
      Carlton G. Amdahl
</TABLE>

                                      II-5
<PAGE>
<TABLE>
<CAPTION>
          SIGNATURE                       TITLE                    DATE
- ------------------------------  --------------------------  -------------------

<C>                             <S>                         <C>
     /s/ KARL D. GUELICH
- ------------------------------  Director                     September 9, 1999
       Karl D. Guelich

    /s/ ALAN J. HIGGINSON
- ------------------------------  Director                     September 9, 1999
      Alan J. Higginson

      /s/ SONJA L. HOEL
- ------------------------------  Director                     September 9, 1999
        Sonja L. Hoel

     /s/ KENT L. JOHNSON
- ------------------------------  Director                     September 9, 1999
       Kent L. Johnson
</TABLE>

                                      II-6
<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<S>        <C>
     1.1   Form of Underwriting Agreement.
     3.1*  Amended and Restated Articles of Incorporation of the Registrant, as amended.
     3.2*  Bylaws of the Registrant, as currently in effect.
     4.1*  Specimen Common Stock Certificate.
     5.1   Opinion of Heller Ehrman White & McAuliffe.
    10.1*  Form of Indemnification Agreement between the Registrant and each of its
             directors and certain of its officers.
    10.2*  1998 Equity Incentive Plan.
    10.3*  Form of Option Agreement under the 1998 Equity Incentive Plan.
    10.4*  1999 Employee Stock Purchase Plan.
    10.5*  Amended and Restated Directors' Nonqualified Stock Option Plan.
    10.6*  Form of Option Agreement under the Amended and Restated Directors'
             Nonqualified Stock Option Plan.
    10.7*  Amended and Restated 1996 Stock Option Plan.
    10.8*  Form of Option Agreement under the Amended and Restated 1996 Stock Option
             Plan.
    10.9*  1999 Non-Employee Directors' Stock Option Plan.
   10.10*  Form of Option Agreement under 1999 Non-Employee Directors' Stock Option
             Plan.
   10.11*  Lease Agreement, dated October 9, 1997, between the Registrant and First
             Avenue West Building L.L.C.
   10.12*  First Amendment to Lease Agreement, dated July 23, 1998 between Registrant
             and First Avenue West Building L.L.C.
   10.13*  Second Amendment to Lease Agreement, dated September 30, 1998 between
             Registrant and First Avenue West Building L.L.C.
   10.14*  Third Amendment to Lease Agreement, dated January 6, 1999, between the
             Registrant and First Avenue West Building L.L.C.
    10.15  Fourth Amendment to Lease Agreement, dated July 2, 1999 between the
             Registrant and First Avenue West Building L.L.C.
    10.16  Fifth Amemdment to Lease Agreement, dated July 5, 1999 between the Registrant
             and First Avenue West Building L.L.C.
    10.17  Office Lease Agreement dated July 31, 1999, between Registrant and 401
             Elliott West LLC
   10.18*  Agreement, dated February 19, 1999, between the Registrant and Steven
             Goldman.
   10.19*  Form of Common Stock Purchase Warrant.
   10.20*  Common Stock Warrant, dated March 15, 1997 between Registrant and Brittania
             Holdings Limited.
   10.21*  Common Stock Warrant, dated August 5, 1997, between Registrant and Brittania
             Holdings Limited.
   10.22*  Common Stock Warrant, dated February 25, 1999, between Registrant and PSINet,
             Inc., as amended.
   10.23*  Investor Rights Agreement, dated August 21, 1998, between Registrant and
             certain holders of the Registrant's Series A Preferred Stock, Series B
             Preferred Stock, Series C Preferred Stock and Series D Preferred Stock.
   10.24*  Promissory Term Note, dated January 6, 1998, between Registrant and Jeffrey
             S. Hussey, as amended.
   10.25*  Early Exercise Stock Purchase Agreement, dated March 10, 1999, between
             Registrant and Robert J. Chamberlain.
    23.1   Consent of PricewaterhouseCoopers LLP, Independent Accountants.
    23.2   Consent of Counsel (included in Exhibit 5.1).
    24.1   Power of Attorney (contained on signature page).
</TABLE>
<PAGE>
<TABLE>
<S>        <C>
    27.1   Financial Data Schedule.
</TABLE>

* Incorporated by reference from Registration Statement on Form S-1, File No.
333-75817

<PAGE>

                       F5 NETWORKS, INC.

                      2,000,000 SHARES (1)

                          COMMON STOCK


                      UNDERWRITING AGREEMENT

                                                           September ___, 1999

HAMBRECHT & QUIST LLC
BANCBOSTON ROBERTSON STEPHENS INC
BEAR, STEARNS & CO., INC.
DAIN RAUSCHER WESSELS, a division of Dain Rauscher Incorporated
  c/o Hambrecht & Quist LLC
  One Bush Street
  San Francisco, CA 94104

Ladies and Gentlemen:

       F5 Networks, Inc., a Washington corporation (herein called the Company),
proposes to issue and sell 500,000 shares of its authorized but unissued Common
Stock, no par value (herein called the "Common Stock"), and the shareholders of
the Company named in part A of Schedule II hereto (herein collectively called
the "Primary Selling Securityholders," which term shall include, except where
otherwise noted, each shareholder named as an Affiliated Selling Securityholder
in Schedule II hereto, herein called an "Affiliated Selling Securityholder" and
collectively, the "Affiliated Selling Securityholders") severally propose to
sell an aggregate of 1,500,000 shares of Common Stock of the Company (said
2,000,000 shares of Common Stock being herein called the "Underwritten Stock").
The Company and certain shareholders of the Company named in Part B of Schedule
II hereto ("Additional Selling Securityholders,") propose to grant to the
Underwriters (as hereinafter defined) an option to purchase up to 300,000
additional shares of Common Stock, said 300,000 shares of Common Stock being
herein called "Option Stock" and with the Underwritten Stock herein collectively
called the "Stock."  The Common Stock is more fully described in the
Registration Statement and the Prospectus hereinafter mentioned.  The Primary
Selling Securityholders and the Additional Selling Securityholders shall
collectively be referred to herein as the "Selling Securityholders."

       The Company and the Selling Securityholders severally hereby confirm the
agreements made with respect to the purchase of the Stock by the several
underwriters, for whom you are acting, named in Schedule I hereto (herein
collectively called the Underwriters, which term shall also include any
underwriter purchasing Stock pursuant to Section 3(b) hereof).  You represent
and warrant that you have been authorized by each of the other Underwriters to
enter into this Agreement on its behalf and to act for it in the manner herein
provided.

       1.     REGISTRATION STATEMENT.  The Company has filed with the Securities
and Exchange Commission (herein called the "Commission") a registration
statement on Form S-1 (No. 333-______), including the related preliminary
prospectus, for the registration under the Securities Act of 1933, as amended
(herein called the "Securities Act") of the Stock.  Copies of such registration
statement and of each amendment thereto, if any, including the related
preliminary prospectus (meeting the requirements of Rule 430A of the rules and
regulations of the Commission) heretofore filed by the Company with the
Commission have been delivered to you.

- -----------------
(1)    Plus an option to purchase from the Company and the Additional Selling
       Securityholders up to 300,000 additional shares to cover over-allotments.

                                     2
<PAGE>

       The term Registration Statement as used in this agreement shall mean such
registration statement, including all exhibits and financial statements, all
information omitted therefrom in reliance upon Rule 430A and contained in the
Prospectus referred to below, in the form in which it became effective, and any
registration statement filed pursuant to Rule 462(b) of the rules and
regulations of the Commission with respect to the Stock (herein called a
"Rule 462(b) Registration Statement"), and, in the event of any amendment
thereto after the effective date of such registration statement (herein called
the "Effective Date"), shall also mean (from and after the effectiveness of such
amendment) such registration statement as so amended (including any Rule 462(b)
registration statement).  The term Prospectus as used in this Agreement shall
mean the prospectus relating to the Stock first filed with the Commission
pursuant to Rule 424(b) and Rule 430A (or if no such filing is required, as
included in the Registration Statement) and, in the event of any supplement or
amendment to such prospectus after the Effective Date, shall also mean (from and
after the filing with the Commission of such supplement or the effectiveness of
such amendment) such prospectus as so supplemented or amended.  The term
Preliminary Prospectus as used in this Agreement shall mean each preliminary
prospectus included in such registration statement prior to the time it becomes
effective.

       The Registration Statement has been declared effective under the
Securities Act, and no post-effective amendment to the Registration Statement
has been filed as of the date of this Agreement. The Company has caused to be
delivered to you copies of each Preliminary Prospectus and has consented to the
use of such copies for the purposes permitted by the Securities Act.

       2.     REPRESENTATIONS AND WARRANTIES OF THE COMPANY AND THE SELLING
SECURITYHOLDERS.

              (a)    The Company hereby represents and warrants as follows:

                     (i)    Each of the Company and its subsidiary has been duly
incorporated and is validly existing as a corporation in good standing under the
laws of the jurisdiction of its incorporation, has full corporate power and
authority to own or lease its properties and conduct its business as described
in the Registration Statement and the Prospectus and as being conducted, and is
duly qualified as a foreign corporation and in good standing in all
jurisdictions in which the character of the property owned or leased or the
nature of the business transacted by it makes qualification necessary (except
where the failure to be so qualified would not have a material adverse effect on
the business, properties, financial condition or results of operations of the
Company (a "Material Adverse Effect")).

                     (ii)   Since the respective dates as of which information
is given in the Registration Statement and the Prospectus, there has not been
any material adverse change in the business, properties, financial condition or
results of operations of the Company whether or not arising from transactions in
the ordinary course of business, other than as set forth in the Registration
Statement and the Prospectus, and since such dates, except in the ordinary
course of business, the Company has not entered into any material transaction
not referred to in the Registration Statement and the Prospectus.

                     (iii)  The Commission has not issued any order preventing
or suspending the use of any Preliminary Prospectus relating to the proposed
offering of the Stock nor instituted or threatened instituting proceedings for
that purpose.  The Registration Statement and the Prospectus comply, and on the
Closing Date (as hereinafter defined) and any later date on which Option Stock
is to be purchased, the Prospectus will comply, in all material respects, with
the provisions of the Securities Act and the rules and regulations of the
Commission thereunder; on the Effective Date, the Registration Statement did not
contain any untrue statement of a material fact and did not omit to state any
material fact required to be stated therein or necessary in order to make the
statements therein not misleading; and, on the Effective Date the Prospectus did
not and, on the Closing Date and any later date on which Option Stock is to be
purchased, will not contain any untrue statement of a material fact or omit to
state any material fact necessary in order to make the statements therein, in
the light of the circumstances under which they were made, not misleading;
PROVIDED, HOWEVER, that none of the representations and warranties in this
subparagraph (iii) shall apply to statements in, or omissions from, the
Registration Statement or the Prospectus made in reliance upon and in conformity
with information herein or otherwise furnished in writing to the Company by or
on behalf of the Underwriters for use in the Registration Statement or the
Prospectus.

                     (iv)   The Company's authorized, issued and outstanding
capitalization as of June 30, 1999 is as set forth under the caption
"Capitalization" in the Prospectus.  The Stock is duly and validly authorized,

                                     3
<PAGE>

and, when issued and sold to the several Underwriters and upon the delivery of
and payment for such shares of the Stock, as provided herein, will be duly and
validly issued, fully paid and nonassessable, and the Underwriters will receive
good and marketable title thereto, free and clear of all liens, encumbrances,
equities, security interests and claims whatsoever.  The capital stock conforms
in all material respects to the description thereof contained in the Prospectus.
No further approval or authority of the shareholders or the Board of Directors
of the Company will be required for the issuance and sale of the Stock by the
Company as contemplated herein or to the knowledge of the Company for the
transfer and sale of the Stock to be sold by the Selling Securityholders.  The
shares of capital stock outstanding prior to the issuance of the Underwritten
Stock and, if any, the Option Stock have been duly authorized and are validly
issued, fully paid and nonassessable.

                     (v)    Prior to the Closing Date, the Stock to be issued
and sold under this Agreement will be authorized for listing by the Nasdaq
National Market (herein called "NNM") upon official notice of issuance of the
Stock.

                     (vi)   Except as disclosed in the Registration Statement,
and except for stock options and shares of Common Stock granted or purchased in
the ordinary course of business after June 30, 1999 pursuant to the equity
incentive plans disclosed in the Registration Statement ("Option Plans"), the
Company does not have outstanding any options or warrants to purchase, or any
preemptive rights, or other rights to subscribe or to purchase or rights of co-
sale, any securities or obligations convertible or exercisable into, or any
contracts or commitments to issue or sell or register for sale, shares of its
capital stock or any such options, warrants, rights, convertible securities,
exercisable securities or obligations.

                     (vii)  PricewaterhouseCoopers LLP, who have certified the
consolidated financial statements included in the Registration Statement, have
represented to the Company that they are, and the Company has no reason to
believe that such representation is incorrect, independent public accountants as
required by the Securities Act and the rules and regulations of the Commission
thereunder.

                     (viii) The financial statements of the Company, together
with related notes and schedules as set forth in the Registration Statement
("Financial Statements"), present fairly the financial position and the results
of operations of the Company, at the indicated dates and for the indicated
periods. The Financial Statements have been prepared in accordance with
generally accepted accounting principles, consistently applied throughout the
periods involved, and all adjustments necessary for a fair presentation of
results for such periods have been made. The selected and summary financial data
contained in the Registration Statement and the financial information set forth
under the caption "Management's Discussion and Analysis of Financial Condition
and Results of Operations" present fairly the information shown therein and have
been compiled on a basis consistent with the Financial Statements.  Other than
as set forth in the Financial Statements, the Company has no material
liabilities, contingent or otherwise, other than liabilities incurred in the
ordinary course of business and described in the Registration Statement.

                     (ix)   Each of the Company and its subsidiary has filed all
tax returns required to be filed and has paid or is contesting in good faith all
taxes shown thereon as due, and there is no tax deficiency that has been or
might be asserted against the Company or its subsidiary that will or might have
a Material Adverse Effect as of the date hereof, and all tax liabilities are
adequately provided for in the Financial Statements of the Company as of the
date thereof.

                     (x)    The Company is not in violation or default under any
provision of its Articles of Incorporation or Bylaws as of the Closing Date and
any later date upon which the Option Stock is purchased, or any indenture,
license, mortgage, lease, franchise, permit, deed of trust or other agreement or
instrument to which the Company is a party or by which the Company or any of its
properties is bound or may be affected, except where such violation or default
would not have a Material Adverse Effect.

                     (xi)   The Company has full legal right, power and
authority to enter into this Agreement and perform the transactions contemplated
hereby. This Agreement has been duly authorized, executed and delivered by the
Company and is a valid and binding agreement on the part of the Company,
enforceable in accordance with its terms, except as rights to indemnity and
contribution hereunder may be limited by applicable laws and except as the
enforcement hereof may be limited by applicable bankruptcy, insolvency,
reorganization,

                                     4
<PAGE>

moratorium or other similar laws affecting creditors' rights generally, or by
general equitable principles. The execution and performance of this Agreement
and the consummation of the transactions herein contemplated, including, but
not limited to, the issuance and sale of the Stock by the Company and the sale
of the Stock by the Selling Securityholders do not and will not: (i) conflict
with, or result in a breach of, or violation of, any of the terms or
provisions of, or constitute, either by itself or upon notice or the passage
of time or both, a default under, any indenture, license, mortgage, lease,
franchise, permit, deed of trust or other agreement or instrument to which the
Company is a party or by which the Company or any of its properties is bound
or may be affected, except where such breach, violation or default would not
have a Material Adverse Effect, (ii) violate any of the provisions of the
Articles of Incorporation or Bylaws of the Company in effect as of the Closing
Date and any later date upon which the Option Stock is purchased, (iii)
violate any order, judgment, statute, rule or regulation applicable to the
Company or of any regulatory, administrative or governmental body or agency
having jurisdiction over the Company or any of its properties or assets,  or
(iv) result in the creation or imposition of any lien, charge or encumbrance
upon any assets or properties of the Company.

                     (xii)  Any consent, approval, authorization, order,
registration, filing, qualification, license or permit of or with any court or
any public, governmental or regulatory agency or body having jurisdiction over
the Company or any of its properties or assets which is required for the
execution, delivery and performance of this Agreement or the consummation of the
transactions contemplated hereby, including the issuance, sale and delivery of
the Stock to be issued, sold and delivered by the Company hereunder, have been
obtained, including the registration of the Stock under the Securities Act,
listing of the shares on the NNM and such consents, approvals, authorizations,
orders, registrations, filings, qualifications, licenses and permits as may be
required under state securities or Blue Sky laws in connection with the purchase
and distribution of the Stock by the Underwriters.

                     (xiii) There is no pending or, to the Company's knowledge,
threatened action, suit, claim or proceeding against the Company or its
subsidiary or any of its respective officers or any of its respective
properties, assets or rights before any court or governmental agency or body or
otherwise which (i) might have a Material Adverse Effect, (ii) might prevent
consummation of the transactions contemplated hereby or (iii) is required to be
disclosed in the Registration Statement and not otherwise disclosed; and there
are no contracts or documents of the Company that are required to be described
in the Prospectus or to be filed as exhibits to the Registration Statement which
have not been fairly and accurately described in all material respects in the
Prospectus and filed as exhibits to the Registration Statement. The contracts so
described in the Prospectus are in full force and effect on the date hereof, and
neither the Company nor, to the Company's knowledge, any other party is in
breach of or default under any of such contracts.

                     (xiv)  Other than as set forth in the Registration
Statement, no claim is pending or, to the Company's knowledge, threatened to the
effect that the present or past operations of the Company or its subsidiary
infringe upon or conflict with the rights of others with respect to any
licenses, patents, patent rights, patent applications, trademarks, trademark
applications, trade names, copyrights, trade secrets, drawings, schematics,
applications, technology, know-how and other tangible and intangible proprietary
information or material ("Intellectual Property") which would impair the ability
of the Company or its subsidiary to conduct its respective businesses as
currently conducted; no claim is pending or, to the Company's knowledge,
threatened regarding the Company's or its subsidiary's ownership or other
interest in, or rights under, any Intellectual Property which is necessary in
any respect to permit the Company or its subsidiary or its subsidiary to conduct
its businesses as currently conducted; and, no claim is pending or, to the
Company's knowledge, threatened to the effect that any Intellectual Property
owned by or licensed to the Company or its subsidiary is invalid or
unenforceable.  Except as disclosed in the Prospectus, the Company and its
subsidiary owns, or has licensed or otherwise has sufficient rights to, all
Intellectual Property used or proposed to be used in the business of the Company
or its subsidiary as currently conducted.  Except as otherwise disclosed in the
Prospectus, no contract, agreement or understanding between the Company and any
other party exists which would impede or prevent in any respect the continued
use by the Company or its subsidiary of the entire right, title and interest of
the Company or its subsidiary in and to any Intellectual Property used in the
business of the Company or its subsidiary as currently conducted.

                     (xv)   The Company has not taken and will not take,
directly or indirectly, any action designed to or that might be reasonably
expected to cause or result in stabilization or manipulation of the price of the
Common Stock to facilitate the sale or resale of the Stock.

                                     5
<PAGE>

                     (xvi)  Except as described in the Prospectus, no holder of
securities of the Company has any rights to the registration of securities of
the Company because of the filing of the Registration Statement or otherwise in
connection with the sale of the Stock contemplated hereby, other than those that
have been expressly waived prior to the date hereof.  There are no registration
rights with respect to the sale and issuance of the Stock, other than those that
have been expressly waived prior to the date hereof.

                     (xvii) The Company is not an "investment company" or a
company "controlled" by an "investment company" within the meaning of the
Investment Company Act of 1940, as amended, and the rules and regulations
thereunder.

              (b)    Each of the Selling Securityholders, severally and not
jointly, hereby represents and warrants as follows:

                     (i)    Such Selling Securityholder has good and marketable
title to all the shares of Stock to be sold by such Selling Securityholder
hereunder, free and clear of all liens, encumbrances, equities, security
interests and claims whatsoever, with full right and authority to deliver the
same hereunder, subject, in the case of each Selling Securityholder, to the
rights of American Stock Transfer & Trust Company, as custodian (herein called
the "Custodian"), and that upon the delivery of and payment for such shares of
the Stock hereunder, the several Underwriters will receive good and marketable
title thereto, free and clear of all liens, encumbrances, equities, security
interests and claims whatsoever.

                     (ii)   Certificates in negotiable form for the shares of
the Stock to be sold by such Selling Securityholder have been placed in custody
under a Custody Agreement for delivery under this Agreement with the Custodian;
such Selling Securityholder specifically agrees that the shares of the Stock
represented by the certificates so held in custody for such Selling
Securityholder are subject to the interests of the several Underwriters and the
Company, that the arrangements made by such Selling Securityholder for such
custody, including the Power of Attorney provided for in such Custody Agreement,
are to that extent irrevocable, and that the obligations of such Selling
Securityholder shall not be terminated by any act of such Selling Securityholder
or by operation of law, whether by the death or incapacity of such Selling
Securityholder (or, in the case of a Selling Securityholder that is not an
individual, the dissolution or liquidation of such Selling Securityholder) or
the occurrence of any other event; if any such death, incapacity, dissolution,
liquidation or other such event should occur before the delivery of such shares
of the Stock hereunder, certificates for such shares of the Stock shall be
delivered by the Custodian in accordance with the terms and conditions of this
Agreement as if such death, incapacity, dissolution, liquidation or other event
had not occurred, regardless of whether the Custodian shall have received notice
of such death, incapacity, dissolution, liquidation or other event.

              (c)    Each of the Affiliated Selling Securityholders hereby
represents and warrants that such Affiliated Selling Securityholder has reviewed
the Registration Statement and Prospectus and, although such Affiliated Selling
Securityholder has not independently verified the accuracy or completeness of
all the information contained therein, nothing has come to the attention of such
Affiliated Selling Securityholder that would lead such Affiliated Selling
Securityholder to believe that on the Effective Date, the Registration Statement
contained any untrue statement of a material fact or omitted to state any
material fact required to be stated therein or necessary in order to make the
statements therein not misleading; and, on the Effective Date the Prospectus
contained and, on the Closing Date and any later date on which Option Stock is
to be purchased, contains any untrue statement of a material fact or omitted or
omits to state any material fact necessary in order to make the statements
therein, in the light of the circumstances under which they were made, not
misleading; PROVIDED, HOWEVER, that none of the representations and warranties
in this paragraph (c) shall apply to statements in, or omissions from, the
Registration Statement or the Prospectus made in reliance upon and in conformity
with information herein or otherwise furnished in writing to the Company by or
on behalf of the Underwriters for use in the Registration Statement or the
Prospectus.

       3.     PURCHASE OF THE STOCK BY THE UNDERWRITERS.

              (a)    On the basis of the representations and warranties and
subject to the terms and conditions herein set forth, the Company agrees to
issue and sell 500,000 shares of the Underwritten Stock to the Underwriters, the
Primary Selling Securityholders agree to sell to the Underwriters the number of
shares of the Underwritten Stock

                                     6
<PAGE>

set forth in Schedule II opposite the name of such Primary Selling
Securityholders, and each of the Underwriters agrees to purchase from the
Company and the Primary Selling Securityholders the respective aggregate
number of shares of Underwritten Stock set forth opposite their names in
Schedule I.  The price at which such shares of Underwritten Stock shall be
sold by the Company and the Primary Selling Securityholders and purchased by
the Underwriters shall be [_______] per share.  The obligation of each
Underwriter to the Company and the Primary Selling Securityholders shall be to
purchase from the Company and the Primary Selling Securityholders that number
of shares of the Underwritten Stock which represents the same proportion of
the total number of shares of the Underwritten Stock to be sold by each of the
Company and the Primary Selling Securityholders pursuant to this Agreement as
the number of shares of the Underwritten Stock set forth opposite the name of
such Underwriter in Schedule I hereto represents of the total number of shares
of the Underwritten Stock to be purchased by all Underwriters pursuant to this
Agreement, as adjusted by Hambrecht & Quist LLC in such manner as Hambrecht &
Quist LLC deems advisable to avoid fractional shares.  In making this
Agreement, each Underwriter is contracting severally and not jointly; except
as provided in paragraphs (b) and (c) of this Section 3, the agreement of each
Underwriter is to purchase only the respective number of shares of the
Underwritten Stock specified in Schedule I.

              (b)    If for any reason one or more of the Underwriters shall
fail or refuse (otherwise than for a reason sufficient to justify the
termination of this Agreement under the provisions of Section 8 or 9 hereof) to
purchase and pay for the number of shares of the Stock agreed to be purchased by
such Underwriter or Underwriters, the Company or the Selling Securityholders
shall immediately give notice thereof to you, and the non-defaulting
Underwriters shall have the right within 24 hours after the receipt by you of
such notice to purchase, or procure one or more other Underwriters to purchase,
in such proportions as may be agreed upon between you and such purchasing
Underwriter or Underwriters and upon the terms herein set forth, all or any part
of the shares of the Stock which such defaulting Underwriter or Underwriters
agreed to purchase.  If the non-defaulting Underwriters fail so to make such
arrangements with respect to all such shares and portion, the number of shares
of the Stock which each non-defaulting Underwriter is otherwise obligated to
purchase under this Agreement shall be automatically increased on a pro rata
basis to absorb the remaining shares and portion which the defaulting
Underwriter or Underwriters agreed to purchase; PROVIDED, HOWEVER, that the non-
defaulting Underwriters shall not be obligated to purchase the shares and
portion which the defaulting Underwriter or Underwriters agreed to purchase if
the aggregate number of such shares of the Stock exceeds 10% of the total number
of shares of the Stock which all Underwriters agreed to purchase hereunder.  If
the total number of shares of the Stock which the defaulting Underwriter or
Underwriters agreed to purchase shall not be purchased or absorbed in accordance
with the two preceding sentences, the Company and the Selling Securityholders
shall have the right, within 24 hours next succeeding the 24-hour period above
referred to, to make arrangements with other underwriters or purchasers
satisfactory to you for purchase of such shares and portion on the terms herein
set forth.  In any such case, either you or the Company and the Selling
Securityholders shall have the right to postpone the Closing Date determined as
provided in Section 5 hereof for not more than seven business days after the
date originally fixed as the Closing Date pursuant to said Section 5 in order
that any necessary changes in the Registration Statement, the Prospectus or any
other documents or arrangements may be made.  If neither the non-defaulting
Underwriters nor the Company and the Selling Securityholders shall make
arrangements within the 24-hour periods stated above for the purchase of all the
shares of the Stock which the defaulting Underwriter or Underwriters agreed to
purchase hereunder, this Agreement shall be terminated without further act or
deed and without any liability on the part of the Company or the Selling
Securityholders to any non-defaulting Underwriter and without any liability on
the part of any non-defaulting Underwriter to the Company or the Selling
Securityholders. Nothing in this paragraph (b), and no action taken hereunder,
shall relieve any defaulting Underwriter from liability in respect of any
default of such Underwriter under this Agreement.

              (c)    On the basis of the representations, warranties and
covenants herein contained, and subject to the terms and conditions herein set
forth, the Company and the Additional Selling Securityholders grant an option to
the several Underwriters to purchase, severally and not jointly, up to 300,000
shares in the aggregate of the Option Stock from the Company and such Additional
Selling Securityholders at the same price per share as the Underwriters shall
pay for the Underwritten Stock.  Said option may be exercised only to cover
over-allotments in the sale of the Underwritten Stock by the Underwriters and
may be exercised in whole or in part at any time (but not more than once) on or
before the thirtieth day after the date of this Agreement upon written or
telegraphic notice by you to the Company setting forth the aggregate number of
shares of the Option Stock as to which the several Underwriters are exercising
the option.  Delivery of certificates for the shares of Option Stock, and
payment therefor, shall be made as provided in Section 5 hereof.  The number of
shares of the Option Stock to

                                     7
<PAGE>

be purchased by each Underwriter shall be the same percentage of the total
number of shares of the Option Stock to be purchased by the several
Underwriters as such Underwriter is purchasing of the Underwritten Stock, as
adjusted by you in such manner as you deem advisable to avoid fractional
shares.

       4.     OFFERING BY UNDERWRITERS.

              (a)    The terms of the public offering by the Underwriters of the
Stock to be purchased by them shall be as set forth in the Prospectus.  The
Underwriters may from time to time change the public offering price after the
closing of the public offering and increase or decrease the concessions and
discounts to dealers as they may determine.

              (b)    The information set forth in the last paragraph on the
front cover page and under "Underwriting" in the Registration Statement, any
Preliminary Prospectus and the Prospectus relating to the Stock filed by the
Company (insofar as such information relates to the Underwriters) constitutes
the only information furnished by the Underwriters to the Company for inclusion
in the Registration Statement, any Preliminary Prospectus, and the Prospectus,
and you on behalf of the respective Underwriters represent and warrant to the
Company that the statements made therein are correct.

       5.     DELIVERY OF AND PAYMENT FOR THE STOCK.

              (a)    Delivery of certificates for the shares of the Underwritten
Stock and the Option Stock (if the option granted by Section 3(c) hereof shall
have been exercised not later than 7:00 A.M., San Francisco time, on the date
two business days preceding the Closing Date), and payment therefor, shall be
made at the office of Heller Ehrman White & McAuliffe, at 7:00 a.m., San
Francisco time, on the fourth business day after the date of this Agreement, or
at such time on such other day, not later than seven full business days after
such fourth business day, as shall be agreed upon in writing by the Company, the
Selling Securityholders and you.  The date and hour of such delivery and payment
(which may be postponed as provided in Section 3(b) hereof) are herein called
the Closing Date.

              (b)    If the option granted by Section 3(c) hereof shall be
exercised after 7:00 a.m., San Francisco time, on the date two business days
preceding the Closing Date, delivery of certificates for the shares of Option
Stock, and payment therefor, shall be made at the office of Heller Ehrman White
& McAuliffe, at 7:00 a.m., San Francisco time, on the third business day after
the exercise of such option.

              (c)    Payment for the Stock purchased from the Company shall be
made to the Company or its order and payment for the Stock purchased from the
Selling Securityholders shall be made to the Custodian, for the account of the
Selling Securityholders, in each case by wire transfer of immediately available
funds.  Such payment shall be made upon delivery of certificates for the Stock
to you for the respective accounts of the several Underwriters against receipt
therefor signed by you.  Certificates for the Stock to be delivered to you shall
be registered in such name or names and shall be in such denominations as you
may request at least one business day before the Closing Date, in the case of
Underwritten Stock, and at least one business day prior to the purchase thereof,
in the case of the Option Stock.  Such certificates will be made available to
the Underwriters for inspection, checking and packaging at the offices of Lewco
Securities Corporation, 2 Broadway, New York, New York 10004 on the business day
prior to the Closing Date or, in the case of the Option Stock, by 3:00 p.m., New
York time, on the business day preceding the date of purchase.

       It is understood that you, individually and not on behalf of the
Underwriters, may (but shall not be obligated to) make payment to the Company
and the Selling Securityholders for shares to be purchased by any Underwriter
whose check shall not have been received by you on the Closing Date or any later
date on which Option Stock is purchased for the account of such Underwriter.
Any such payment by you shall not relieve such Underwriter from any of its
obligations hereunder.

                                     8
<PAGE>

       6.     FURTHER AGREEMENTS OF THE COMPANY.  The Company covenants and
agrees as follows:

              (a)    The Company will (i) prepare and timely file with the
Commission under Rule 424(b) a Prospectus containing information previously
omitted at the time of effectiveness of the Registration Statement in reliance
on Rule 430A and (ii) not file any amendment to the Registration Statement or
supplement to the Prospectus of which you shall not previously have been advised
and furnished with a copy or to which you shall have reasonably objected in
writing or which is not in compliance with the Securities Act or the rules and
regulations of the Commission.

              (b)    The Company will promptly notify each Underwriter in the
event of (i) the request by the Commission for amendment of the Registration
Statement or for supplement to the Prospectus or for any additional information,
(ii) the issuance by the Commission of any stop order suspending the
effectiveness of the Registration Statement, (iii) the institution or notice of
intended institution of any action or proceeding for that purpose, (iv) the
receipt by the Company of any notification with respect to the suspension of the
qualification of the Stock for sale in any jurisdiction, or (v) the receipt by
it of notice of the initiation or threatening of any proceeding for such
purpose.  The Company will make every reasonable effort to prevent the issuance
of such a stop order and, if such an order shall at any time be issued, to
obtain the withdrawal thereof at the earliest possible moment.

              (c)    The Company will (i) on or before the Closing Date, deliver
to you a signed copy of the Registration Statement as originally filed and of
each amendment thereto filed prior to the time the Registration Statement
becomes effective and, promptly upon the filing thereof, a signed copy of each
post-effective amendment, if any, to the Registration Statement (together with,
in each case, all exhibits thereto unless previously furnished to you) and will
also deliver to you, for distribution to the Underwriters, a sufficient number
of additional conformed copies of each of the foregoing (but without exhibits)
so that one copy of each may be distributed to each Underwriter, (ii) as
promptly as possible deliver to you and send to the several Underwriters, at
such office or offices as you may designate, as many copies of the Prospectus as
you may reasonably request, and (iii) thereafter from time to time during the
period in which a prospectus is required by law to be delivered by an
Underwriter or dealer, likewise send to the Underwriters as many additional
copies of the Prospectus and as many copies of any supplement to the Prospectus
and of any amended prospectus, filed by the Company with the Commission, as you
may reasonably request for the purposes contemplated by the Securities Act.

              (d)    If at any time during the period in which a prospectus is
required by law to be delivered by an Underwriter or dealer any event relating
to or affecting the Company, or of which the Company shall be advised in writing
by you, shall occur as a result of which it is necessary, in the opinion of
counsel for the Company or of counsel for the Underwriters, to supplement or
amend the Prospectus in order to make the Prospectus not misleading in the light
of the circumstances existing at the time it is delivered to a purchaser of the
Stock, the Company will forthwith prepare and file with the Commission a
supplement to the Prospectus or an amended prospectus so that the Prospectus as
so supplemented or amended will not contain any untrue statement of a material
fact or omit to state any material fact necessary in order to make the
statements therein, in the light of the circumstances existing at the time such
Prospectus is delivered to such purchaser, not misleading.  If, after the public
offering of the Stock by the Underwriters and during such period, the
Underwriters shall propose to vary the terms of offering thereof by reason of
changes in general market conditions or otherwise, you will advise the Company
in writing of the proposed variation, and, if in the opinion either of counsel
for the Company or of counsel for the Underwriters such proposed variation
requires that the Prospectus be supplemented or amended, the Company will
forthwith prepare and file with the Commission a supplement to the Prospectus or
an amended prospectus setting forth such variation.  The Company authorizes the
Underwriters and all dealers to whom any of the Stock may be sold by the several
Underwriters to use the Prospectus, as from time to time amended or
supplemented, in connection with the sale of the Stock in accordance with the
applicable provisions of the Securities Act and the applicable rules and
regulations thereunder for such period.

              (e)    Prior to the filing thereof with the Commission, the
Company will submit to you, for your information, a copy of any post-effective
amendment to the Registration Statement and any supplement to the Prospectus or
any amended prospectus proposed to be filed.

              (f)    The Company will cooperate, when and as requested by you,
in the qualification of the Stock for offer and sale under the securities or
blue sky laws of such jurisdictions as you may designate and, during

                                     9
<PAGE>

the period in which a prospectus is required by law to be delivered by an
Underwriter or dealer, in keeping such qualifications in good standing under
said securities or blue sky laws; PROVIDED, HOWEVER, that the Company shall
not be obligated to file any general consent to service of process or to
qualify as a foreign corporation in any jurisdiction in which it is not so
qualified.  The Company will, from time to time, prepare and file such
statements, reports, and other documents as are or may be required to continue
such qualifications in effect for so long a period as you may reasonably
request for distribution of the Stock.

              (g)    During a period of five years commencing with the date
hereof, the Company will furnish to you, and to each Underwriter who may so
request in writing, copies of all periodic and special reports furnished to
shareholders of the Company and of all information, documents and reports filed
with the Commission.

              (h)    Not later than the 45th day following the end of the fiscal
quarter first occurring after the first anniversary of the Effective Date, the
Company will make generally available to its security holders an earnings
statement in accordance with Section 11(a) of the Securities Act and Rule 158
thereunder.

              (i)    The Company agrees to pay all costs and expenses incident
to the performance of the  obligations of the Company and the Selling
Securityholders under this Agreement, including all costs and expenses incident
to (i) the preparation, printing and filing with the Commission and the National
Association of Securities Dealers, Inc. ("NASD") of the Registration Statement,
any Preliminary Prospectus and the Prospectus, (ii) the furnishing to the
Underwriters of copies of any Preliminary Prospectus and of the several
documents required by paragraph (c) of this Section 6 to be so furnished,
(iii) the printing of this Agreement and related documents delivered to the
Underwriters, (iv) the preparation, printing and filing of all supplements and
amendments to the Prospectus referred to in paragraph (d) of this Section 6,
(v) the furnishing to you and the Underwriters of the reports and information
referred to in paragraph (g) of this Section 6 and (vi) the printing and
issuance of stock certificates, including the transfer agent's fees.  The
Selling Securityholders will pay any transfer taxes incident to the transfer to
the Underwriters of the shares of Stock being sold by the Selling
Securityholders.

              (j)    The Company agrees to reimburse you, for the account of the
several Underwriters, for blue sky fees and related disbursements (including
counsel fees and disbursements and cost of printing memoranda for the
Underwriters) paid by or for the account of the Underwriters or their counsel in
qualifying the Stock under state securities or blue sky laws and in the review
of the offering by the NASD.

              (k)    The Company hereby agrees that, without the prior written
consent of Hambrecht & Quist LLC on behalf of the Underwriters, the Company will
not, for a period of 90 days following the effective date of the Registration
Statement, directly or indirectly, sell, offer, contract to sell, transfer the
economic risk of ownership in, make any short sale, pledge or otherwise dispose
of any shares of Common Stock or any securities convertible into or exchangeable
or exercisable for or any rights to purchase or acquire Common Stock.  The
foregoing sentence shall not apply to (A) the Stock to be sold to the
Underwriters pursuant to this Agreement, (B) Common Stock or options to purchase
Common Stock or other equity incentives granted under the Option Plans,
(C) shares of Common Stock issued by the Company upon the exercise of options
granted under the Option Plans or upon the exercise of warrants outstanding as
of the date hereof, and (D) capital stock issued in connection with acquisitions
or strategic alliances entered into by the Company, provided that the Company
shall notify Hambrecht & Quist LLC of such proposed acquisitions at least five
(5) business days prior to entering into a legally binding letter of intent or
a definitive agreement with respect to such acquisitions.

              (l)    If at any time during the 25-day period after the
Registration Statement becomes effective any rumor, publication or event
relating to or affecting the Company shall occur as a result of which in your
opinion the market price for the Stock has been or is likely to be materially
affected (regardless of whether such rumor, publication or event necessitates a
supplement to or amendment of the Prospectus), the Company will, after written
notice from you advising the Company to the effect set forth above, forthwith
prepare, consult with you concerning the substance of, and disseminate a press
release or other public statement, reasonably satisfactory to you, responding to
or commenting on such rumor, publication or event.

              (m)    The Company is familiar with the Investment Company Act of
1940, as amended, and has in the past conducted its affairs, and will in the
future conduct its affairs, in such a manner to ensure that the Company was not
and will not be an "investment company" or a company "controlled" by an
"investment

                                     10
<PAGE>

company" within the meaning of the Investment Company Act of 1940, as amended,
and the rules and regulations thereunder.

       7.     INDEMNIFICATION AND CONTRIBUTION.

              (a)    The Company agrees to indemnify and hold harmless each
Underwriter and each person (including each partner or officer thereof) who
controls any Underwriter within the meaning of Section 15 of the Securities Act
from and against any and all losses, claims, damages or liabilities, joint or
several, to which such indemnified parties or any of them may become subject
under the Securities Act, the Securities Exchange Act of 1934, as amended
(herein called the Exchange Act), or the common law or otherwise, and the
Company agrees to reimburse each such Underwriter and controlling person for any
legal or other expenses (including, except as otherwise hereinafter provided,
reasonable fees and disbursements of counsel) incurred by the respective
indemnified parties in connection with defending against any such losses,
claims, damages or liabilities or in connection with any investigation or
inquiry of, or other proceeding which may be brought against, the respective
indemnified parties, in each case arising out of or based upon (i) any untrue
statement or alleged untrue statement of a material fact contained in the
Registration Statement (including the Prospectus as part thereof and any
Rule 462(b) registration statement) or any post-effective amendment thereto
(including any Rule 462(b) registration statement), or the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, or (ii) any untrue
statement or alleged untrue statement of a material fact contained in any
Preliminary Prospectus or the Prospectus (as amended or as supplemented if the
Company shall have filed with the Commission any amendment thereof or supplement
thereto) or the omission or alleged omission to state therein a material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading; PROVIDED, HOWEVER,
that (1) the indemnity agreements of the Company contained in this paragraph (a)
shall not apply to any such losses, claims, damages, liabilities or expenses if
such statement or omission was made in reliance upon and in conformity with
information furnished as herein stated or otherwise furnished in writing to the
Company by or on behalf of any Underwriter for use in any Preliminary Prospectus
or the Registration Statement or the Prospectus or any such amendment thereof or
supplement thereto and (2) the indemnity agreement contained in this
paragraph (a) with respect to any Preliminary Prospectus shall not inure to the
benefit of any Underwriter from whom the person asserting any such losses,
claims, damages, liabilities or expenses purchased the Stock which is the
subject thereof (or to the benefit of any person controlling such Underwriter)
if at or prior to the written confirmation of the sale of such Stock a copy of
the Prospectus (or the Prospectus as amended or supplemented) was not sent or
delivered to such person and the untrue statement or omission of a material fact
contained in such Preliminary Prospectus was corrected in the Prospectus (or the
Prospectus as amended or supplemented) unless the failure is the result of
noncompliance by the Company with paragraph (c) of Section 6 hereof.  The
indemnity agreements of the Company contained in this paragraph (a) and the
representations and warranties of the Company contained in Section 2 hereof
shall remain operative and in full force and effect regardless of any
investigation made by or on behalf of any indemnified party and shall survive
the delivery of and payment for the Stock.

              (b)    Subject to the provisions of paragraph (g) of this
Section 7, the Selling Securityholders severally and not jointly agree to
indemnify and hold harmless each Underwriter and each person (including each
partner or officer thereof) who controls any Underwriter within the meaning of
Section 15 of the Securities Act from and against any and all losses, claims,
damages or liabilities, joint or several, to which such indemnified parties or
any of them may become subject under the Securities Act, the Exchange Act or the
common law or otherwise, and the Selling Securityholders severally and not
jointly agree to reimburse each such Underwriter and each person (including each
partner or officer thereof) who controls any Underwriter within the meaning of
Section 15 of the Securities Act for any legal or other expenses (including,
except as otherwise hereinafter provided, reasonable fees and disbursements of
counsel) incurred by the respective indemnified parties in connection with
defending against any such losses, claims, damages or liabilities or in
connection with any investigation or inquiry of, or other proceeding which may
be brought against, the respective indemnified parties, in each case arising out
of or based upon (i) information pertaining to such Selling Securityholder
furnished by or on behalf of such Selling Securityholder expressly for use in
any Preliminary Prospectus or the Registration Statement or the Prospectus or
any such amendment thereof or supplement thereto, (ii) facts that would
constitute a breach of any representation or warranty of such Selling
Securityholder set forth in Section 2(b) hereof, or (iii) in the case of an
Affiliated Selling Securityholder, facts that would constitute a breach of any
representation or warranty of such Affiliated Selling Securityholder set forth
in Section 2(c) hereof. The indemnity agreements of the Selling Securityholders
contained in this paragraph (b) and the representations and warranties of the
Selling Securityholders contained

                                     11
<PAGE>

in Section 2 hereof shall remain operative and in full force and effect
regardless of any investigation made by or on behalf of any indemnified party
and shall survive the delivery of and payment for the Stock.

              (c)    Each Underwriter severally agrees to indemnify and hold
harmless the Company and the Selling Securityholders, each of its officers who
signs the Registration Statement on his own behalf or pursuant to a power of
attorney, each of its directors, each other Underwriter and each person
(including each partner or officer thereof) who controls the Company or any such
other Underwriter within the meaning of Section 15 of the Securities Act and the
Selling Securityholders, from and against any and all losses, claims, damages or
liabilities, joint or several, to which such indemnified parties or any of them
may become subject under the Securities Act, the Exchange Act, or the common law
or otherwise and to reimburse each of them for any legal or other expenses
(including, except as otherwise hereinafter provided, reasonable fees and
disbursements of counsel) incurred by the respective indemnified parties in
connection with defending against any such losses, claims, damages or
liabilities or in connection with any investigation or inquiry of, or other
proceeding which may be brought against, the respective indemnified parties, in
each case arising out of or based upon (i) any untrue statement or alleged
untrue statement of a material fact contained in the Registration Statement
(including the Prospectus as part thereof and any Rule 462(b) registration
statement) or any post-effective amendment thereto (including any Rule 462(b)
registration statement) or the omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading or (ii) any untrue statement or alleged untrue statement
of a material fact contained in the Prospectus (as amended or as supplemented if
the Company shall have filed with the Commission any amendment thereof or
supplement thereto) or the omission or alleged omission to state therein a
material fact necessary in order to make the statements therein, in the light of
the circumstances under which they were made, not misleading, if such statement
or omission was made in reliance upon and in conformity with information
furnished as herein stated or otherwise furnished in writing to the Company by
or on behalf of such indemnifying Underwriter for use in the Registration
Statement or the Prospectus or any such amendment thereof or supplement thereto.
The indemnity agreement of each Underwriter contained in this paragraph (c)
shall remain operative and in full force and effect regardless of any
investigation made by or on behalf of any indemnified party and shall survive
the delivery of and payment for the Stock.

              (d)    Each party indemnified under the provisions of
paragraphs (a), (b) and (c) of this Section 7 agrees that, upon the service of a
summons or other initial legal process upon it in any action or suit instituted
against it or upon its receipt of written notification of the commencement of
any investigation or inquiry of, or proceeding against, it in respect of which
indemnity may be sought on account of any indemnity agreement contained in such
paragraphs, it will promptly give written notice (herein called the Notice) of
such service or notification to the party or parties from whom indemnification
may be sought hereunder.  No indemnification provided for in such paragraphs
shall be available to any party who shall fail so to give the Notice if the
party to whom such Notice was not given was unaware of the action, suit,
investigation, inquiry or proceeding to which the Notice would have related and
was prejudiced by the failure to give the Notice, but the omission so to notify
such indemnifying party or parties of any such service or notification shall not
relieve such indemnifying party or parties from any liability which it or they
may have to the indemnified party for contribution or otherwise than on account
of such indemnity agreement.  Any indemnifying party shall be entitled at its
own expense to participate in the defense of any action, suit or proceeding
against, or investigation or inquiry of, an indemnified party.  Any indemnifying
party shall be entitled, if it so elects within a reasonable time after receipt
of the Notice by giving written notice (herein called the Notice of Defense) to
the indemnified party, to assume (alone or in conjunction with any other
indemnifying party or parties) the entire defense of such action, suit,
investigation, inquiry or proceeding, in which event such defense shall be
conducted, at the expense of the indemnifying party or parties, by counsel
chosen by such indemnifying party or parties and reasonably satisfactory to the
indemnified party or parties; PROVIDED, HOWEVER, that (i) if the indemnified
party or parties reasonably determine that there may be a conflict between the
positions of the indemnifying party or parties and of the indemnified party or
parties in conducting the defense of such action, suit, investigation, inquiry
or proceeding or that there may be legal defenses available to such indemnified
party or parties different from or in addition to those available to the
indemnifying party or parties, then counsel for the indemnified party or parties
shall be entitled to conduct the defense to the extent reasonably determined by
such counsel to be necessary to protect the interests of the indemnified party
or parties and (ii) in any event, the indemnified party or parties shall be
entitled to have counsel chosen by such indemnified party or parties participate
in, but not conduct, the defense.  If, within a reasonable time after receipt of
the Notice, an indemnifying party gives a Notice of Defense and the counsel
chosen by the indemnifying party or parties is reasonably

                                     12
<PAGE>

satisfactory to the indemnified party or parties, the indemnifying party or
parties will not be liable under paragraphs (a) through (d) of this Section 7
for any legal or other expenses subsequently incurred by the indemnified party
or parties in connection with the defense of the action, suit, investigation,
inquiry or proceeding, except that (A) the indemnifying party or parties shall
bear the legal and other expenses incurred in connection with the conduct of
the defense as referred to in clause (i) of the proviso to the preceding
sentence and (B) the indemnifying party or parties shall bear such other
expenses as it or they have authorized to be incurred by the indemnified party
or parties. If, within a reasonable time after receipt of the Notice, no
Notice of Defense has been given, the indemnifying party or parties shall be
responsible for any legal or other expenses incurred by the indemnified party
or parties in connection with the defense of the action, suit, investigation,
inquiry or proceeding.

              (e)    If the indemnification provided for in this Section 7 is
unavailable or insufficient to hold harmless an indemnified party under
paragraph (a), (b) or (c) of this Section 7, then each indemnifying party, in
lieu of indemnifying such indemnified party, shall contribute to the amount paid
or payable by such indemnified party as a result of the losses, claims, damages
or liabilities referred to in paragraph (a), (b) or (c) of this Section 7 (i) in
such proportion as is appropriate to reflect the relative benefits received by
each indemnifying party from the offering of the Stock or (ii) if the allocation
provided by clause (i) above is not permitted by applicable law, in such
proportion as is appropriate to reflect not only the relative benefits referred
to in clause (i) above but also the relative fault of each indemnifying party in
connection with the statements or omissions that resulted in such losses,
claims, damages or liabilities, or actions in respect thereof, as well as any
other relevant equitable considerations.  The relative benefits received by the
Company and the Selling Securityholders on the one hand and the Underwriters on
the other shall be deemed to be in the same respective proportions as the total
net proceeds from the offering of the Stock received by the Company and the
Selling Securityholders and the total underwriting discount received by the
Underwriters, as set forth in the table on the cover page of the Prospectus,
bear to the aggregate public offering price of the Stock.  Relative fault shall
be determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to state
a material fact relates to information supplied by each indemnifying party and
the parties' relative intent, knowledge, access to information and opportunity
to correct or prevent such untrue statement or omission.

       The parties agree that it would not be just and equitable if
contributions pursuant to this paragraph (e) were to be determined by pro rata
allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation which does not take into account
the equitable considerations referred to in the first sentence of this
paragraph (e).  The amount paid by an indemnified party as a result of the
losses, claims, damages or liabilities, or actions in respect thereof, referred
to in the first sentence of this paragraph (e) shall be deemed to include any
legal or other expenses reasonably incurred by such indemnified party in
connection with investigation, preparing to defend or defending against any
action or claim which is the subject of this paragraph (e). Notwithstanding the
provisions of this paragraph (e), no Underwriter shall be required to contribute
any amount in excess of the underwriting discount applicable to the Stock
purchased by such Underwriter. No person guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation.  The Underwriters' obligations in this paragraph (e) to
contribute are several in proportion to their respective underwriting
obligations and not joint.

       Each party entitled to contribution agrees that upon the service of a
summons or other initial legal process upon it in any action instituted against
it in respect of which contribution may be sought, it will promptly give written
notice of such service to the party or parties from whom contribution may be
sought, but the omission so to notify such party or parties of any such service
shall not relieve the party from whom contribution may be sought from any
obligation it may have hereunder or otherwise (except as specifically provided
in paragraph (d) of this Section 7).

              (f)    Neither the Company nor the Selling Securityholders will,
without the prior written consent of each Underwriter, settle or compromise or
consent to the entry of any judgment in any pending or threatened claim, action,
suit or proceeding in respect of which indemnification may be sought hereunder
(whether or not such Underwriter or any person who controls such Underwriter
within the meaning of Section 15 of the Securities Act or Section 20 of the
Exchange Act is a party to such claim, action, suit or proceeding) unless such
settlement, compromise or consent includes an unconditional release of such
Underwriter and each such controlling person from all liability arising out of
such claim, action, suit or proceeding.

                                     13
<PAGE>

              (g)    The liability of each Selling Securityholder under such
Selling Securityholder's representations and warranties contained in
paragraphs (b) and (c) of Section 2 hereof and under the indemnity and
reimbursement agreements contained in the provisions of this Section 7 hereof
shall be limited to an amount equal to the public offering price of the stock
sold by such Selling Securityholder to the Underwriters.  In addition, no
Selling Securityholder shall be liable under the indemnity and reimbursement
agreements of Section 7 hereof unless and until the Underwriters have made
written demand on the Company for payment under such Section which shall not
have been paid or agreed to be paid by the Company within 45 days after receipt
by the Company of such demand.  A copy of such demand when made to the Company
shall be provided to the Selling Securityholders.  The Company and the Selling
Securityholders may agree, as among themselves and without limiting the rights
of the Underwriters under this Agreement, as to the respective amounts of such
liability for which they each shall be responsible.

       8.     TERMINATION.  This Agreement may be terminated by you at any time
prior to the Closing Date by giving written notice to the Company and the
Selling Securityholders if after the date of this Agreement trading in the
Common Stock shall have been suspended, or if there shall have occurred (i) the
engagement in hostilities or an escalation of major hostilities by the United
States or the declaration of war or a national emergency by the United States on
or after the date hereof, (ii) any outbreak of hostilities or other national or
international calamity or crisis or change in economic or political conditions
if the effect of such outbreak, calamity, crisis or change in economic or
political conditions in the financial markets of the United States would, in the
Underwriters' reasonable judgment, make the offering or delivery of the Stock
impracticable, (iii) suspension of trading in securities generally or a material
adverse decline in value of securities generally on the New York Stock Exchange,
the American Stock Exchange, The Nasdaq Stock Market, or limitations on prices
(other than limitations on hours or numbers of days of trading) for securities
on either such exchange or system, (iv) the enactment, publication, decree or
other promulgation of any federal or state statute, regulation, rule or order
of, or commencement of any proceeding or investigation by, any court,
legislative body, agency or other governmental authority which in the
Underwriters' reasonable opinion materially and adversely affects or will
materially or adversely affect the business or operations of the Company,
(v) declaration of a banking moratorium by either federal or New York State
authorities or (vi) the taking of any action by any federal, state or local
government or agency in respect of its monetary or fiscal affairs which in the
Underwriters' reasonable opinion has a material adverse effect on the securities
markets in the United States.  If this Agreement shall be terminated pursuant to
this Section 8, there shall be no liability of the Company or the Selling
Securityholders to the Underwriters and no liability of the Underwriters to the
Company or the Selling Securityholders; PROVIDED, HOWEVER, that in the event of
any such termination the Company and the Selling Securityholders agree to
indemnify and hold harmless the Underwriters from all costs or expenses incident
to the performance of the obligations of the Company and the Selling
Securityholders under this Agreement, including all costs and expenses referred
to in paragraphs (i) and (j) of Section 6 hereof.

       9.     CONDITIONS OF UNDERWRITERS' OBLIGATIONS.  The obligations of the
several Underwriters to purchase and pay for the Stock shall be subject to the
performance by the Company and by the Selling Securityholders of all their
respective obligations to be performed hereunder at or prior to the Closing Date
or any later date on which Option Stock is to be purchased, as the case may be,
and to the following further conditions:

              (a)    The Registration Statement shall have become effective; and
no stop order suspending the effectiveness thereof shall have been issued and no
proceedings therefor shall be pending or threatened by the Commission.

              (b)    The legality and sufficiency of the sale of the Stock
hereunder and the validity and form of the certificates representing the Stock,
all corporate proceedings and other legal matters incident to the foregoing, and
the form of the Registration Statement and of the Prospectus (except as to the
financial statements contained therein), shall have been approved at or prior to
the Closing Date by Gunderson Dettmer Stough Villeneuve Franklin &
Hachigian, LLP, counsel for the Underwriters.

              (c)    You shall have received from Heller Ehrman White &
McAuliffe, counsel for the Company and each of the Affiliated Selling
Securityholders, an opinion, addressed to the Underwriters and dated the
Closing Date, covering the matters set forth in Annex A hereto, and if Option
Stock is purchased at any date after the Closing Date, an additional opinion
from such counsel, addressed to the Underwriters and dated such

                                     14
<PAGE>

later date, confirming that the statements expressed as of the Closing Date in
such opinion remain valid as of such later date.

              (d)    You shall have received from [___________________], counsel
for [___________________], an opinion, addressed to the Underwriters and dated
the Closing Date, covering the matters set forth in Annex B hereto.

              (e)    You shall have received from Jim Jantos, counsel for
Brittania Holdings Limited, an opinion, addressed to the Underwriters and dated
the date on which Option Stock is purchased covering the matters set forth in
Annex C hereto.

              (f)    You shall be satisfied that (i) as of the Effective Date,
the statements made in the Registration Statement and the Prospectus were true
and correct and neither the Registration Statement nor the Prospectus omitted to
state any material fact required to be stated therein or necessary in order to
make the statements therein, respectively, not misleading, (ii) since the
Effective Date, no event has occurred which should have been set forth in a
supplement or amendment to the Prospectus which has not been set forth in such a
supplement or amendment, (iii) since the respective dates as of which
information is given in the Registration Statement in the form in which it
originally became effective and the Prospectus contained therein, there has not
been any material adverse change or any development involving a prospective
material adverse change in or affecting the business, properties, financial
condition or results of operations of the Company, whether or not arising from
transactions in the ordinary course of business, and, since such dates, except
in the ordinary course of business, Company has not entered into any material
transaction not referred to in the Registration Statement in the form in which
it originally became effective and the Prospectus contained therein, (iv) the
Company does not have any material contingent obligations which are not
disclosed in the Registration Statement and the Prospectus, (v) there are not
any pending or known threatened legal proceedings to which the Company is a
party or of which property of the Company is the subject which are material and
which are not disclosed in the Registration Statement and the Prospectus,
(vi) there are not any franchises, contracts, leases or other documents which
are required to be filed as exhibits to the Registration Statement which have
not been filed as required, (vii) the representations and warranties of the
Company herein are true and correct in all material respects as of the Closing
Date or any later date on which Option Stock is to be purchased, as the case may
be, and (viii) there has not been any material change in the market for
securities in general or in political, financial or economic conditions from
those reasonably foreseeable as to render it impracticable in your reasonable
judgment to make a public offering of the Stock, or a material adverse change in
market levels for securities in general (or those of companies in particular) or
financial or economic conditions which render it inadvisable to proceed.

              (g)    You shall have received on the Closing Date and on any
later date on which Option Stock is purchased a certificate, dated the Closing
Date or such later date, as the case may be, and signed by the President and the
Chief Financial Officer of the Company, stating that the respective signers of
said certificate have carefully examined the Registration Statement in the form
in which it originally became effective and the Prospectus contained therein and
any supplements or amendments thereto, and that the statements included in
clauses (i) through (vii) of paragraph (f) of this Section 9 are true and
correct.

              (h)    You shall have received from PricewaterhouseCoopers LLP, a
letter or letters, addressed to the Underwriters and dated the Closing Date and
any later date on which Option Stock is purchased, confirming that they are
independent public accountants with respect to the Company within the meaning of
the Securities Act and the applicable published rules and regulations thereunder
and based upon the procedures described in their letter delivered to you
concurrently with the execution of this Agreement (herein called the Original
Letter), but carried out to a date not more than three business days prior to
the Closing Date or such later date on which Option Stock is purchased
(i) confirming, to the extent true, that the statements and conclusions set
forth in the Original Letter are accurate as of the Closing Date or such later
date, as the case may be, and (ii) setting forth any revisions and additions to
the statements and conclusions set forth in the Original Letter which are
necessary to reflect any changes in the facts described in the Original Letter
since the date of the Original Letter or to reflect the availability of more
recent financial statements, data or information.  The letters shall not
disclose any change, or any development involving a prospective change, in or
affecting the business or properties of the Company which, in your sole
judgment, makes it impractical or inadvisable to proceed with the public
offering of the Stock or the purchase of the Option Stock as contemplated by the
Prospectus.

                                     15
<PAGE>

              (i)    You shall have received from PricewaterhouseCoopers LLP a
letter stating that their review of the Company's system of internal accounting
controls, to the extent they deemed necessary in establishing the scope of their
examination of the Company's financial statements as at June 30, 1999, did not
disclose any weakness in internal controls that they considered to be material
weaknesses.

              (j)    You shall have been furnished evidence in usual written or
telegraphic form from the appropriate authorities of the several jurisdictions,
or other evidence satisfactory to you, of the qualification referred to in
paragraph (f) of Section 6 hereof.

              (k)    Prior to the Closing Date, the Stock to be issued and sold
by the Company shall have been duly authorized for listing by the NNM upon
official notice of issuance.

       All the agreements, opinions, certificates and letters mentioned above or
elsewhere in this Agreement shall be deemed to be in compliance with the
provisions hereof only if Gunderson Dettmer Stough Villeneuve Franklin &
Hachigian, LLP, counsel for the Underwriters, shall be reasonably satisfied that
they comply in form and scope.

       In case any of the conditions specified in this Section 9 shall not be
fulfilled, this Agreement may be terminated by you by giving notice to the
Company.  Any such termination shall be without liability of the Company or
Selling Securityholders to the Underwriters and without liability of the
Underwriters to the Company or the Selling Securityholders; PROVIDED, HOWEVER,
that (i) in the event of such termination, the Company and the Selling
Securityholders agree to indemnify and hold harmless the Underwriters from all
costs or expenses incident to the performance of the obligations of the Company
and the Selling Securityholders under this Agreement, including all costs and
expenses referred to in paragraphs (i) and (j) of Section 6 hereof, and (ii) if
this Agreement is terminated by you because of any refusal, inability or failure
on the part of the Company or the Selling Securityholders to perform any
agreement herein, to fulfill any of the conditions herein, or to comply with any
provision hereof other than by reason of a default by any of the Underwriters,
the Company will reimburse the Underwriters severally upon demand for all out-
of-pocket expenses (including reasonable fees and disbursements of counsel) that
shall have been incurred by them in connection with the transactions
contemplated hereby.

       10.    CONDITIONS OF THE OBLIGATION OF THE COMPANY AND THE SELLING
SECURITYHOLDERS.  The obligation of the Company and the Selling Securityholders
to deliver the Stock shall be subject to the conditions that (a) the
Registration Statement shall have become effective and (b) no stop order
suspending the effectiveness thereof shall be in effect and no proceedings
therefor shall be pending or threatened by the Commission.

       In case either of the conditions specified in this Section 10 shall not
be fulfilled, this Agreement may be terminated by the Company and the Selling
Securityholders by giving notice to you.  Any such termination shall be without
liability of the Company and the Selling Securityholders to the Underwriters and
without liability of the Underwriters to the Company or the Selling
Securityholders; PROVIDED, HOWEVER, that in the event of any such termination
the Company and the Selling Securityholders jointly and severally agree to
indemnify and hold harmless the Underwriters from all costs or expenses incident
to the performance of the obligations of the Company and the Selling
Securityholders under this Agreement, including all costs and expenses referred
to in paragraphs (i) and (j) of Section 6 hereof.

       11.    REIMBURSEMENT OF CERTAIN EXPENSES.  In addition to its other
obligations under Section 7 of this Agreement, the Company hereby agrees to
reimburse on a quarterly basis the Underwriters for all reasonable legal and
other expenses incurred in connection with investigating or defending any claim,
action, investigation, inquiry or other proceeding arising out of or based upon
any statement or omission, or any alleged statement or omission, described in
paragraph (a) of Section 7 of this Agreement, notwithstanding the absence of a
judicial determination as

                                     16
<PAGE>

to the propriety and enforceability of the obligations under this Section 11
and the possibility that such payments might later be held to be improper;
PROVIDED, HOWEVER, that (i) to the extent any such payment is ultimately held
to be improper, the persons receiving such payments shall promptly refund them
and (ii) such persons shall provide to the Company, upon request, reasonable
assurances of their ability to effect any refund, when and if due.

       12.    PERSONS ENTITLED TO BENEFIT OF AGREEMENT.  This Agreement shall
inure to the benefit of the Company, the Selling Securityholders and the several
Underwriters and, with respect to the provisions of Section 7 hereof, the
several parties (in addition to the Company, the Selling Securityholders and the
several Underwriters) indemnified under the provisions of said Section 7, and
their respective personal representatives, successors and assigns. Nothing in
this Agreement is intended or shall be construed to give to any other person,
firm or corporation any legal or equitable remedy or claim under or in respect
of this Agreement or any provision herein contained.  The term "successors and
assigns" as herein used shall not include any purchaser, as such purchaser, of
any of the Stock from any of the several Underwriters.

       13.    NOTICES.  Except as otherwise provided herein, all communications
hereunder shall be in writing or by telegraph and, if to the Underwriters, shall
be mailed, telegraphed or delivered to Hambrecht & Quist LLC, One Bush Street,
San Francisco, California 94104; and if to the Company, shall be mailed,
telegraphed or delivered to it at its office, 200 First Avenue West, Suite 500,
Seattle, Washington 98119, Attention: Chief Financial Officer; and if to the
Selling Securityholders, shall be mailed, telegraphed or delivered to the
Selling Securityholders in care of F5 Networks, Inc., 200 First Avenue West,
Suite 500, Seattle, WA, 98119, Attention:  Chief Financial Officer.  All notices
given by telegraph shall be promptly confirmed by letter.

       14.    MISCELLANEOUS.  The reimbursement, indemnification and
contribution agreements contained in this Agreement and the representations,
warranties and covenants in this Agreement shall remain in full force and effect
regardless of (a) any termination of this Agreement, (b) any investigation made
by or on behalf of any Underwriter or controlling person thereof, or by or on
behalf of the Company or the Selling Securityholders or their respective
directors or officers, and (c) delivery and payment for the Stock under this
Agreement; PROVIDED, HOWEVER, that if this Agreement is terminated prior to the
Closing Date, the provision of paragraphs (k) and (l) of Section 6 hereof shall
be of no further force or effect.

       This Agreement may be executed in two or more counterparts, each of which
shall be deemed an original, but all of which together shall constitute one and
the same instrument.

       This Agreement shall be governed by, and construed in accordance with,
the laws of the State of California.

                                     17
<PAGE>

       Please sign and return to the Company and to the Selling Securityholders
in care of the Company the enclosed duplicates of this letter, whereupon this
letter will become a binding agreement among the Company, the Selling
Securityholders and the several Underwriters in accordance with its terms.

                                   Very truly yours,

                                   F5 NETWORKS, INC.



                                   By
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          President and Chief Executive Officer

                                   Michael D. Almquist

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   --------------------------------------------
                                   Jeffrey S. Hussey

                                   Brian R. Dixon

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Brett L. Helsel

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Steven Goldman

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                     18
<PAGE>

                                   Britannia Holdings Limited

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Menlo Ventures VII, L.P.

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Taylor Hussey Family Trust

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Becky Arnett Hussey

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Gerald W. Hussey and Helen J. Hussey

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Gary Pittman

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                   Joann M. Reiter

                                   By:
                                      -----------------------------------------
                                          Jeffrey S. Hussey
                                          Attorney-in-Fact

                                     19
<PAGE>

The foregoing Agreement is hereby confirmed

and accepted as of the date first above written.

HAMBRECHT & QUIST LLC
BANCBOSTON ROBERTSON STEPHENS INC
BEAR, STEARNS & CO. INC.
DAIN RAUSCHER WESSELS, a division of Dain Rauscher Incorporated


By
   ----------------------------------------------------
       Managing Director
       Acting on behalf of the several Underwriters,
       including themselves, named in Schedule I hereto







                                     20
<PAGE>

                                 SCHEDULE I

                                UNDERWRITERS

<TABLE>
<CAPTION>
                                                            NUMBER OF SHARES
UNDERWRITERS                                                 TO BE PURCHASED
- ------------                                                 ---------------
<S>                                                         <C>
Hambrecht & Quist L.L.C....................................

BancBoston Robertson Stephens, Inc.........................

Bear, Stearns & Co. Inc....................................

Dain Rauscher Wessels, a division of
  Dain Rauscher Incorporated...............................

       Total...............................................      500,000
</TABLE>



                                     S-1
<PAGE>

                                 SCHEDULE II
                       PRIMARY SELLING SECURITYHOLDERS

                                    PART A


<TABLE>
                                                      NUMBER OF
    NAME AND ADDRESS OF                                 SHARES
  SELLING SECURITYHOLDERS                             TO BE SOLD
  -----------------------                             ----------
<S>                                                   <C>
Jeffrey S. Hussey (1)
c/o F5 Networks, Inc.
200 First Avenue West, Suite 500
Seattle, WA  98119

Brian R. Dixon (1)
c/o F5 Networks, Inc.
200 First Avenue West, Suite 500
Seattle, WA  98119

Michael D. Almquist
2232 12th Avenue West
Seattle, Washington 98119

Brett L. Helsel (1)
c/o F5 Networks, Inc.
200 First Avenue West, Suite 500
Seattle, WA  98119

Steven Goldman (1)
c/o F5 Networks, Inc.
2000 First Avenue West, Suite 500
Seattle, WA  98119

Britannia Holdings Limited
P.O. Box 556
Main Street
Charlestown, Nevis

Menlo Ventures VII, L.P.

Taylor Hussey Family Trust

Becky Arnett Hussey

Gerald W. Hussey and Helen J. Hussey

Gary Pittman

Joann M. Reiter

 Total:                                                 1,500,000
</TABLE>

                                 ADDITIONAL
                          SELLING SECURITYHOLDERS

                                   PART B

<TABLE>
<CAPTION>
                                                        NUMBER OF
            NAME AND ADDRESS OF                           SHARES
    ADDITIONAL SELLING SECURITYHOLDERS                  TO BE SOLD
    ----------------------------------                  ----------
<S>                                                     <C>
Total:                                                    300,000
</TABLE>

- ---------------
(1)    Affiliated Selling Securityholder


<PAGE>

                  [Heller Ehrman White & McAuliffe Letterhead]








                                September 8, 1999









F5 Networks, Inc.
200 First Avenue West, Suite 500
Seattle, Washington  98119


Dear Ladies and Gentlemen:

         This opinion is delivered in our capacity as counsel to F5 Networks,
Inc., a Washington corporation (the "Company"), in connection with the
preparation and filing by the Company with the Securities and Exchange
Commission (the "Commission") of a Registration Statement on Form S-1 (the
"Registration Statement") relating to (i) the authorization and issuance of
500,000 shares of common stock, no par value, of the Company (the "Issuer
Shares") and (ii) the sale of 1,500,000 shares of the Company's common stock, no
par value (the "Selling Shareholder Shares") by certain shareholders of the
Company (the "Selling Shareholders"). The Issuer Shares and the Selling
Shareholder Shares will be sold pursuant to an underwriting agreement (the
"Underwriting Agreement") to be entered into between the Company (selling
shareholders) and Hambrecht & Quist LLC (the "Representative"), as
representative of the underwriters (the "Underwriters") listed on Schedule I to
the Underwriting Agreement.

                                       I.


<PAGE>

        We have assumed the authenticity of all records, documents and
instruments submitted to us as originals, the genuineness of all signatures, the
legal capacity of natural persons and the conformity to the originals of all
records, documents and instruments submitted to us as copies. We have based our
opinion upon our review of the following records, documents, instruments and
certificates:

        (a) The Registration Statement;

        (b) The form of the proposed Underwriting Agreement;

        (c) The Articles of Incorporation (including all amendments thereto and
            restatements thereof) of the Company certified by the Washington
            Secretary of State as of September 8, 1999, and certified to us by
            an officer of the Company as being complete and in full force and
            effect as of the date of this opinion;

        (d) The Bylaws of the Company (and all amendments thereto) certified to
            us by an officer of the Company as being complete and in full force
            and effect as of the date of this opinion;

        (e) A Certificate of Existence/Authorization relating to the Company
            issued by the Washington Secretary of State dated September 8, 1999;

        (f) Records of the corporate proceedings of the Company certified to us
            by an officer of the Company constituting all records of proceedings
            and actions of the Company's board of directors relating to the
            transactions contemplated by the Underwriting Agreement and the
            issuance of the Selling Shareholder Shares by the Company to the
            Selling Shareholders; and

        (g) Certificates of officers of the Company as to certain factual
            matters.

        We have also assumed that the Issuer Shares will be duly executed,
authenticated and delivered on behalf of the Company prior to their issuance
against the consideration therefor to be set forth in a supplement or
supplements to the prospectus constituting a part of the Registration Statement.
In addition, we have also assumed that the Registration Statement will have been
declared effective by the Securities and Exchange Commission prior to, and will
continue to be effective at the time of, the issuance of the Issuer Shares.

                                       II.

        This opinion is limited to the federal laws of the United States of
America and the corporate law of the State of Washington, and we disclaim any
opinion as to the laws of any other jurisdiction. We further disclaim any
opinion as to any statute, rule, regulation,


                                       2

<PAGE>

ordinance, order or other promulgation of any regional or local governmental
body or as to any related judicial or administrative opinion.

                                      III.

         Based upon the foregoing and our examination of such questions of law
as we have deemed necessary or appropriate for the purpose of our opinion, and
subject to the limitations and qualifications expressed below, it is our opinion
that:

         1.       When the Issuer Shares are sold to the Underwriters and paid
for pursuant to the terms of the Underwriting Agreement, the Issuer Shares will
be duly authorized, validly issued and fully paid and non-assessable.

         2.       The Selling Shareholder Shares are validly issued and
nonassessable.

                                       IV.

         We hereby consent to the filing of this opinion as an exhibit to, and
to the use of this opinion in connection with, the Registration Statement and to
the reference to this firm under the heading "Legal Matters" in the prospectus
constituting a part of the Registration Statement.

         This opinion is rendered to you and to purchasers of the Securities
offered by you pursuant to the Registration Statement and is solely for the
benefit of you and such purchasers. This opinion may not be relied upon by any
other person, firm, corporation or other entity without our prior written
consent. We disclaim any obligation to advise you of any change of law that
occurs, or any facts of which we become aware, after the date of this opinion.


                                             Very truly yours,

                                             HELLER EHRMAN WHITE & McAULIFFE
                                             /s/ Heller Ehrman White & McAuliffe


                                       3

<PAGE>
                                                              Exhibit 10-15


                            FOURTH AMENDMENT TO LEASE


         THIS FOURTH AMENDMENT TO LEASE is made this 2nd day of July 1999,
between First Avenue West Building L.L.C., a Washington Limited Liability
Company ("Landlord" herein) and F5 Networks, Inc., ("Tenant" herein) for the
premises located in the city of Seattle, County of King, State of Washington,
commonly known as Suite 500, First West Building, 200 First Avenue West.

                                    RECITALS

A.       Landlord and Tenant are parties to that certain lease dated October
9th, 1997, the First Amendment to Lease dated July 23rd, 1998, the Second
Amendment to Lease dated September 30, 1998, and the Third Amendment to Lease
dated January 6, 1999 (the "Lease" herein). The Lease is made a part hereof
as though set forth in full herein.

B.       Landlord and Tenant hereby express their mutual desire and intend to
amend by this writing those terms, covenants and conditions contained in "3.
RENT" and "Premises Rentable Area, tenant proportionate share and security
deposit" as shown on Lease Reference Page.

NOW, THEREFORE, as parties hereto, Landlord and Tenant Agree as follows:

AMENDMENTS:

1. Paragraph "3. RENT" shall as of August 1, 1999 be amended to hereinafter
additionally provide as follows:

<TABLE>
<CAPTION>

     PERIOD                    TERM                   RATE/RSF       ANNUAL RENT         MONTHLY RENT
     ------                    ----                   --------       -----------         ------------
<S>                 <C>                              <C>            <C>                 <C>
     Year 1         (08/01/99 through 02/29/00)        $18.24        $384,104.04          $32,008.67
     Year 2         (03/01/00 through 02/28/01)        $19.45        $409,421.04          $34,118.42
     Year 3         (03/01/01 through 02/28/02)        $22.43        $472,277.04          $39,356.42
     Year 4         (03/01/02 through 02/29/03)        $23.43        $493,329.96          $41,110.83
     Year 5         (03/01/03 through 02/28/04)        $24.43        $514,383.00          $42,865.25

</TABLE>

2.       "Premises Rentable Area" as shown on Lease Reference Page shall be
amended to reflect the additional suite 506 (2,385 RSF) as shown on Exhibit A
on the fifth floor plus the existing suites totaling the square footage of
21,053 effective August 1, 1999.

3.       "Tenant Proportionate Share" as shown on Lease Reference Page shall
be amended to reflect the expanded suite percentage of 33.42% effective
August 1, 1999.

4.       "Security Deposit" as shown on the lease Reference Page shall be
amended to reflect the addition of $17,490 to the existing security deposit
to total $166,978.74 as tenant security deposit for the amended lease.

INCORPORATION:

5.       Except as herein modified, all other terms and conditions of the
Lease between the parties above described are ratified and affirmed and shall
continue in full force and effect.

                                                                            1

<PAGE>


         The parties hereto have executed this Fourth Amendment to Lease on
the date specified below their respective signatures.

LANDLORD                                    TENANT

FIRST AVENUE WEST BUILDING L.L.C.           F5 NETWORKS, INC.
A WASHINGTON LIMITED LIABILITY CO.          A WASHINGTON CORPORATION



BY:                                         BY:
   ---------------------------------            -------------------------------
         Fred W. Hines, Jr.                            Jeffrey S. Hussey

ITS:  MANAGING AGENT                        ITS:  President and CEO

DATE:                                       DATE:
     -------------------------------             ------------------------------


                                            BY:
                                                 ------------------------------
                                                    Robert J. Chamberlain

                                            ITS:
                                                 ------------------------------

                                            DATE:
                                                  ------------------------------



STATE OF WASHINGTON        )
                           )       SS
COUNTY OF SNOHOMISH        )

         I certify that I know or have satisfactory evidence that Fred. W.
Hines, Jr. signed this instrument on oath, that he was authorized to execute
said instrument as the managing agent of First Avenue West Building L.L.C.
pursuant to the provisions of the Limited Liability Company and acknowledged
said instrument as the managing agent of the First Avenue West Building
L.L.C. to be the free and voluntary act of said Limited Liability Company for
the uses and purposes mentioned in said instrument

Date:
      ------------------------------------------



- ------------------------------------------------
Notary Public in and for the State of Washington
residing at
            ------------------------------------
Print Name
My appointment expires:
                        ------------------------

                                                                             2
<PAGE>




STATE OF WASHINGTON        )
                           )       SS
COUNTY OF KING             )

         On this _______ day of _______________________, 19____, personally
appeared before me JEFFREY S. HUSSEY, to me known to be the President and CEO
of F5 Networks, Inc., the corporation that executed the within and foregoing
instrument and acknowledged said instrument to be the free and voluntary act
and deed of said corporation, for the uses and proposed therein mentioned,
and on oath stated that he was authorized to execute said instrument on
behalf of said corporation.

         IN WITNESS WHEREOF, I have hereunto set my hand and affixed my
official seal the day and year first above written.

Date:
       -------------------------------------


- ------------------------------------------------
Notary Public in and for the State of Washington
residing at
            ------------------------------------
Print Name
My appointment expires:
                        ------------------------





STATE OF WASHINGTON        )
                           )       SS
COUNTY OF KING             )

         On this _______ day of _______________________, 19____, personally
appeared before me , to me known ROBERT J. CHAMBERLAIN to be the
_________________________ of F5 Networks, Inc., the corporation that executed
the within and foregoing instrument and acknowledged said instrument to be the
free and voluntary act and deed of said corporation, for the uses and proposed
therein mentioned, and on oath stated that he was authorized to execute said
instrument on behalf of said corporation.

         IN WITNESS WHEREOF, I have hereunto set my hand and affixed my official
seal the day and year first above written.


Date:
       -----------------------------------------


- ------------------------------------------------
Notary Public in and for the State of Washington
residing at
             -----------------------------------
Print Name
My appointment expires:
                       -------------------------

                                                                             3


<PAGE>
                                                           Exhibit 10-16


                            FIFTH AMENDMENT TO LEASE


         THIS FIFTH AMENDMENT TO LEASE is made this 5th day of July 1999,
between First Avenue West Building L.L.C., a Washington Limited Liability
Company ("Landlord" herein) and F5 Networks, Inc., ("Tenant" herein) for the
premises located in the city of Seattle, County of King, State of Washington,
commonly known as Suite 500, First West Building, 200 First Avenue West.

                                    RECITALS

A.       Landlord and Tenant are parties to that certain lease dated October
9th, 1997, the First Amendment to Lease dated July 23rd, 1998, the Second
Amendment to Lease dated September 30, 1998, the Third Amendment to Lease
dated January 6, 1999, and the Fourth Amendment to Lease dated July 2, 1999
(the "Lease" herein). The Lease is made a part hereof as though set forth in
full herein.

B.       Landlord and Tenant hereby express their mutual desire and intend to
amend by this writing those terms, covenants and conditions contained in "3.
RENT", "10. ASSIGNMENT AND SUBLETTING" and "Premises Rentable Area, tenant
proportionate share and security deposit" as shown on Lease Reference Page.

NOW, THEREFORE, as parties hereto, Landlord and Tenant Agree as follows:

AMENDMENTS:

1. Paragraph "3. RENT" shall as of August 15, 1999 be amended to hereinafter
additionally provide as follows:

<TABLE>
<CAPTION>

     PERIOD                    TERM                   RATE/RSF       ANNUAL RENT         MONTHLY RENT
     ------                    ----                   --------       -----------         ------------
<S>                 <C>                               <C>            <C>                  <C>
     Year 1         (08/15/99 through 02/29/00)        $18.63        $501,504.00          $41,792.00
     Year 2         (03/01/00 through 02/28/01)        $19.79        $532,691.04          $44,390.92
     Year 3         (03/01/01 through 02/28/02)        $22.34        $601,417.08          $50,118.09
     Year 4         (03/01/02 through 02/29/03)        $23.34        $628,339.92          $52,361.66
     Year 5         (03/01/03 through 02/28/04)        $24.34        $655,263.00          $54,605.25
     Year 6         (03/01/04 through 02/28/05)        $25.00        $146,750.04          $12,229.17
     Year 7         (03/01/05 through 08/14/05)        $26.00        $152,619.96          $12,718.33

</TABLE>


2.    "10. ASSIGNMENT AND SUBLETTING", with respect to the 5,870 square feet
      leased in the Fifth Amendment to Lease, Tenant shall not have the right
      to assign or pledge this Lease or to sublet the whole or any part of
      the Premises, whether voluntarily or by operation of law, or permit the
      use or occupancy of the Premises by anyone other than Tenant, or assign
      this Lease for security purposes, without the prior written consent of
      Landlord, whose consent will not be unreasonably withheld or delayed,
      and such restrictions shall be binding upon any assignee or subtenant
      to which Landlord has consented. In the event Tenant desires to sublet
      the Premises, or any portion thereof, or assign this Lease, Tenant
      shall give written notice thereof to Landlord at least ten (10) days
      prior to the proposed commencement date of such subletting or
      assignment, which notice shall set for the name of the proposed
      subtenant or assignee, the relevant terms of any sublease and copies of
      financial reports and other relevant financial information of the
      proposed subtenant or assignee.

                                                                             1

<PAGE>

The Tenant shall have the right to withdraw its request for consent to an
assignment to prevent premature termination of the Lease. Similarly, the
Tenant shall have the right to withdraw its request for approval of a
sublease to prevent the recapture of any of its Premises by the Landlord. The
Landlord's consent should not be required in connection with a corporate
merger, reorganization, public offering or other corporate restructuring. The
Landlord should have to exercise its right under this Article within ten (10)
days of the Tenant's notice. The Tenant's obligation to reimburse Landlord
for cost incurred in connection with review and approval of an assignment or
a sublease should be capped at $500.00.

In addition to Landlord's right to approve of any subtenant or assignee,
Landlord shall have the option, in its sole discretion, in the event of any
proposed subletting or assignment, to terminate this Lease, or in the case of
a proposed subletting of less than the entire Premises, to recapture the
portion of the Premises to sublet, as of the date the subletting or
assignment is to be effective. The option shall be exercised by Landlord's
giving Tenant written notice thereof within ten (10) days following
Landlord's receipt of Tenant's written notice as required above. If this
Lease shall be terminated with respect to the entire Premises, the Term shall
end on the date stated in Tenant's notice as the effective date of the
sublease or assignment as if that date had been originally fixed in this
Lease for the expiration of the Term. If Landlord recaptures only a portion
of the Premises, the rent during the unexpired Term shall abate,
proportionately, based on the rent as of the date immediately prior to such
recapture. Tenant shall, at Tenant's own cost and expense, discharge in full
any outstanding commission obligation on the part of Tenant with respect to
this Lease, and any commissions which may be due and owing as a result of any
proposed assignment or subletting. Consent by Landlord to any assignment or
subletting shall not include consent to the assignment or transferring of any
lease renewal option rights or space option rights of the Premises, special
privileges or extra services granted to Tenant by this Lease, or addendum or
amendment thereto or letter of agreement (and such options, rights,
privileges or services shall terminate upon such assignment), unless Landlord
specifically grants in writing such options, rights, privileges or services
to assignee or subtenant. Any sale, assignment, mortgage, transfer of this
Lease or subletting which does not comply with the provisions of this Article
shall be void.

In the event that Tenant sells, sublets, assigns, or transfers this Lease and
at any time receives periodic rent and/or other consideration which exceeds
that which Tenant would at that time be obligated to pay to Landlord, Tenant
shall pay to Landlord 100% (one hundred percent) of the gross increase in
such rent as such rent is received by Tenant and 100% (one hundred percent)
of any other consideration received by Tenant from such subtenant in
connection with such sublease or in the case of an assignment of this Lease
by Tenant, Landlord shall receive 100% (one hundred percent) of any
consideration paid to Tenant by such assignee in connection with such
assignment.

3. "Premises Rentable Area" as shown on Lease Reference Page shall be amended
to reflect the additional suite 200 (5,870 RSF) shown on Exhibit A on the
fifth floor plus the existing suites totaling the square footage of 26,923
effective August 15, 1999.

4. "Tenant Proportionate Share" as shown on Lease Reference Page shall be
amended to reflect the expanded suite percentage of 42.73% effective August
15, 1999.

5. "Security Deposit" as shown on the lease Reference Page shall be amended
to reflect the addition of $39,133.32 to the existing security deposit to
total $206,112.06 as tenant security deposit for the amended lease.

6. "Term" as shown on the reference page shall as of August 15, 1999, be
amended to hereinafter additionally provide as follows: "SIX (6) YEARS
COMMENCING THE SOONER OF OCCUPANCY OR AUGUST 15, 1999 ON THE 5,870 SQUARE
FEET ONLY ADDED BY THIS FIFTH AMENDMENT"

                                                                             2

<PAGE>

INCORPORATION:

7 Except as herein modified, all other terms and conditions of the Lease between
the parties above described are ratified and affirmed and shall continue in full
force and effect.

         The parties hereto have executed this Fifth Amendment to Lease on the
date specified below their respective signatures.

LANDLORD                                    TENANT

FIRST AVENUE WEST BUILDING L.L.C.           F5 NETWORKS, INC.
A WASHINGTON LIMITED LIABILITY CO.          A WASHINGTON CORPORATION



BY:                                         BY:
   -----------------------------------          -------------------------------
         Fred W. Hines, Jr.                          Jeffrey S. Hussey
ITS:     Managing Agent                     ITS:     President and CEO
DATE:                                       DATE:
      --------------------------------            -----------------------------

                                            BY:
                                                -------------------------------
                                                     Robert J. Chamberlain
                                            ITS:
                                                 ------------------------------
                                            DATE:
                                                 ------------------------------


                                                                             3
<PAGE>



STATE OF WASHINGTON        )
                           )       SS
COUNTY OF SNOHOMISH        )

         I certify that I know or have satisfactory evidence that FRED W.
HINES, JR. signed this instrument on oath, that he was authorized to execute
said instrument as the Managing Agent of FirstAvenue West Building L.L.C.
pursuant to the provisions of the Limited Liability Company and acknowledged
said instrument as the managing agent of the First Avenue West Building
L.L.C. to be the free and voluntary act of said Limited Liability Company for
the uses and purposes mentioned in said instrument

Date:
      ------------------------------------


- ------------------------------------------------
Notary Public in and for the State of Washington
residing at
            ------------------------------------
Print Name
My appointment expires:
                        ------------------------







STATE OF WASHINGTON        )
                           )       SS
COUNTY OF KING             )

         On this _______ day of _______________________, 19____, personally
appeared before me JEFFREY S. HUSSEY, to me known to be the President and CEO of
F5 Networks, Inc., the corporation that executed the within and foregoing
instrument and acknowledged said instrument to be the free and voluntary act and
deed of said corporation, for the uses and proposed therein mentioned, and on
oath stated that he was authorized to execute said instrument on behalf of said
corporation.

         IN WITNESS WHEREOF, I have hereunto set my hand and affixed my official
seal the day and year first above written.

Date:
      ------------------------------------


- ------------------------------------------------
Notary Public in and for the State of Washington
residing at
            ------------------------------------
Print Name
My appointment expires:
                        ------------------------



                                                                             4


<PAGE>


STATE OF WASHINGTON        )
                           )       SS
COUNTY OF KING             )

         On this _______ day of _______________________, 19____, personally
appeared before me ROBERT J. CHAMBERLAIN, to me known to be the
_________________________ of F5 Networks, Inc., the corporation that executed
the within and foregoing instrument and acknowledged said instrument to be the
free and voluntary act and deed of said corporation, for the uses and proposed
therein mentioned, and on oath stated that he was authorized to execute said
instrument on behalf of said corporation.

         IN WITNESS WHEREOF, I have hereunto set my hand and affixed my official
seal the day and year first above written.

Date:
      ------------------------------------


- ------------------------------------------------
Notary Public in and for the State of Washington
residing at
            ------------------------------------
Print Name
My appointment expires:
                        ------------------------


                                                                             5

<PAGE>



                                401 ELLIOTT WEST


                             OFFICE LEASE AGREEMENT


                                     BETWEEN


                              401 ELLIOTT WEST LLC





                                       AND




                                F5 NETWORKS, INC.



<PAGE>

1.   BASIC LEASE TERMS

     Section 1 represents a summary of the basic terms of this Office Space
Lease for 401 Elliott West.

<TABLE>
<CAPTION>
<S>       <C>                                         <C>
     a.   DATE OF LEASE:                              July 31, 1999

     b.   TENANT:                                     F5 Networks, Inc.

          ADDRESS OF LEASED PREMISES:                 401 Elliott Avenue West
                                                      Seattle, WA 98119

          ADDRESS FOR BILLING AND NOTICES:            Prior to Commencement Date:

                                                      200 First Avenue West, Suite 500
                                                      Seattle, WA 98119
                                                      Phone: (206) 505 0800
                                                      Fax:  (206) 505 0897
                                                      Attn: Joann Reiter, General Counsel

                                                      Same as above except the address
                                                      shall be the same as Premises after
                                                      commencement of the Lease.

     c.   LANDLORD:                                   401 Elliott West L.L.C.

          ADDRESS FOR NOTICES:                        c/o Koehler McFadyen & Company
                                                      1601 Fifth Avenue, Suite 2210
                                                      Seattle, WA  98101
                                                      Phone: (206) 682 2680
                                                      Fax:  (206) 467 5975
                                                      Attn: Steve Koehler

                                                      or such other place as
                                                      Landlord may from time to time
                                                      designate by notice to Tenant

     d.   PREMISES AREA:                              83,097 rentable square feet,
                                                      Floors 1 through 4 of Building Two

     e.   BUILDING AREA:                              84,808 rentable square feet
          TENANT'S PERCENTAGE OF BUILDING              97.98%

     f.   PROJECT AREA                                297,682 rentable square feet
          TENANT'S PERCENTAGE OF PROJECT:              27.91%

     g.   TERM OF LEASE:                              This Lease shall commence on July 1, 2000 or such
                                                      earlier or later date as is provided in Section 3 (the
                                                      "Commencement Date") and shall terminate on the last day
                                                      of the one hundredth and forty-fourth (144th) full
                                                      calendar month after the Commencement Date (the
                                                      "Expiration Date").

     h.   BASE MONTHLY RENT:                          $164,462.81

     i.   PARKING:                                    Initial Monthly Charge of $100.00 per month for
                                                      each Parking Permit.

                                                      Number of parking permits allocated to Tenant: 158
                                                      spaces.

     j.   RENT ADJUSTMENT(S):                         MONTHS            BASE MONTHLY RENT
                                                      ------            -----------------
                                                      61 - 72           $173,118.75
                                                      73 - 84           $176,581.13
                                                      85 - 96           $180,043.50
                                                      97 - 108          $183,505.88
                                                      109 - 144         $186,968.25

     k.   ADDITIONAL RENT - ESTIMATED INITIAL
          TENANT'S SHARE OF EXPENSES:                 $46,742.06 per month

                                       2
<PAGE>

     l.   SECURITY DEPOSIT:                           $2,500,000 in the form of a Letter of Credit as further
                                                      described in Section 6 and Exhibit H.

     m.   NON-REFUNDABLE CLEANING FEE                 N/A

     n.   PREPAID RENT                                N/A

     o.   TENANT'S USE OF PREMISES:                   General Purpose Office with, Shipping/Light
                                                      Manufacturing Facility & Storage Space on the First
                                                      Floor



     p.   BROKERS:                                    Douglas Hanafin, Washington Partners, Inc.
          TO BE PAID BY:                              Landlord

     q.   GUARANTOR(S):                               N/A

     r.   ADDITIONAL TERMS:                           Sections 29 to 42

     s.   EXHIBIT(S):                                 Exhibit A - The Premises
                                                      Exhibit B - The Building and the Project
                                                      Exhibit C - Building Shell and Core Outline Specifications
                                                      Exhibit D - Signage Criteria
                                                      Exhibit E - Janitorial Specifications
                                                      Exhibit F-  Tenant Work Letter
                                                      Exhibit G   Option Space Performance Criterion
                                                      Exhibit H   Form of Letter of Credit
</TABLE>







                                       3

<PAGE>

2.   PREMISES/COMMON AREAS/PROJECT.

     a.   PREMISES. Landlord leases to Tenant the premises described in
          Section 1 and in Exhibit A (the "Premises"), located in the
          Building described on Exhibit B. The Building is part of a larger,
          multi-building development shown on Exhibit B (the "Project", with
          the buildings collectively referred to as the "Buildings"). Upon
          completion of the Tenant Improvements to the Premises, Landlord
          shall cause the rentable square footage of the Premises to be
          measured by Landlord's architect using the BOMA American National
          Standard Institute Publication, ANSI Z65.1-1996 standards (the
          "Rentable Square Footage"), which measurement shall govern with
          respect to the Premises Area of Section 1(d). Tenant shall have the
          right to have a Washington-licensed surveyor approved by Landlord
          and jointly responsible to Landlord and Tenant verify the Premises
          Net Rentable Area determined by Landlord's Architect, if it does so
          within twenty (20) days after receipt of the notice from Landlord's
          Architect. If based on such verification Tenant disagrees with the
          Net Rentable Area determined by Landlord's Architect it shall
          advise Landlord and its Architect of the deviation within ten (10)
          days thereafter or be deemed to have accepted Landlord's
          Architect's determination. If Tenant gives a timely notification of
          disagreement, then the parties shall jointly select a
          Washington-licensed surveyor to review the calculations of
          Landlord's architect and the Tenant selected surveyor and make the
          determination of Premises Net Rentable Area, which determination
          shall be final and binding on the parties. Landlord shall cause
          each building within the Project to be similarly measured for the
          purposes of Sections 1(e) and 1(f) upon completion of the interior
          improvements of such building(s). Each building shall be deemed
          added to the Project for the purposes of such computation upon the
          completion of the Building Shell and Core improvements, as defined
          in Exhibit C, to such building and the computations of Section 1,
          if delayed pending final measurement of Rentable Square Footage,
          shall be deemed retroactive to such date.

     b.   COMMON AREAS. As used in this Lease, "Common Areas" shall mean all
          portions of the Project not leased or demised for lease to specific
          tenants. During the Lease Term, Tenant and its licensees, invitees,
          customers and employees shall have the non-exclusive right to use
          the public portions of the Common Areas, including all parking
          areas, landscaped areas, entrances, lobbies, elevators, stairs,
          corridors, and public restrooms in common with Landlord, other
          Project tenants and their respective licensees, invitees, customers
          and employees. Landlord shall be entitled to create limited Common
          Areas within specified Buildings for exclusive use of the tenants
          within such Buildings. Landlord shall at all times have exclusive
          control and management of the Common Areas and no diminution
          thereof shall be deemed a constructive or actual eviction or
          entitle Tenant to compensation or a reduction or abatement of rent.
          Landlord in its discretion may increase, decrease or change the
          number, locations and dimensions of any Common Areas and other
          improvements shown on Exhibit B, and/or designate such areas
          limited Common Areas assigned to particular buildings within the
          Project.

     c.   PROJECT. Landlord reserves the right in its sole discretion to
          modify or alter the configuration or number of buildings in the
          Project, so long as such modification or alteration does not
          materially modify or alter Tenant's Premises and provided only that
          upon such modification or alteration, the Project Area as set forth
          in Section 1(e) shall be adjusted to reflect such modification or
          alteration using the BOMA American National Standard Institute
          Publication, ANSI Z65.1-1996.

3.   TERM. The Commencement Date listed in Section 1 of this Lease represents
     an estimate of the actual Commencement Date. The actual Commencement
     Date shall be the first to occur of the following events: (i) the date
     Tenant has substantially commenced the use and occupancy of the Premises
     or any portion thereof for purposes other than completion of the Tenant
     Work (as defined in Exhibit F), or (ii) one hundred twenty (120) days
     (the "Tenant Work Period") after the Delivery Date as defined in Exhibit
     F. The scheduled Delivery Date is February 29, 2000. As used herein,
     "Unexcused Delay" means the failure to meet an applicable deadline when
     caused by delays other than Tenant Delay or Force Majeure. "Day(s) of
     Unexcused Delay" means the number of days of delay past the applicable
     deadline caused by Unexcused Delay (excluding the effect of Tenant Delay
     or Force Majeure).

     The Tenant Work Period shall be extended by the amount of any Unexcused
     Delay. If on September 1, 2000, as a result of Unexcused Delay either
     (w) the Tenant Work is not yet substantially complete or (x) Tenant
     cannot occupy the Premises because the condition of the Building Shell
     and Core prevents issuance of such building permit sign offs as are
     necessary for beneficial occupancy of the Premises, then in addition to
     any extension of the Tenant Work Period as specified above, Tenant shall
     receive a credit against Base Rent that first becomes due under this
     Lease, in an amount equal to one (1) day of Base Rent for each such Day
     of Unexcused Delay. If, on November 1, 2000, as a result of Unexcused
     Delay either (y) the Tenant Work is not yet substantially complete or
     (z) Tenant cannot occupy the Premises because the condition of the
     Building Shell and Core prevents issuance of such building permit sign
     offs as are necessary for beneficial occupancy of the Premises, and
     Landlord does not substantially complete the Building Shell and Core so
     that (subject to the completion of the Tenant Work), building permit
     sign offs can be issued allowing Tenant to use and occupy the Premises
     for its intended purposes within thirty (30) days after written notice
     from Tenant of Tenant's intention to terminate this Lease as provided in
     this sentence, then Tenant may terminate this Lease by written notice
     given to Landlord at any time after the end of such thirty (30) day
     period and prior to the date the Building Shell and Core is
     substantially complete. If the Commencement Date is later than the
     estimated Commencement Date specified in Section 1 above, then, except
     as otherwise provided in this Section 3, this Lease shall not be void or
     voidable and Landlord shall not be liable to Tenant for such delay.

                                       4

<PAGE>

     Following the Commencement Date, Landlord shall confirm such date to
     Tenant in writing. Any dispute between Landlord and Tenant with respect
     to the terms and application of this Section 3 and Exhibits C and F
     attached shall be subject to binding arbitration in accordance with
     Section 39 of this Lease. All provisions of this Lease, other than those
     relating to the commencement of the Lease Term, the payment of Base Rent
     and Additional Rent, shall become effective on the date Tenant or its
     contractor or employees are first present on the Premises for
     construction, installation, move-in or other purposes.

4.   RENT

     a.   BASE MONTHLY RENT. Tenant shall pay Landlord monthly base rent in
          the initial amount in Section 1 which shall be payable monthly in
          advance on the first day of each and every calendar month ("Base
          Monthly Rent") provided, however, the first month's Base Monthly
          Rent and Tenant's Share of Expenses, including any adjustments for
          Rent Abatement as described in Section 30 below, is due and payable
          upon the earlier occurrence of (a) February 1, 2000 or (b) the
          Commencement Date of Tenant's Premises.

          For purposes of Section 467 of the Internal Revenue Code, the
          parties to this Lease hereby agree to allocate the stated Rents,
          provided herein, to the periods which correspond to the actual Rent
          payments as provided under the terms and conditions of this
          agreement.

     b.   RENT ADJUSTMENT.

          1)   Base Monthly Rent shall be increased periodically to the amounts
               and at the times set forth in Section 1(j).

     c.   EXPENSES. The purpose of this Section 4(c) is to ensure that Tenant
          bears its proportionate share of all actual Expenses related to the
          use, maintenance, ownership, repair or replacement, and insurance
          of the Building in which the Premises is located and associated
          Common Areas. Accordingly, beginning on the date Tenant takes
          possession of the Premises, Tenant shall each month pay to Landlord
          one-twelfth (1/12) of Tenant's Share of Expenses related to the
          Building and Associated Common Areas. As used in this Lease,
          "Tenant's Share" shall mean the Premises Area, as defined in
          Section 1(d), divided by the Building Area, as defined in Section
          1(e), and "Tenant's Share of Expenses" shall mean total Expenses
          for the Building and associated Common Areas, multiplied by
          Tenant's Share, provided that Landlord may specially allocate
          individual expenses where and in the manner necessary, in
          Landlord's discretion, to appropriately reflect the consumption of
          the expense or service. For example where some but not all premises
          in the Building have HVAC, Landlord may reallocate Building
          Expenses for HVAC to all premises utilizing HVAC to be apportioned
          on a per square foot basis, or could allocate to each premises
          utilizing HVAC the cost of maintaining that space's individual
          unit. In the event the average occupancy level of the Building or
          the Project for any year is less than ninety five percent (95%),
          the actual Expenses for the Building or the Project for such year
          shall be proportionately adjusted to reflect those costs which
          Landlord estimates would have been incurred, had the Building or
          Project, as applicable, been ninety five percent (95%) occupied
          during such year, such that Tenant's Share of Expenses more
          accurately reflects Tenant's actual usage. The Building is part of
          a larger, multi-building project described on Exhibit B hereto. In
          the event any Expenses are billed on a multi-building basis,
          Tenant's Share of such Expenses shall be charged based on the ratio
          of the Premises Area, as defined in Section 1(d) divided by the
          Project Area, defined in Section 1(f). The intent of the parties is
          to make rental payable by Tenant and other tenants in the Project
          absolutely net to Landlord assuming at least 95% occupancy, except
          for items expressly excluded in Section 4(c)(1)(f).

          1)   EXPENSES DEFINED. The term "Expenses" shall mean all costs and
               expenses of the ownership, operation, maintenance, repair or
               replacement, and insurance of the Project (allocated on a
               building-by-building basis, to the extent so provided above),
               including without limitation, the following costs:

               (a)   All supplies, materials, labor, equipment, and utilities
                     used in or related to the operation and maintenance of
                     the Project,

               (b)   All maintenance, management, janitorial, legal,
                     accounting, insurance, and service agreement costs
                     related to the Project. If the Building is managed by an
                     affiliate of Landlord, building management fees in
                     excess of management fees charged by independent
                     property managers for comparable buildings in the
                     Building's geographic market area shall be excluded from
                     defined expenses.

               (c)   All maintenance, replacement and repair costs relating
                     to the areas within or around the Project, including,
                     without limitation, air conditioning systems, sidewalks,
                     landscaping, service areas, driveways, parking Areas
                     (including resurfacing and restriping parking areas),
                     walkways, building exteriors (including painting), signs
                     and directories, repairing and replacing roofs, walls,
                     etc. These costs may be included either based on actual
                     expenditures or the use of an accounting reserve based
                     on past cost experience for the Project.


                                       5

<PAGE>

               (d)   Amortization (along with reasonable financing charges)
                     of capital betterments made to the Project which may be
                     required by any government authority or which will
                     improve the operating efficiency of the Project
                     (provided, however, that the amount of such amortization
                     for improvements not mandated by government authority
                     shall not exceed in any year the amount of costs
                     reasonably determined by Landlord in its sole discretion
                     to have been saved by the expenditure either through the
                     reduction or minimization of increases which would have
                     otherwise occurred).

               (e)   Real Property Taxes including all taxes, assessments
                     (general and special) and other impositions or charges
                     which may be taxed, charged, levied, assessed or imposed
                     upon all or any portion of or in relation to the Project
                     or any portion thereof, any leasehold estate in the
                     Premises or measured by Rent from the Premises,
                     including any increase caused by the transfer, sale or
                     encumbrance of the Project or any portion thereof. "Real
                     Property Taxes" shall also include any form of
                     assessment, levy, penalty, charge or tax (other than
                     estate, inheritance, net income, or franchise taxes)
                     imposed by any authority having a direct or indirect
                     power to tax or charge, including, without limitation,
                     any city, county, state federal or any improvement or
                     other district, whether such tax is (1) determined by
                     the value of the Project or the Rent or other sums
                     payable under this Lease; (2) upon or with respect to
                     any legal or equitable interest of Landlord in the
                     Project or any part thereof; (3) upon this transaction
                     or any document to which Tenant is a party creating a
                     transfer in any interest in the Project, (4) in lieu of
                     or as a direct substitute in whole or in part of or in
                     addition to any real property taxes on the Project, (5)
                     based on any parking spaces or parking facilities
                     provided in the Project, or (6) in consideration for
                     services, such as police protection, fire protection,
                     street, sidewalk and roadway maintenance, refuse removal
                     or other services that may be provided by any
                     governmental or quasi-governmental agency from time to
                     time which were formerly provided without charge or with
                     less charge to property owners or occupants.

               (f)   Landlord agrees that Expenses as defined in Section 4(c)
                     shall not include the following: (i) the cost of any
                     special services rendered to individual tenants for
                     which a separate charge is billed; (ii) costs of capital
                     betterments except as provided in subsection 4(c)(1)(d)
                     above; (iii) Legal fees, brokerage commissions,
                     advertising costs, or other related expenses incurred by
                     Landlord in an effort to generate rental income; (iv)
                     Repairs, alterations, additions, improvements or
                     replacements made to rectify or correct any defect in
                     the original design, materials or workmanship of
                     Building or common areas (but not including repairs,
                     alterations, additions, improvements or replacements
                     made as a result of ordinary wear and tear); (v) Damage
                     and repairs attributable to fire or other casualty for
                     which Landlord is reimbursed from insurance proceeds;
                     (vi) (a) Executive Salaries or (b) Salaries of service
                     personnel for performance of services except to the
                     extent incurred directly in connection with the
                     management, operation, repair or maintenance of the
                     Building; (viii) Landlord's general overhead expenses
                     not related to the Building, provided that Landlord
                     shall be allowed to include the value of any rent-free
                     or rent-reduced occupancy in the Building if such is
                     given to the managing entity in lieu of a higher
                     management fee; (ix) Legal fees, accountants' fees and
                     other expenses incurred in connection with disputes with
                     tenants or other occupants of the Building or associated
                     with the enforcement of the terms of any leases with
                     other tenants or otherwise incurred for any reason other
                     than for the general benefit of all tenants in the
                     Building; (x) Costs (including permit, license and
                     inspection fees) incurred in renovating or otherwise
                     improving, decorating, painting or altering (a) vacant
                     space (excluding common areas) in the Building, or (b)
                     space for tenants or other occupants in the Building, or
                     (c) costs incurred in supplying any improvement item
                     specifically for, or specific services to, other tenants
                     in the Building; (xi) Principal and/or interest payments
                     called for under any debt secured by a mortgage or deed
                     of trust on the Building; (e) Landlord shall not attempt
                     to collect in excess of one hundred percent (100%) of
                     Operating Expenses and shall not recover any item of
                     cost more than once; (xiii) Any bad debt loss, rent
                     loss, or reserves for bad debts or rent loss; (xiv) All
                     items and services for which Tenant or any other tenant
                     in the Building otherwise reimburses Landlord; (xv)
                     Electric power costs for which any tenant directly
                     contracts with the local public service company; (xvi)
                     Costs arising from Landlord's political or charitable
                     contributions; (xvii) Costs, other than those incurred
                     in ordinary maintenance, for the purchase and
                     installation of sculpture, paintings or other objects of
                     art; (xviii) Tax penalties incurred as a result of
                     Landlord's negligence, inability or unwillingness to
                     make payments when due; (xix) Costs incurred due to a
                     violation by Landlord or any other tenant of the
                     Building of the terms and conditions of any lease; (xx)
                     Costs and expenses incurred in complying with hazardous
                     waste and environmental laws where the

                                       6

<PAGE>

                     lack of compliance is caused by hazardous waste brought
                     into the Project by Landlord, its employees, agents or
                     contractors or other tenants; (xxi) Costs or expenses
                     which would be capitalized under generally accepted
                     accounting principals, and which relate to the initial
                     completion of the Premises, load bearing walls and other
                     structural elements of the Building or the Project, or
                     during the initial Lease Term related to the replacement
                     of the heating and air conditioning and other Building
                     and Project systems; and (xxii) direct costs of managing
                     the Garage paid to third party garage operators such as
                     management fees, attendants, cashiers and maintenance of
                     ticket dispensing equipment.

          2)   ANNUAL ESTIMATE OF EXPENSES, TENANT'S SHARE. When Tenant takes
               possession of the Premises, Landlord shall estimate Tenant's
               share of Expenses for the remainder of the calendar year, and
               at the commencement of each calendar year thereafter, Landlord
               shall estimate Tenant's Share of Expenses for the coming year
               by multiplying the appropriate estimated annual Building or
               Project Expenses by Tenant's Share.

          3)   MONTHLY PAYMENT OF EXPENSES. Tenant shall pay to Landlord,
               monthly in advance, as Additional Rent, one-twelfth (1/12) of
               the Annual Estimate of Tenant's Share of Expenses beginning on
               the date Tenant takes possession of the Premises. As soon as
               practical following each calendar year, Landlord shall prepare
               an accounting of actual Expenses incurred during the prior
               calendar year and such accounting shall reflect Tenant's Share
               of Expenses. If the Additional Rent paid by Tenant under this
               Section 4(c)(3) during the preceding calendar year was less
               than the actual amount of Tenant's Share of Expenses, Landlord
               shall so notify Tenant and Tenant shall pay such amount to
               Landlord within 30 days of receipt of such notice. Such amount
               shall be deemed to have accrued during the prior calendar year
               and shall be due and payable from Tenant even though the term
               of this Lease has expired or this Lease has been terminated
               prior to Tenant's receipt of this notice. Tenant shall have
               thirty (30) days from receipt of such notice to contest the
               amount due, failure to so notify Landlord shall represent
               final determination of Tenant's Share of Expenses. If Tenant's
               payments were greater than the actual amount, then such
               overpayment shall be credited by Landlord to Tenant's Share of
               Expenses due under this Section 4(c)(3). If such overpayment
               is determined after termination of this Lease, then such
               overpayment shall be paid by Landlord to Tenant within thirty
               (30) days after the annual expense statement is completed with
               deduction of any remaining sums owed by Tenant to Landlord.

          4)   RENT WITHOUT OFFSET AND LATE CHARGE. As used herein, "Rent"
               shall mean all monetary sums due from Tenant to Landlord. All
               Base Monthly Rent shall be paid by Tenant to Landlord without
               prior notice or demand in advance on the first day of every
               calendar month, at the address shown in Section 1, or such
               other place as Landlord may designate in writing from time to
               time. Whether or not so designated, all other sums due from
               Tenant under this Lease shall constitute Additional Rent,
               payable without prior notice or demand when specified in this
               Lease, but if not specified, then within thirty (30) days of
               demand, during which time the parties will work to resolve any
               good faith disagreements on the amount due. All Rent shall be
               paid without any deduction or offset whatsoever except as
               otherwise specifically provided herein. All Rent shall be paid
               in lawful currency of the United States of America. Proration
               of Rent due for any partial month shall be calculated by
               dividing the number of days in the month for which Rent is due
               by the actual number of days in that month and multiplying by
               the applicable monthly rate. Tenant acknowledges that late
               payment by Tenant to Landlord of any Rent, Additional Rent or
               other sums due under this Lease will cause Landlord to incur
               costs not contemplated by this Lease, the exact amount of such
               cost being extremely difficult and impracticable to ascertain.
               Such costs include, without limitation, processing and
               accounting charges and late charges that may be imposed on
               Landlord by the terms of any encumbrance or note secured by
               the Premises. Therefore, if any Rent or other sum due from
               Tenant is not received within five (5) business days of the
               date due, Tenant shall pay to Landlord an additional sum equal
               to 5% of such overdue payment. Landlord and Tenant hereby
               agree that such late charge represents a fair and reasonable
               estimate of the costs that Landlord will incur by reason of
               any such late payment and that the late charge is in addition
               to any and all remedies available to the Landlord and that the
               assessment and/or collection of the late charge shall not be
               deemed a waiver of any other default. Additionally, all such
               delinquent Rent or other sums, plus this late charge, which
               are more than thirty (30) days past due, shall bear interest
               at the rate of 15 percent per annum. If the interest rate
               specified in this Lease is higher than the rate permitted by
               law, the interest rate is hereby decreased to the maximum
               legal interest rate permitted by law. Any payments of any kind
               returned for insufficient funds will be subject to an
               additional handling charge of $25.00, and thereafter, Landlord
               may require Tenant to pay all future payments of Rent or other
               sums due by money order or cashier's check.

          5)   REVIEW AND AUDIT RIGHT. Tenant shall have the right (no more
               frequently than once per calendar year) to review Landlord's
               books and records pertaining to Expenses for the prior year.
               Tenant may cause an audit of Landlord's books and records
               which will be conducted


                                       7

<PAGE>

               by an independent certified public accountant designated by
               Tenant. If any such audit discloses Tenant overpaid its share
               of Expenses for any calendar year, Landlord shall pay Tenant
               the amount of the overpayment within thirty (30) days after
               the results of the audit have been disclosed to both parties.
               If any such audit discloses that Tenant underpaid its share of
               Expenses during any calendar year, Tenant shall pay Landlord
               the amount of the underpayment within thirty (30) days after
               the results of the audit have been disclosed to both parties.
               All costs and expenses of the audit shall be paid by Tenant;
               however, if the audit shows Landlord overstated Tenant's share
               of expenses for the subject calendar year by more than five
               percent (5%) of the amount actually payable by Tenant,
               Landlord shall reimburse Tenant for the reasonable costs and
               expenses of the audit within thirty (30) days of receipt of
               Tenant's notice of the amount due. Any review or audit of
               Landlord's books and records pertaining to Expenses shall
               occur at the office of the Building manager or at such other
               location in the Seattle Metropolitan Area as Landlord or its
               Building manager may designate and shall occur during the
               normal business hours of the Building manager, unless
               otherwise agreed by Landlord and Tenant. The results of the
               audit and any information obtained by Tenant from the audit or
               Tenant's review of Landlord's books and records shall be kept
               confidential and not disclosed to any other person or entity,
               including any other tenant of the Building or the Project,
               except as required by court order or applicable law.

5.   PREPAID RENT. Tenant shall, in addition to the payment of the first
     month's Rent as set forth in Section 4(a), pay to Landlord the prepaid
     Rent set forth in Section 1(n), and if Tenant is not in default of any
     provisions of this Lease, such prepaid Rent shall be applied toward
     Base Monthly Rent for the months set forth in Section 1(n). Landlord's
     obligations with respect to the prepaid Rent are those of a debtor and
     not of a trustee, and Landlord can commingle the prepaid Rent with
     Landlord's general funds. Landlord shall not be required to pay Tenant
     interest on the prepaid Rent. Landlord shall be entitled to immediately
     endorse and cash Tenant's prepaid Rent; however, such endorsement and
     cashing shall not constitute Landlord's acceptance of this Lease. In
     the event Landlord does not accept this Lease, Landlord shall return
     said prepaid Rent.

6.   DEPOSIT. Upon execution of this Lease, Tenant shall deposit a security
     deposit as set forth in Section 1(l) with Landlord in the form of an
     irrevocable, unconditional letter of credit from an acceptable
     financial institution. The form of the Letter of Credit and the terms
     under which it shall be extinguished is provided in Exhibit H, Form of
     Letter of Credit. If Tenant is in default, Landlord can use the Letter
     of Credit or any portion of it to cure the default or to compensate
     Landlord for any damages sustained by Landlord resulting from Tenant's
     default. Upon demand, Tenant shall immediately restore the Letter of
     Credit to its full amount. In no event will Tenant have the right to
     apply any part of the security deposit to any Rent or other sums due
     under this Lease. If Tenant is not in default at the expiration or
     termination of this Lease, Landlord shall return the Letter of Credit
     to Tenant. Landlord shall not be required to pay Tenant interest on the
     security deposit.

7.   USE OF PREMISES AND PROJECT FACILITIES. Tenant shall use the Premises
     solely for the purposes set forth in Section 1 and for no other purpose
     without obtaining the prior written consent of Landlord, which consent
     shall not be unreasonably withheld, delayed or conditioned. Tenant
     acknowledges that neither Landlord nor any agent of Landlord has made
     any representation or warranty with respect to the Premises or with
     respect to the suitability of the Premises or the Project for the
     conduct of Tenant's business, nor has Landlord agreed to undertake any
     modification, alteration or improvement to the Premises or the Project,
     except as provided in writing in this Lease. Tenant acknowledges that
     Landlord may from time to time, at its sole discretion, make such
     modifications, alterations, deletions or improvements to the Project as
     Landlord may deem necessary or desirable, without compensation or notice
     to Tenant as long as such modifications, alterations, deletions or
     improvements do not materially alter Tenant's use of its Premises.
     Tenant shall promptly comply with all laws, ordinances, orders and
     regulations affecting the Premises and the Project, including, without
     limitation, any rules and regulations that may be attached to this Lease
     and to any reasonable modifications to these rules and regulations as
     Landlord may adopt from time to time. Tenant acknowledges that, except
     for Landlord's obligations pursuant to Section 13, Tenant is solely
     responsible for ensuring that the Premises comply with any and all
     governmental regulations applicable to Tenant's conduct of business on
     the Premises, and that Tenant is solely responsible for any alterations
     or improvements that may be required by such regulations, now existing
     or hereafter adopted. Tenant shall not do or permit anything to be done
     in or about the Premises or bring or keep anything in the Premises that
     will in any way increase the premiums paid by Landlord on its insurance
     related to the Project or which will in any way increase the premiums
     for fire or casualty insurance carried by other tenants in the Project.
     Tenant will not perform any act or carry on any practices that may
     injure the Premises or the Project; that may be a nuisance or menace to
     other tenants in the Project; or that shall in any way interfere with
     the quiet enjoyment of such other tenants. Tenant shall not use the
     Premises for sleeping, washing clothes, cooking or the preparation,
     manufacture or mixing of anything that might emit any objectionable
     odor, noises, vibrations or lights onto such other tenants. If sound
     insulation is required to muffle noise produced by Tenant on the
     Premises, Tenant at its own cost shall provide all necessary insulation.
     Tenant shall not do anything on the premises which will overload any
     existing parking or service to the Premises. Pets and/or animals of any
     type shall not be kept on the Premises.

                                       8

<PAGE>

8.   HAZARDOUS SUBSTANCES; DISRUPTIVE ACTIVITIES

     a.   HAZARDOUS SUBSTANCES.

          (1)  PRESENCE AND USE OF HAZARDOUS SUBSTANCES. Tenant shall not,
               without Landlord's prior written consent, keep on or around
               the Premises, Common Areas or Building, for use, disposal,
               treatment, generation, storage or sale, any substances
               designated as, or containing components designated as
               hazardous, dangerous, toxic or harmful, and/or is subject to
               regulation, statute or ordinance (collectively referred to as
               "Hazardous Substances"). Notwithstanding the preceding
               sentence, Tenant may keep, use, store and dispose of, in, on
               and from the Premises, materials and supplies otherwise
               constituting Hazardous Substances which are customarily used
               for the purposes set forth in Section 1, provided such
               materials and supplies are used, handled and disposed of in
               accordance with all applicable governmental rules,
               regulations, laws and requirements, and in accordance with
               prudent business practices. With respect to any such Hazardous
               Substance, Tenant shall:

               (i)    Comply promptly, timely, and completely with all
                      governmental requirements for reporting, keeping, and
                      submitting manifests, and obtaining and keeping current
                      identification numbers;

               (ii)   Submit to Landlord true and correct copies of all
                      reports, manifests, and identification numbers at the
                      same time as they are required to be and/or are
                      submitted to the appropriate governmental authorities;

               (iii)  Within five (5) days of Landlord's request, submit
                      written reports to Landlord regarding Tenant's use,
                      storage, treatment, transportation, generation,
                      disposal or sale of Hazardous Substances and provide
                      evidence satisfactory to Landlord of Tenant's
                      compliance with the applicable government regulations;

               (iv)   Allow Landlord or Landlord's agent or representative to
                      come on the Premises at reasonable times, with at least
                      twenty four (24) hours prior notice to Tenant (except
                      in an emergency, when no notice is required), to check
                      Tenant's compliance with all applicable governmental
                      regulations regarding Hazardous Substances;

               (v)    Comply with minimum levels, standards or other
                      performance standards or requirements which may be set
                      forth or established for certain Hazardous Substances
                      (if minimum standards or levels are applicable to
                      Hazardous Substances present on the Premises, such
                      levels or standards shall be established by an on-site
                      inspection by the appropriate governmental authorities
                      and shall be set forth in an addendum to this Lease);
                      and

               (vi)   Comply with all applicable governmental rules,
                      regulations and requirements regarding the proper and
                      lawful use, sale, transportation, generation,
                      treatment, and disposal of Hazardous Substances.

          (2)  If Tenant violates any provisions of this section, then any
               and all costs incurred by Landlord and associated with
               Landlord's monitoring of Tenant's compliance with this Section
               8, including Landlord's attorneys' fees and costs, shall be
               Additional Rent and shall be due and payable to Landlord
               immediately upon demand by Landlord.

     b.   CLEANUP COSTS, DEFAULT AND INDEMNIFICATION.

          (1)  Tenant shall be fully and completely liable to Landlord for
               any and all cleanup costs, and any and all other charges,
               fees, penalties (civil and criminal) imposed by any
               governmental authority with respect to Tenant's use, disposal,
               transportation, generation and/or sale of Hazardous
               Substances, in or about the Premises, Common Areas, or
               Building.

          (2)  Tenant shall indemnify, defend and save Landlord and
               Landlord's lender, if any, harmless from any and all of the
               costs, fees, penalties and charges assessed against or imposed
               upon Landlord (as well as Landlord's and Landlord's lender's
               attorneys' fees and costs) as a result of Tenant's use,
               disposal, transportation, generation and/or sale of Hazardous
               Substances.

          (3)  Upon Tenant's default under this Section 8, in addition to the
               rights and remedies set forth elsewhere in this Lease,
               Landlord shall be entitled to the following rights and
               remedies:

               (i)    At Landlord's option, to terminate this Lease immediately;
                      and/or


                                       9

<PAGE>

               (ii)   To recover any and all damages associated with the
                      default, including, but not limited to cleanup costs
                      and charges, civil and criminal penalties and fees,
                      loss of business and sales by Landlord and other
                      tenants of the Building, any and all damages and claims
                      asserted by third parties and Landlord's attorneys'
                      fees and costs.

     c.   DISPOSAL OF WASTE

          (1)  REFUSE DISPOSAL. Tenant shall not keep any trash, garbage,
               waste or other refuse on the Premises except in sanitary
               containers and shall regularly and frequently remove same from
               the Premises. Tenant shall keep all incinerators, containers
               or other equipment used for storage or disposal of such
               materials in a clean and sanitary condition.

          (2)  SEWAGE DISPOSAL. Tenant shall properly dispose of all sanitary
               sewage and shall not use the sewage disposal system (a) for
               the disposal of anything except sanitary sewage or (b) in
               excess of the lesser amount (i) reasonably contemplated by the
               uses permitted under this Lease or (ii) permitted by any
               governmental entity. Tenant shall keep the sewage disposal
               system free of all obstructions and in good operating
               condition.

          (3)  DISPOSAL OF OTHER WASTE. Tenant shall properly dispose of all
               other waste or other matter delivered to, stored upon, located
               upon or within, used on, or removed from, the Premises in such
               a manner that it does not, and will not, adversely affect the
               (a) health or safety of persons, wherever located, whether on
               the Premises or elsewhere (b) condition, use or enjoyment of
               the Premises or any other real or personal property, wherever
               located, whether on the Premises or anywhere else, or (c)
               Premises or any of the improvements thereto or thereon
               including buildings, foundations, pipes, utility lines,
               landscaping or parking areas.

     d.   DISRUPTIVE ACTIVITIES.  Tenant shall not:

          (1)  Produce, or permit to be produced, any intense glare, light or
               heat except within an enclosed or screened area and then only
               in such manner that the glare, light or heat shall not,
               outside the Premises, be materially different from the light
               or heat from other sources outside the Premises;

          (2)  Create, or permit to be created, any sound pressure level
               which will interfere with the quiet enjoyment of any real
               property outside the Premises, or which will create a nuisance
               or violate any governmental law, rule, regulation or
               requirement;

          (3)  Create, or permit to be created, any ground vibration that is
               materially discernible outside the Premises;

          (4)  Transmit, receive or permit to be transmitted or received, any
               electromagnetic, microwave or other radiation which is harmful
               or hazardous to any person or property in, or about the
               Project; or

          (5)  Create, or permit to be created, any noxious odor that is
               disruptive to the business operations of any other tenant in
               the Project.

9.   SIGNAGE. All signing shall comply with rules and regulations set forth
     by Landlord as may be modified from time to time. Tenant shall place no
     window covering (e.g., shades, blinds, curtains, drapes, screens, or
     tinting materials) other than those installed per Exhibit C, stickers,
     signs, lettering, banners or advertising or display material on or near
     exterior windows or doors if such materials are visible from the
     exterior of the Premises, without Landlord's prior written consent.
     Similarly, Tenant may not install any alarm boxes, foil protection tape
     or other security equipment on the Premises without Landlord's prior
     written consent. Any material violating this provision may be destroyed
     by Landlord without compensation to Tenant. Allowed tenant signage is
     provided for in Section 39, Tenant Signage, and Exhibit D, Signage
     Criteria.

10.  PERSONAL PROPERTY TAXES. Tenant shall pay before delinquency all taxes,
     assessments, license fees and public charges levied, assessed or imposed
     upon its business operations as well as upon all trade fixtures,
     leasehold improvements, merchandise and other personal property in or
     about the Premises.

11.  BUILDING PARKING GARAGE.

     a.   GRANT OF NON-EXCLUSIVE RIGHT. Landlord grants to Tenant and
          Tenant's customers, suppliers, employees and invitees, a
          non-exclusive license to use up to 1.9 parking spaces per 1,000
          rentable square feet of the Premises. The estimated number of
          parking spaces is set forth in Section 1(i). Landlord reserves the
          right at any time to grant similar non-exclusive use to other
          tenants, to promulgate rules and regulations relating to the use of
          such parking areas, including reasonable restrictions on parking by
          tenants and employees, to designate specific spaces for the use of
          any tenant, to make changes in the parking layout from time to
          time, and to establish reasonable time limits on parking.


                                       10
<PAGE>

     b.   LOCATION AND DESIGNATION. There shall exist within the Project a
          garage and surface parking area (collectively the "Garage").
          Landlord shall issue to Tenant parking stickers, tags, or access
          cards (collectively referred to herein as a "Parking Permit") in a
          number equal to the number of allocated parking spaces specified in
          Section 11 (a) above. Each Parking Permit will authorize parking in
          the Garage for one (1) car, twenty-four (24) hours a day, seven
          days a week subject to modification as provided in this Section 11.
          Landlord may designate, subject to change from time to time,
          certain areas within the Garage within which each car may be
          parked, and Tenant shall observe such designations. Tenant shall
          observe all reasonable rules and regulations promulgated by
          Landlord from time to time concerning the use of the Garage and
          shall supply such additional information relating to persons
          authorized to use the Garage as may be reasonably requested by
          Landlord from time to time, including automobile license numbers
          related to each Parking Permit. All such rules and regulations will
          apply fairly and equally to all tenants.

     c.   OPERATIONS. Landlord may maintain, at it's sole discretion, within
          the Garage or surface parking area, an area designated "visitor
          parking" which may be made accessible on an exclusive basis to
          visitors, clients and other invitees of Building tenants, including
          Tenant, on an hourly charge basis. Upon the Commencement of this
          Lease, the Garage shall be open to the general public during the
          hours of 7:00 a.m. through 7:00 p.m., Monday through Friday,
          excluding Building holidays. Landlord shall provide an access
          system to the enclosed portion of the Garage for use by Tenant
          during the periods the Garage is not open to the general public.
          Hours during which the general public will have access to the
          Garage shall be determined at Landlord's sole discretion and may be
          adjusted from time to time.

     d.   CHARGES. The initial monthly charge for the Parking Permits to be
          provided Tenant by Landlord shall be the amount set forth in
          Section 1(i) of the Lease. Such rate shall be in effect upon the
          Commencement Date of the Lease, subject to adjustment during each
          year of the Lease term based upon comparable parking rates for
          similar buildings in the Lower Queen Anne area (reflecting any
          applicable federal, state and local taxes and levies), however, in
          no event shall the rate set forth in Section 1(i) be increased for
          Tenant's allocated Parking Permits during the initial twelve (12)
          months of the Lease term and the rate during the second twelve (12)
          months of the lease term shall not be increased more than 5% above
          the rate set forth in Section 1(i). The above stated maximums on
          the percentage increase in rates shall not apply to any of Tenant's
          parking spaces associated with Tenant's expansion per Sections 34
          or 35 of this Lease. Landlord shall maintain a parking validation
          system for use by tenant customers, clients and invitees. Tenant's
          monthly parking charge for all Parking Permits and the charges for
          all validated parking, if any, shall be billed to Tenant and shall
          be due as Additional Rent within ten (10) days after such billing.
          All hourly parking shall be priced comparably to the hourly parking
          rates charged by similar office buildings located in the area
          (reflecting any applicable federal, state and local taxes and
          levies).

     e.   HOV. Parking stalls required by the City of Seattle for Vanpool,
          carpool and other high occupancy vehicle or transportation
          management programs established under a required transportation
          management plan for the Building will be allocated to each tenant
          based upon the proportionate share of Parking Permits assigned that
          tenant for the Building, and any such HOV Parking Permits shall be
          counted against Tenant's total Permit allocation pursuant to
          Section 11(a).

12.  UTILITIES/SERVICES

     a.   UTILITIES/SERVICES. Landlord shall cause public utilities to
          furnish electricity, gas, water and sewer utilized in operating all
          normal facilities serving the Premises; and to furnish Tenant
          during Tenant's occupancy of the Premises:

          (1)  Hot and cold water at those points of supply provided for
               general use of Tenant in the Building; central heating and air
               conditioning in season and at such temperatures and in such
               amounts as are reasonably considered by Landlord to be
               standard for comparable buildings in the Lower Queen Anne
               area. Tenant shall set operating hours for the Building,
               subject to the reasonable approval of Landlord. For purposes
               of this Lease in determining the estimated amount in Section
               1(k), normal business hours for the Building, Common Areas and
               the Garage of the Project are estimated to be 7:00 AM to 6:00
               PM Monday through Friday and 7:00 AM to 1:00 PM Saturdays,
               excluding holidays. Routine maintenance, painting and electric
               lighting service for all public areas and special service
               areas of the Building shall be provided as reasonably
               requested by Tenant. During other than normal business hours
               for the Building such services shall be provided upon request
               of Tenant, and if reasonably available, Tenant shall bear the
               entire cost thereof as Additional Rent. Tenant shall have
               access to the Premises twenty four (24) hours per day, seven
               (7) days per week, including holidays and weekends, subject to
               Building security systems and procedures.

          (2)  Janitorial service on a five (5) day week basis in accordance
               with the janitorial specifications attached hereto as Exhibit
               E (which standards shall be subject to reasonable modification
               by Landlord from time to time to reflect changes in the

                                       11

<PAGE>

               industry). If Tenant requires janitorial service in excess of
               such established standards, and Landlord provides such
               service, Tenant shall pay any additional cost attributable
               thereto as Additional Rent.

          (3)  Electrical facilities to provide sufficient capacity to serve
               the electrical power needs of Landlord's equipment servicing
               the Building and including up to 3.0 watts per square foot of
               Tenant's Premises for convenience outlet loads and Tenant's
               miscellaneous equipment loads. In the event Tenant requires
               electrical service (e.g. the supply of power in a specific
               voltage or amperage configuration) other than what is provided
               by the Building to serve Tenant's equipment, and should the
               installation of such equipment require additional air
               conditioning capacity above that provided by the Building's
               standard system, then the cost of the installation and
               operation of the additional electrical service and air
               conditioning equipment, if any, shall be paid by Tenant.

          In the event Tenant desires any of the aforementioned services
          in amounts in excess of those required to be provided by
          Landlord pursuant to the terms of Section 12(a) above, Tenant
          shall pay Landlord as Additional Rent hereunder the cost of
          providing such additional quantities.

     b.   INTERRUPTION. Failure by Landlord to any extent to furnish any
          service, or any cessation thereof, shall not render Landlord liable
          in any respect for damages to either person or property, nor be
          construed as an eviction of Tenant, nor work an abatement of rent,
          nor relieve Tenant from fulfillment of any covenant or agreement
          hereof. Notwithstanding the foregoing, however, if an interruption
          of services for causes within Landlord's reasonable control
          materially impairs Tenant's ability to effectively use the Premises
          and if such interruption continues for more than three (3)
          consecutive days or ten (10) days out of twenty (20) day period,
          Tenant shall thereafter be entitled to abate rent as to that
          portion of the Premises which cannot be used, until the service is
          restored. Should any of the equipment or machinery utilized in
          supplying the services described herein break down, or for any
          cause cease to function properly, Landlord shall use reasonable
          diligence to repair same promptly, but Tenant shall have no right
          to terminate this Lease, and shall have no claim for rebate or
          abatement of rent or damages, on account of any interruption in
          service occasioned thereby or resulting therefrom. If any
          interruption of services resulting from causes within the
          reasonable control of Landlord continues for thirty (30)
          consecutive days or more, Tenant may terminate this Lease by
          written notice given to Landlord at any time prior to the date on
          which the services are restored or the interference ceases to the
          extent Tenant can reasonably use and occupy the Premises for its
          intended purposes. With respect to an interruption of services
          which results from causes outside the reasonable control of
          Landlord, if such interruption of services continues for more than
          thirty (30) consecutive days, unless the interruption is caused by
          Tenant, or by repairs or alterations requested by Tenant or
          necessary because of acts or omissions of Tenant (or its agents or
          employees), the Base Rent and Additional Rent shall equitably abate
          in proportion to the extent of the interference with Tenant's use
          of the Premises, commencing on the last day of such thirty (30) day
          period until the services are restored or the interference ceases
          to the extent Tenant can again reasonably use and occupy the
          Premises for its intended purposes, and if such interruption of
          services continues for more than one hundred eighty (180)
          consecutive days, Tenant may terminate this Lease by written notice
          given to Landlord at any time prior to the date on which the
          services are restored or the interference ceases to the extent
          Tenant can again reasonably use and occupy the Premises for its
          intended purposes.

13.  MAINTENANCE. Landlord shall maintain, in good condition, the structural
     parts of the Premises, which shall include only the foundations, bearing
     and exterior walls (excluding glass), subflooring and roof (excluding
     skylights), the unexposed electrical, plumbing and sewerage systems,
     including those portions of the systems lying outside the Premises,
     gutters and downspouts on the Building and the heating, ventilating and
     air conditioning system servicing the Premises; provided, however, the
     cost of all such maintenance shall be considered "Expenses" for purposes
     of Section 4(c). Except as provided above, Tenant shall maintain and
     repair the Premises in good condition, including, without limitation,
     maintaining and repairing all walls, storefronts, floors, ceilings,
     interior and exterior doors, exterior and interior windows and fixtures
     and interior plumbing as well as damage caused by Tenant, its agents,
     employees or invitees. Upon expiration or termination of this Lease,
     Tenant shall surrender the Premises to Landlord in the same condition as
     existed at the commencement of the term, except for reasonable wear and
     tear or damage caused by fire or other casualty for which Landlord has
     received all funds necessary for restoration of the Premises from
     insurance proceeds.

14.  ALTERATIONS. Tenant shall not make any alterations to the Premises other
     than Tenant's initial Tenant Improvements per Exhibit F, or to the
     Project, including any changes to the existing landscaping, without
     Landlord's prior written consent, which shall not be unreasonably
     withheld, delayed or conditioned for alterations not affecting
     structural elements or materially altering Building systems. If Landlord
     gives its consent to such alterations, Landlord may post notices in
     accordance with the laws of the state in which the premises are located.
     Any alterations made shall remain on and be surrendered with the
     Premises upon expiration or termination of this Lease, except that
     Landlord may, on or before expiration of the term, elect to require
     Tenant to remove any alterations which Tenant may have made to the
     Premises. At the time Tenant submits plans for alterations to Landlord
     for Landlord's approval, Tenant may request that Landlord elect whether
     such alterations shall be removed at the termination of this Lease, and
     if so requested, Landlord shall make such election simultaneous with its
     approval of the alterations. If Landlord elects to require


                                       12

<PAGE>

     removal of the alterations, then at its own cost Tenant shall restore
     the Premises to the condition designated by Landlord in its election,
     before the last day of the term or within 30 days after notice of its
     election is given, whichever is later.

     Should Landlord consent in writing to Tenant's alteration of the
     Premises, Tenant shall contract with a contractor reasonably approved by
     Landlord for the construction of such alterations, shall secure all
     appropriate governmental approvals and permits, and shall complete such
     alterations with due diligence in compliance with plans and
     specifications reasonably approved by Landlord. All work performed shall
     be done in workmanlike manner and with material (when not specifically
     described in the plans and specifications) of the quality and appearance
     customary in the trade for first-class construction of the type in which
     the Premises are located. All such construction shall be performed in a
     manner which will not interfere with the quiet enjoyment of other
     tenants of the Project. Tenant shall pay all costs for such construction
     and shall keep the Premises and the Project free and clear of all
     mechanics' liens which may result from construction by Tenant. If
     requested by Landlord, Tenant shall post a bond or other security
     reasonably satisfactory to Landlord to protect against liens. Tenant
     will pay directly or reimburse Landlord for any reasonable cost incurred
     by Landlord in reviewing plans and/or monitoring construction.

15.  RELEASE AND INDEMNITY.

     a.   INDEMNITY. Tenant shall indemnify, defend (using legal counsel
          reasonably acceptable to Landlord) and save Landlord and its
          property manager harmless from all claims, suits, losses, damages,
          fines, penalties, liabilities and expenses (including Landlord's
          personnel and overhead costs and attorneys fees and other costs
          incurred in connection with claims, regardless of whether such
          claims involve litigation, but excluding consequential damages such
          as lost profits) resulting from any actual or alleged injury
          (including death) of any person or from any actual or alleged loss
          of or damage to, any property to the extent caused by (i) Tenant's
          occupation, use or improvement of the Premises, or that of its
          employees, agents or contractors, or (ii) any act or omission of
          Tenant or any subtenant, licensee, assignee or concessionaire of
          Tenant, or of any officer, agent, employee, guest or invitee of
          Tenant, or of any such entity in or about the Premises. Tenant
          agrees that the foregoing indemnity specifically covers actions
          brought by its own employees. This indemnity with respect to acts
          or omissions during the term of this Lease shall survive
          termination or expiration of this Lease. The foregoing indemnity is
          specifically and expressly intended to, constitute a waiver of
          Tenant's immunity under Washington's Industrial Insurance Act, RCW
          Title 51, to the extent necessary to provide Landlord with a full
          and complete indemnity from claims made by Tenant and its
          employees, to the extent provided herein. Tenant shall promptly
          notify Landlord of casualties or accidents occurring in or about
          the Premises. LANDLORD AND TENANT ACKNOWLEDGE THAT THE
          INDEMNIFICATION PROVISIONS OF SECTION 8.b AND THIS SECTION 15 WERE
          SPECIFICALLY NEGOTIATED AND AGREED UPON BY THEM.

     b.   LANDLORD INDEMNITY. Except as otherwise provided in this Section 15
          or Section 16, Landlord shall indemnify, defend (using legal
          counsel reasonably acceptable to Tenant) and save Tenant harmless
          from all claims, suits, losses, fines, penalties, liabilities and
          expenses (including Tenant's personnel and overhead costs and
          attorneys' fees and other costs incurred in connection with claims,
          regardless of whether such claims involve litigation, but excluding
          consequential damages such as lost profits) resulting from any
          actual or alleged injury (including death) of any person or from
          any actual or alleged loss of or damage to, any property to the
          extent caused by the intentional misconduct or negligence of
          Landlord or of any employee or agent of Landlord in the Common
          Areas. Landlord agrees that the foregoing indemnity specifically
          covers actions brought by its own employees. This indemnity with
          respect to actions or omissions during the term of this Lease shall
          survive termination or expiration of this Lease. The foregoing
          indemnity is specifically and expressly intended to constitute a
          waiver of Landlord's immunity under Washington's Industrial
          Insurance Act, RCW Title 51, to the extent necessary to provide
          Tenant with a full and complete indemnity from claims made by
          Landlord and its employees to the extent of their negligence.
          LANDLORD AND TENANT ACKNOWLEDGE THAT THE INDEMNIFICATION PROVISIONS
          OF SECTION 15 WERE SPECIFICALLY NEGOTIATED AND AGREED UPON BY THEM.

     c.   RELEASE. Tenant hereby fully and completely waives and releases all
          claims against Landlord for any losses or other damages sustained
          by Tenant or any person claiming through Tenant resulting from any
          accident or occurrence in or upon the Premises, including but not
          limited to: any defect in or failure of Project equipment; any
          failure to make repairs; any defect, failure, surge in, or
          interruption of Project facilities or services; any defect in or
          failure of Common Areas; broken glass; water leakage; the collapse
          of any Building component; or any act, omission or negligence of
          co-tenants, licensees or any other persons or occupants of the
          Building, provided only that the release contained in this Section
          15.b shall not apply to claims for actual damage to persons or
          property (excluding consequential damages such as lost profits)
          resulting directly from Landlord's breach of its express
          obligations under this Lease which Landlord has not cured within a
          reasonable time after receipt of written notice of such breach from
          Tenant or any of Landlord's negligent or willfull misconduct.

     d.   LIMITATION ON INDEMNITY. In compliance with RCW 4.24.115 as in
          effect on the date of this Lease, all provisions of this Lease
          pursuant to which Landlord or Tenant (the "Indemnitor") agrees to
          indemnify the other (the "Indemnitee") against liability for
          damages arising out of bodily injury to Persons or damage to
          property relative to the construction, alteration, repair, addition
          to, subtraction



                                       13
<PAGE>

           from, improvement to, or maintenance of, any building, road, or
           other structure, project, development, or improvement attached to
           real estate, including the Premises, (i) shall not apply to
           damages caused by or resulting from the sole negligence of the
           Indemnitee, its agents or employees, and (ii) to the extent caused
           by or resulting from the concurrent negligence of (a) the
           Indemnitee or the Indemnitee's agents or employees, and (b) the
           Indemnitor or the Indemnitor's agents or employees, shall apply
           only to the extent of the Indemnitor's negligence; PROVIDED,
           HOWEVER, the limitations on indemnity set forth in this Section
           shall automatically and without further act by either Landlord or
           Tenant be deemed amended so as to remove any of the restrictions
           contained in this Section no longer required by then applicable
           law.

      e.   DEFINITIONS. As used in any Section establishing indemnity or
           release of Landlord, "Landlord" shall include Landlord, its
           partners, officers, agents, employees and contractors, and
           "Tenant" shall include Tenant and any person or entity claiming
           through Tenant.

16.   INSURANCE. Tenant, at its cost, shall maintain commercial general
      liability and property damage insurance and products liability
      insurance with a single combined liability limit of $2,000,000,
      insuring against all liability of Tenant and its representatives,
      employees, invitees, and agents arising out of or in connection with
      Tenant's use or occupancy of the Premises. Landlord may, from time to
      time, require modifications of the insurance coverages hereunder to
      reflect insurance coverages commonly provided in similar projects in
      the area. Commercial general liability insurance, products liability
      insurance and property damage insurance shall insure performance by
      Tenant of the indemnity provisions of Section 15. Landlord and its
      management contractor shall be named as additional insured and the
      policy shall contain cross-liability endorsements. On all its personal
      property, at its cost, Tenant shall maintain a policy of standard fire
      and extended coverage insurance with vandalism and malicious mischief
      endorsements and "all risk" coverage on all Tenant's improvements and
      alterations, including without limitation, all items of Tenant
      responsibility described in Section 13 in or about the Premises, to the
      extent of at least 90% of their full replacement value. The proceeds
      from any such policy shall be used by Tenant for the replacement of
      personal property and the restoration of Tenant's improvements or
      alterations. All insurance required to be provided by Tenant under this
      Lease: (a) shall be issued by Insurance companies authorized to do
      business in the state in which the Premises are located with a
      financial rating of at least an A IX status as rated in the most recent
      edition of Best's Insurance Reports; (b) shall be issued as a primary
      policy; shall be on an occurrence basis; and (d) shall contain an
      endorsement requiring at least 30 days prior written notice of
      cancellation to Landlord and Landlord's lender, before cancellation or
      change in coverage, scope or amount of any policy. Tenant shall deliver
      a certificate or copy of such policy together with evidence of payment
      of all current premiums to Landlord within 30 days of execution of this
      Lease. If Tenant fails at any time to maintain the insurance required
      by this Lease, and fails to cure such default within five (5) business
      days of written notice from Landlord then, in addition to all other
      remedies available under this Lease and applicable law, Landlord may
      purchase such insurance on Tenant's behalf and the cost of such
      insurance shall be Additional Rent due within ten (10) days of written
      invoice from Landlord to Tenant.

      Landlord and Tenant release and relieve the other, and waive their
      entire right of recovery for loss or damage to property located within
      or constituting a part or all of the Building or the Project to the
      extent that the loss or damage is covered by (a) the injured party's
      insurance, or (b) the insurance the injured party is required to carry
      under this Article 16, whichever is greater. This waiver applies
      whether or not the loss is due to the negligent acts or omissions of
      Landlord or Tenant, or their respective officers, directors, employees,
      agents, contractors, or invitees. Each of Landlord and Tenant shall
      have their respective property insurers endorse the applicable
      insurance policies to reflect the foregoing waiver of claims, provided
      however, that the endorsement shall not be required if the applicable
      policy of insurance permits the named insured to waive rights of
      subrogation on a blanket basis, in which case the blanket waiver shall
      be acceptable.

17.   DESTRUCTION. If during the term, more than 25% of the Premises or more
      than 10% of the Building are destroyed from any cause, or rendered
      inaccessible or unusable from any cause, Landlord may, in its sole
      discretion, terminate this Lease by delivery of notice to Tenant within
      30 days of such event without compensation to Tenant. If in Landlord's
      estimation, the Premises cannot be restored within 120 days following
      such destruction, the Landlord shall notify Tenant and Tenant may
      terminate this Lease by delivery of notice to Landlord within 30 days
      of receipt of Landlord's notice. If neither Landlord nor Tenant
      terminates this Lease as provided above, then Landlord shall commence
      to restore the Premises in compliance with then existing laws and shall
      complete such restoration with due diligence. In such event, this Lease
      shall remain in full force and effect, but there shall be an abatement
      of Base Monthly Rent and Tenant's Share of Expenses between the date of
      destruction and the date of completion of restoration, based on the
      extent to which destruction interferes with Tenant's use of the
      Premises.

18.   CONDEMNATION.

      a.   TAKING. If all of the Premises are taken by Eminent Domain, this
           Lease shall terminate as of the date Tenant is required to vacate
           the Premises and all Base and Additional Rent shall be paid to
           that date. The term "Eminent Domain" shall include the taking or
           damaging of property by, through or under any governmental or
           statutory authority, and any purchase or acquisition in lieu
           thereof, whether the damaging or taking is by government or any
           other person. If, in the reasonable judgment of Landlord, a taking
           of any part of the Premises by Eminent Domain renders the
           remainder thereof unusable for the business of Tenant (or the cost
           of restoration of the Premises is not commercially

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<PAGE>

           reasonable), the Lease may, at the option of either party, be
           terminated by written notice given to the other party not more
           than thirty (30) days after Landlord gives Tenant written notice
           of the taking, and such termination shall be effective as of the
           date when Tenant is required to vacate the portion of the Premises
           so taken. If this Lease is so terminated, all Base and Additional
           Rent shall be paid to the date of termination. Whenever any
           portion of the Premises is taken by Eminent Domain and this Lease
           is not terminated, Landlord shall at its expense proceed with all
           reasonable dispatch to restore, to the extent of available
           proceeds issued from the taking governmental authority and to the
           extent it is reasonably prudent to do so, the remainder of the
           Premises to the condition they were in immediately prior to such
           taking, and Tenant shall at its expense proceed with all
           reasonable dispatch to restore its personal property and all
           improvements made by it to the Premises to the same condition they
           were in immediately prior to such taking. The Base and Additional
           Rent payable hereunder shall be reduced from the date Tenant is
           required to partially vacate the Premises in the same proportion
           that the Rentable Area taken bears to the total Rentable Area of
           the Premises prior to taking.

      b.   AWARD. Landlord reserves all right to the entire damage award or
           payment for any taking by Eminent Domain, and Tenant waives all
           claim whatsoever against Landlord for damages for termination of
           its leasehold interest in the Premises or for interference with
           its business. Tenant hereby grants and assigns to Landlord any
           right Tenant may now have or hereafter acquire to such damages and
           agrees to execute and deliver such further instruments of
           assignment as Landlord may from time to time request. Tenant
           shall, however, have the right to claim from the condemning
           authority and keep all compensation that may be recoverable by
           Tenant on account of any loss incurred by Tenant in moving
           Tenant's merchandise, furniture, trade fixtures and equipment,
           provided, however, that Tenant may claim and keep such damages
           only if they are awarded separately in the eminent domain
           proceeding and not out of or as part of Landlord's damages.

19.   ASSIGNMENT OR SUBLEASE. Tenant shall not assign or encumber its
      interest in this Lease or the Premises or sublease all or any part of
      the Premises or allow any other person or entity (except Tenant's
      authorized representatives, employees, invitees, or guests) to occupy
      or use all or any part of the Premises without first obtaining
      Landlord's consent, which shall not be unreasonably withheld, delayed
      or conditioned. In determining whether to consent to a proposed
      assignment or subletting, Landlord may consider any commercially
      reasonable basis for approving or disapproving the proposed subletting
      or assignment, including without limitation any of the following: (i)
      whether the clientele, personnel or foot traffic which will be
      generated by the business of the proposed assignee or sublessee is
      consistent in Landlord's reasonable opinion with the businesses of
      other tenants of the Building or the Project, (ii) whether the proposed
      assignee has a net worth and financial strength and credit record
      reasonably satisfactory to Landlord, and (iii) whether the use of the
      Premises by the proposed assignee or sublessee will violate or create
      any potential violation of any laws or a breach or violation of any
      other lease or agreement by which Landlord is bound. No assignment or
      sublease shall release Tenant from the obligation to perform all
      obligations under this Lease unless otherwise agreed in writing by
      Landlord. Any assignment, encumbrance or sublease without Landlord's
      written consent shall be voidable and at Landlord's election, shall
      constitute a default. If Tenant is a partnership, a withdrawal or
      change, voluntary, involuntary or by operation of law of any partner,
      or the dissolution of the partnership, shall be deemed a voluntary
      assignment. If Tenant consists of more than one person, a purported
      assignment, voluntary or involuntary or by operation of law from one
      person to the other shall be deemed a voluntary assignment. If Tenant
      is a corporation, any dissolution, merger, consolidation or other
      reorganization of Tenant, or sale or other transfer of a controlling
      percentage of the capital stock of Tenant, or the sale of at least 25%
      of the value of the assets of Tenant shall be deemed a voluntary
      assignment. The phrase "controlling percentage" means ownership of and
      right to vote stock possessing at least 25% of the total combined
      voting power of all classes of Tenant's capital stock issued,
      outstanding and entitled to vote for election of directors. The two
      proceeding sentences shall not apply to corporations the stock of which
      is traded through an exchange or over the counter. One half (1/2) of
      any rent received by Tenant from its subtenants or assignees in excess
      of the Rent payable by Tenant to Landlord under this Lease and of any
      sums to be paid by an assignee to Tenant in which is attributable to
      the leasehold interest, prepayment of rent or "buying down" rent (less
      the costs and expenses incurred by Tenant in connection with any such
      sublease or assignment) shall be paid to Landlord. If at the time of
      the proposed assignment or subletting, the Project is more than 15%
      vacant, then Tenant shall not charge less on the proposed assignment or
      subletting than 95% of the rents being charged by Landlord for similar
      spaces in the Project. For purposes of this Section 19, the term
      "similar spaces in the Project" shall mean similar as to (i) location
      of the floors(s) within the Project, (ii) views, (iii) types of tenant
      improvements and (iv) use. If Tenant requests Landlord to consent to a
      proposed assignment or subletting, Tenant shall pay to Landlord,
      whether or not consent is ultimately given, $100 or Landlord's
      reasonable out of pocket attorney's fees incurred in connection with
      such request, whichever is greater.

      Notwithstanding any other provision of this Section 19, Tenant may
      sublet all or part of the Premises to its parent corporation, if any;
      any subsidiary corporation of Tenant or its parent corporation; or any
      corporation or other entity owned or controlled by Tenant, its parent
      corporation of any subsidiary of Tenant (each an "Affiliate").
      Furthermore, Tenant may assign this Lease to any Affiliates, or to any
      entity resulting from a merger or consolidation with Tenant, provided
      the assignee's financial condition (i.e., net worth and liquidity) is
      comparable to that of Tenant immediately preceding the date of the
      assignment.

      No interest of Tenant in this Lease shall be assignable by involuntary
      assignment through operation of law (including without limitation the
      transfer of this Lease by testacy or intestacy). Each of the following
      acts shall be considered an involuntary assignment: (a) if Tenant is or
      becomes bankrupt or insolvent, makes an

                                       15


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      assignment for the benefit of creditors, or institutes proceedings
      under the Bankruptcy Act in which Tenant is the bankrupt party; or if
      Tenant is a partnership or consists of more than one person or entity,
      if any partner of the partnership or other person or entity is or
      becomes bankrupt or insolvent, or makes an assignment for the benefit
      of creditors; or (b) if a writ of attachment or execution is levied on
      this Lease; or (c) if in any proceeding or action to which Tenant is a
      party, a receiver is appointed with authority to take possession of the
      Premises. An involuntary assignment shall constitute a default by
      Tenant and Landlord shall have the right to elect to terminate this
      Lease, in which case this Lease shall not be treated as an asset of
      Tenant.

20.   TENANT DEFAULT.

      a.   EVENTS OF DEFAULT. The occurrence of any of the following shall
           constitute a default by Tenant: (i) a failure to pay Rent,
           Additional Rent or other charge when due, provided that Landlord
           shall not exercise any of its rights under this Section 20(a)(i)
           until Landlord has given Tenant notice of such default and a cure
           period of five (5) business days from receipt of such notice, and
           Tenant has failed to pay such Rent, Additional Rent or other
           charge within such cure period provided that, with respect to sums
           due other than Rent and Additional Rent; (ii) abandonment and
           vacation of the Premises (failure to occupy and operate the
           Premises for ten consecutive days while in monetary default under
           this Lease shall be conclusively deemed an abandonment and
           vacation); (iii) failure to perform any other material provision
           of this Lease, provided that Landlord shall not exercise any of
           its rights under this Section 20(a)(iii) until Landlord has given
           Tenant notice of such default and a cure period of thirty (30)
           days from receipt of such notice, and Tenant has failed to cure
           such default within such cure period, provided further that if
           more than thirty (30) days are required to complete such
           performance, the cure period shall not be deemed to have run so
           long as Tenant commences to cure such default within the thirty
           (30) day period and thereafter diligently pursues its completion;
           or (iv) the making by Tenant of any general assignment or general
           arrangement for the benefit of creditors or the filing by or
           against Tenant of a petition in bankruptcy, including
           reorganization or arrangement, unless in the case of a petition
           filed against Tenant and the same is dismissed within thirty (30)
           days, or the appointment of a trustee or receiver to take
           possession of substantially all of Tenant's assets located at the
           Premises or of Tenant's interest in this Lease. The notices
           required by this Section 20 are intended to satisfy any and all
           notice requirements imposed by law on Landlord and are not in
           addition to any such requirement.

      b.   LANDLORD'S REMEDIES. Landlord shall have the following remedies if
           Tenant is in default. (These remedies are not exclusive; they are
           cumulative and in addition to any remedies now or later allowed by
           law): Landlord may terminate Tenant's right to possession of the
           Premises at any time. No act by Landlord other than giving notice
           to Tenant shall terminate this Lease. Acts of maintenance, efforts
           to relet the Premises, or the appointment of a receiver on
           Landlord's initiative to protect Landlord's interest under this
           Lease shall not constitute a termination of Tenant's right to
           possession. Upon termination of Tenant's right to possession,
           Landlord has the right to recover from Tenant: (1) the worth of
           the unpaid Rent that had been earned at the time of termination of
           Tenant's right to possession; (2) the worth of the amount of the
           unpaid Rent that would have been earned after the date of
           termination of Tenant's right to possession; (3) any other amount,
           including but not limited to, expenses incurred to relet the
           Premises, court, attorney and collection costs, necessary to
           compensate Landlord for all detriment caused by Tenant's default.
           "The Worth," as used for Item (1) in this Paragraph 21 is to be
           computed by allowing interest at the rate of 15 percent per annum.
           If the interest rate specified in this Lease is higher than the
           rate permitted by law, the interest rate is hereby decreased to
           the maximum legal interest rate permitted by law. "The Worth" as
           used for Item (2) in this Paragraph 21 is to be computed by
           discounting the amount at the discount rate of the Federal Reserve
           Bank of San Francisco at the time of termination of Tenant's right
           of possession.

21.   LANDLORD DEFAULT. Landlord shall not be in default unless Landlord
      fails to perform its obligations within thirty (30) days after notice
      by Tenant, specifying wherein Landlord has failed to perform; provided,
      that if the nature of Landlord's obligation is such that more than
      thirty (30) days are required for performance, Landlord shall not be in
      default if Landlord commences performance within thirty (30) days of
      Tenant's notice and thereafter diligently completes performance within
      a reasonable time. Tenant's rights under this Lease shall be limited to
      actions for damages and/or specific performance, and no default by
      Landlord shall entitle Tenant to withhold or offset rent, terminate
      this Lease or to engage in self-help remedies, provided only as
      follows: If Landlord is in default under this Lease, and such default
      materially adversely affects Tenant's ability to do business from the
      Premises, and Landlord fails to cure such default within a commercially
      reasonable time for emergencies and otherwise within thirty (30) days
      after written notice from Tenant (provided that if such default cannot
      be cured with 30 days, then if Landlord fails to commence to cure with
      30 days and diligently pursue such cure to completion), then Tenant
      shall, upon two (2) business days prior written notice to Landlord of
      Tenant's intent to cure the default, be entitled to cure the default
      and the reasonable cost of cure shall be reimbursed by Landlord to
      Tenant with thirty (30) days of invoice therefor. If Landlord fails to
      make such reimbursement, then any issues relating to such default and
      cure shall, at either party's election, be resolved by a
      single-arbitrator before the American Arbitration Association ("AAA")
      under the Arbitration Rules of the AAA modified as follows: (i) the
      total time from date of demand for arbitration to final award shall not
      exceed 25 days; (ii) the arbitrator shall be chosen by the AAA without
      submittal of lists and subject to challenge only for good cause shown;
      (iii) all notices may be by telephone or other electronic communication
      with later confirmation in writing; (iv) the time, date, and place of
      the hearing shall be set by the arbitrator in his or her sole
      discretion, provided that

                                       16


<PAGE>


      there be at least 3 days prior notice of the hearing; (v) there shall
      be no post-hearing briefs; (vi) there shall be no discovery except by
      order of the arbitrator; and (vii) the arbitrator shall issue his or
      her award within 7 days after the close of the hearing. The arbitration
      shall be held in the county in which the Premises is located. The
      decision of the arbitrator shall be final and binding on the parties
      and judgment on the award rendered by the arbitrator may be entered in
      any court of competent jurisdiction. The fees and expenses of the
      arbitrator shall be paid half by Landlord and half by Tenant unless the
      arbitrator decides otherwise in its discretion. The parties shall each
      hold harmless and indemnify the arbitrator from any claims arising in
      connection with the arbitration.

22.   ENTRY ON PREMISES. Landlord and its authorized representatives shall
      have the right to enter the Premises at all reasonable times, with
      reasonable notice given to Tenant except in the case of an emergency,
      for any of the following purposes: (a) to determine whether the
      Premises are in good condition and whether Tenant is complying with its
      obligations under this Lease; (b) to do any necessary maintenance and
      to make any restoration to the Premises or the Project that Landlord
      has the right or obligation to perform; (c) to post "for sale" signs at
      any time during the term, to post "for rent" or "for lease" signs
      during the last 90 days of the term, or during any period while Tenant
      is in default; (d) to show the Premises to prospective brokers, agents,
      buyers, tenants or persons interested in leasing or purchasing the
      Premises, at any time during the term; or (e) to repair, maintain or
      improve the Project and to erect scaffolding and protective barricades
      around and about the Premises but not so as to prevent entry to the
      Premises and to do any other act or thing necessary for the safety or
      preservation of the Premises or the Project. Landlord shall not be
      liable in any manner for any inconvenience, disturbance, loss of
      business, nuisance or other damage arising out of Landlord's entry onto
      the Premises as provided in this Section 22. Tenant shall not be
      entitled to an abatement or reduction of Rent if Landlord exercises any
      rights reserved in this Section 22. Landlord shall conduct his
      activities on the Premises as provided herein in a commercially
      reasonable manner so as to limit inconvenience, annoyance or
      disturbance to Tenant to the maximum extent practicable and to execute
      confidentiality agreements relating to entering areas Tenant keeps
      secure for intellectual property reasons. For each of these purposes,
      Landlord shall at all times have and retain a key with which to unlock
      all the doors in, upon and about the Premises, excluding Tenant's
      vaults and safes. Tenant shall not alter any lock or install a new or
      additional lock or bolt on any door of the Premises without prior
      written consent of Landlord. If Landlord gives its consent, Tenant
      shall furnish Landlord with a key for any such lock.

23.   SUBORDINATION. Without the necessity of any additional document being
      executed by Tenant for the purpose of effecting a subordination, and at
      the election of Landlord or any mortgagee or any beneficiary of a Deed
      of Trust with a lien on the Project or any ground lessor with respect
      to the Project, this Lease shall be subject and subordinate at all
      times to (a) all ground leases or underlying leases which may now exist
      or hereafter be executed affecting the Project, and (b) the lien of any
      mortgage or deed of trust which may now exist or hereafter be executed
      in any amount for which the Project, ground leases or underlying
      leases, or Landlord's interest or estate in any of said items is
      specified as security. This subordination shall be self operative,
      provided that so long as Tenant is not in default hereunder beyond the
      applicable Section 20 cure period, Tenant shall have continued
      enjoyment of the Premises free from any disturbance or interruption by
      reason of any foreclosure of Lender's deed of trust or mortgage. In the
      event that any ground lease or underlying lease terminates for any
      reason or any mortgage or Deed of Trust is foreclosed or a conveyance
      in lieu of foreclosure is made for any reason, Tenant shall,
      notwithstanding any subordination, attorn to and become the Tenant of
      the successor in interest to Landlord, at the option of such successor
      in interest. Tenant covenants and agrees to execute and deliver, upon
      demand by Landlord and in the form requested by Landlord any additional
      documents evidencing the priority or subordination of this Lease with
      respect to any such ground lease or underlying leases or the lien of
      any such mortgage or Deed of Trust, subject to the non-disturbance
      provisions contained herein. If Tenant fails to deliver such
      subordination document as required herein, then Tenant hereby
      irrevocably appoints Landlord as attorney-in-fact of Tenant to execute,
      deliver and record any such document in the name and on behalf of
      Tenant.

      Tenant, within ten days from notice from Landlord, shall execute and
      deliver to Landlord, in recordable form, certificates stating that this
      Lease is not in default, is unmodified and in full force and effect, or
      in full force and effect as modified, and stating the modifications.
      This certificate should also state the amount of current monthly Rent,
      the dates to which Rent has been paid in advance, and the amount of any
      security deposit and prepaid Rent. Failure to deliver this certificate
      to Landlord within ten days shall be conclusive upon Tenant that this
      Lease is in full force and effect and has not been modified except as
      may be represented by Landlord.

24.   NOTICE. Any notice, demand or request required hereunder shall be given
      in writing to the party's facsimile number or address set forth in
      Section 1 hereof by any of the following means: (a) personal service;
      (b) electronic communication, whether by telex, telegram or facsimile;
      (c) overnight courier; or (d) registered or certified, first class
      mail, return receipt requested. Such addresses may be changed by notice
      to the other parties given in the same manner as above provided. Any
      notice, demand or request sent pursuant to either subsection (a) or (b)
      hereof shall be deemed received upon such personal service or upon
      dispatch by electronic means with electronic confirmation of receipt.
      Any notice, demand or request sent pursuant to subsection (c) hereof
      shall be deemed received on the business day immediately following
      deposit with the overnight courier and, if sent pursuant to subsection
      (d), shall be deemed received forty-eight (48) hours following deposit
      in the U.S. mail.

25.   WAIVER. No delay or omission in the exercise of any right or remedy by
      Landlord shall impair such right or remedy or be construed as a waiver.
      No act or conduct of Landlord, including without limitation, acceptance
      of the keys to the Premises, shall constitute an acceptance of the
      surrender of the Premises by Tenant before

                                       17


<PAGE>


      the expiration of the term. Only written notice from Landlord to Tenant
      shall constitute acceptance of the surrender of the Premises and
      accomplish termination of the Lease. Landlord's consent to or approval
      of any act by Tenant requiring Landlord's consent or approval shall not
      be deemed to waive or render unnecessary Landlord's consent to or
      approval of any subsequent act by Tenant. Any waiver by Landlord of any
      default must be in writing and shall not be a waiver of any other
      default concerning the same or any other provision of the Lease. TENANT
      SPECIFICALLY ACKNOWLEDGES AND AGREES THAT, WHERE TENANT HAS RECEIVED A
      NOTICE TO CURE DEFAULT (WHETHER RENT OR NON-RENT), NO ACCEPTANCE BY
      LANDLORD OF RENT SHALL BE DEEMED A WAIVER OF SUCH NOTICE, AND,
      INCLUDING BUT WITHOUT LIMITATION, NO ACCEPTANCE BY LANDLORD OF PARTIAL
      RENT SHALL BE DEEMED TO WAIVE OR CURE ANY RENT DEFAULT. LANDLORD MAY,
      IN ITS DISCRETION, AFTER RECEIPT OF PARTIAL PAYMENT OF RENT, REFUND
      SAME AND CONTINUE ANY PENDING ACTION TO COLLECT THE FULL AMOUNT DUE, OR
      MAY MODIFY ITS DEMAND TO THE UNPAID PORTION. IN EITHER EVENT THE
      DEFAULT SHALL BE DEEMED UNCURED UNTIL THE FULL AMOUNT IS PAID IN GOOD
      FUNDS.

26.   SURRENDER OF PREMISES; HOLDING OVER. Upon expiration of the term,
      Tenant shall surrender to Landlord the Premises and all Tenant
      improvements and alterations in good condition, except for ordinary
      wear and tear and alterations Tenant has the right or is obligated to
      remove under the provisions of Section 14 herein. Tenant shall remove
      all personal property including, without limitation, all data and phone
      wires and other improvements which Landlord has required Tenant to
      remove pursuant to Section 14 or Exhibit F of this Lease. Landlord can
      elect to retain or dispose of in any manner Tenant's personal property
      not removed from the Premises by Tenant prior to the expiration of the
      term. Tenant waives all claims against Landlord for any damage to
      Tenant resulting from Landlord's retention or disposition of Tenant's
      personal property. Tenant shall be liable to Landlord for Landlord's
      cost for storage, removal or disposal of Tenant's personal property.

      If Tenant, with Landlord's consent, remains in possession of the
      Premises after expiration or termination of the term, or after the date
      in any notice given by Landlord to Tenant terminating this Lease, such
      possession by Tenant shall be deemed to be a month-to-month tenancy
      terminable as provided under Washington law, by either party. All
      provisions of this Lease, except those pertaining to term and Rent,
      shall apply to the month-to-month tenancy. During any holdover term,
      Tenant shall pay Base Monthly Rent in an amount equal to 150% of Base
      Monthly Rent for the last full calendar month during the regular term
      plus 100% of Tenant's share of Expenses pursuant to Section 4(c)(3).

27.   LIMITATION OF LANDLORD'S LIABILITY. In consideration of the benefits
      accruing hereunder, Tenant agrees that, in the event of any actual or
      alleged failure, breach or default of this Lease by Landlord,
      Landlord's liability under this Lease shall be limited to, and Tenant
      shall look only to Landlord's interest in the Project and the rents and
      proceeds thereof.

28.   MISCELLANEOUS PROVISIONS.

      a.   TIME OF ESSENCE. Time is of the essence of each provision
           of this Lease.

      b.   AUTHORITY. If Tenant is a corporation, Tenant will deliver to
           Landlord, contemporaneously with this Lease, an authorizing
           resolution by Tenant's Board of Directors, authorizing the
           person(s) executing this Lease to do so, or other evidence of such
           person(s) authority as is reasonably satisfactory to Landlord.

      c.   SUCCESSORS. This Lease shall be binding on and inure to the
           benefit of the parties and their successors, except as provided in
           Section 19 herein.

      d.   LANDLORD'S CONSENT. Except as otherwise specifically provided
           herein, any consent required by Landlord under this Lease must be
           granted in writing and may be withheld by Landlord in its sole and
           absolute discretion unless otherwise provided herein.

      e.   COMMISSIONS. Each party represents that it has not had dealings
           with any real estate broker, finder or other person with respect
           to this Lease in any manner, except for the broker identified in
           Section 1(p), who shall be compensated by the party identified in
           Section 1(p). Landlord and Tenant recognize that it is possible
           that they may hereafter make additional agreements regarding
           further extension or renewal of this Lease or a new lease or
           leases for all or one or more parts of the Premises or other space
           in the Project for a term or terms commencing after the
           Commencement Date of this Lease. Landlord and Tenant recognize
           that it is also possible that they may hereafter modify this Lease
           to add additional space or to substitute space as part of the
           Premises. If any such additional agreements, new leases or
           modifications to this Lease are made (except for the exercise of
           Tenant's Option to Lease the Building Three Option Space), unless
           otherwise agreed in writing by Landlord, Landlord shall not have
           any obligation to pay any compensation to any real estate broker
           or to any other third person engaged by Tenant to render services
           to Tenant in connection with negotiating such matters, regardless
           of whether under the circumstances such person is or is not
           regarded by the law as an agent of Landlord.

      f.   OTHER CHARGES. If either party commences any litigation against
           the other party or files an appeal of a decision arising out of or
           in connection with the Lease, the prevailing party shall be
           entitled to recover from the other party reasonable attorney's
           fees and costs of suit. If Landlord employs a

                                       18


<PAGE>


           collection agency to recover delinquent charges, Tenant agrees to
           pay all collection agency and attorneys' fees charged to Landlord
           in addition to Rent, late charges, interest and other sums payable
           under this Lease. Tenant shall pay a charge of $75 to Landlord for
           preparation of a demand for delinquent Rent.

      g.   FORCE MAJEURE. Neither party shall be deemed in default hereof nor
           liable for damages arising from its failure to perform its duties
           or obligations hereunder if such is due to causes beyond its
           reasonable control, including, but not limited to, acts of God,
           acts of civil or military authorities, fires, floods, windstorms,
           earthquakes, strikes or labor disturbances, civil commotion,
           delays in transportation, governmental delays or war, provided
           nothing in this subparagraph shall limit or otherwise modify or
           waive Tenant's obligation to pay Base Rent and Additional Rent as
           and when due pursuant to the terms of this Lease, or Landlord's
           obligation to timely make any payments which Landlord is required
           to make to Tenant pursuant to this Lease.

      h.   RULES AND REGULATIONS. Tenant shall faithfully observe and comply
           with such commercially reasonable, non-discriminatory "Rules and
           Regulations" as Landlord may from time to time adopt by written
           notice. Landlord shall not be responsible to Tenant for the
           violation or non-performance by any other tenant or occupant of
           the building or Project of said tenant or occupant's lease or of
           any of said Rules and Regulations.

      i.   LANDLORD'S SUCCESSORS. In the event of a sale or conveyance by
           Landlord of the Project, the same shall operate to release
           Landlord from any liability under this Lease from and after the
           date of the sale or conveyance, and in such event Landlord's
           successor in interest shall be solely responsible for all
           obligations of Landlord under this Lease.

      j.   INTERPRETATION. This Lease shall be construed and interpreted in
           accordance with the laws of the state in which the Premises are
           located. This Lease constitutes the entire agreement between the
           parties with respect to the Premises and the Project, except for
           such guarantees or modifications as may be executed in writing by
           the parties from time to time. When required by the context of
           this Lease, the singular shall include the plural, and the
           masculine shall include the feminine and/or neuter. "Party" shall
           mean Landlord or Tenant. If more than one person or entity
           constitutes Landlord or Tenant, the obligations imposed upon that
           party shall be joint and several. The enforceability, invalidity
           or illegality of any provision shall not render the other
           provisions unenforceable, invalid or illegal.

      k.   CLEAN AIR ACT. Tenant acknowledges that Landlord has not made any
           portion of the Premises or the Building accessible for smoking in
           compliance with WAC 296-62-12000. If Tenant wishes to make any
           portion of the Premises accessible for smoking, Tenant shall make
           all improvements necessary to comply with all applicable
           governmental rules and regulations. Tenant acknowledges that the
           indemnity contained in Section 15 of the Lease includes, but is
           not limited to claims based on the presence of tobacco smoke as a
           result of the activities of Tenant, its employees, agents, or
           guests.

29.   OPTION TO EXTEND. So long as Tenant is not in material default under
      the terms of the Lease, Tenant shall have the right to extend the term
      of the Lease for two (2) additional terms of five (5) years each (the
      "Extension Terms"). Tenant agrees to notify Landlord in writing of
      Tenant's intent to renew at twelve (12) months prior to the termination
      of the then current lease term. The rental rate during the Extension
      Terms shall be equal to the then Fair Market Rental Rate (adjusted for
      lease concessions) for comparable space located in Lower Queen Anne,
      Seattle, Washington.

      Within thirty (30) days following Tenant's notice to Landlord of
      Tenant's desire to extend the Lease, Landlord shall notify Tenant of
      the proposed Extended Term Base Rent, which shall be equal to the then
      Fair Market Rental Rate of the Premises. Fair Market Rental Rate shall
      be defined as the annual Base Rent (projected from the date of the
      commencement of the payment of annual rental to which it applies) which
      Tenant would expect to pay and Landlord would expect to receive under
      leases of space of comparable size and quality to the Premises and as
      provided for in and on terms and conditions comparable to, this Lease
      covering premises similar to the Premises. Tenant shall have thirty
      (30) days following receipt of Landlord's notice of the proposed
      Extended Term Base Rent, in which to accept such determination; or to
      agree with Landlord on a stipulated Fair Market Rental Rate.

      If Tenant notifies Landlord, within the aforesaid thirty (30) day
      period, that Tenant disputes the Prevailing Market Rate quoted by
      Landlord, the parties shall, during the following thirty (30) days,
      negotiate in good faith to determine the Annual Base Rent for the
      renewal Term. If within said thirty-day period the parties are unable
      to agree on the Annual Base Rent, then within ten (10) days thereafter,
      each party shall select a qualified appraiser experienced in appraising
      commercial rental properties in the vicinity of the Building, who shall
      submit appraisals for the Premises within thirty (30) days of their
      appointment. If the difference between the appraisals is five percent
      (5%) or less, the Prevailing Market Rate shall be determined to be the
      average of the two appraisals. If the difference is greater than five
      percent (5%), then the two appraisers shall select a third qualified
      appraiser who shall submit an appraisal within the thirty (30) days
      following the submission of the first appraisals. The Prevailing Market
      Rate shall then be the average of the two (2) closest appraisals. The
      fees of each appraiser shall be paid by the party appointing the
      appraiser and the fees of the third appraiser, if any, shall be shared
      equally by the parties.


                                       19

<PAGE>


      The option shall be void if, at the time of exercise of such option,
      Tenant is not in possession of the Premises or is in default under this
      Lease or if Tenant fails to deliver the requisite notice thereof within
      the time period specified above. The option granted herein shall not be
      severed from this Lease, separately sold, assigned, or transferred.

30.   RENT ABATEMENT. Notwithstanding anything to the contrary contained
      herein, Tenant shall not be liable for the payment of Annual Base Rent
      or Tenant's Share of Operating Costs for that 22,699 square feet of
      Rental Area of the Premises identified as Floor Two of Building Two
      (Rental Abatement Space), or other full floor in Building Two that
      Tenant may select instead of Floor Two), for the period commencing with
      the Lease Commencement Date and ending on the earlier of (a) the
      commencement of month thirteen (13) of the initial lease term or (b)
      the date that beneficial occupancy of Floor Two of Building Two)
      commences. Should Tenant occupy less than the full floor prior to the
      commencement of month thirteen (13), then the Annual Base Rent and
      Tenant's Share of Operating Costs shall be charged for that portion of
      the floor being occupied. Tenant covenants and agrees to notify
      Landlord immediately at such time as Tenant commences occupancy of the
      Rental Abatement Space. Upon commencement of the thirteenth (13th)
      month of the lease term the full rent as provided for in Section 1
      shall be due and payable no matter how much of the Rental Abatement
      Space is occupied.

      Tenant shall provide Landlord six (6) months prior written notice on
      the occupancy date desired in order to allow for the completion of
      tenant improvements of the Rental Abatement Space.

31.   TENANT IMPROVEMENT ALLOWANCE. Landlord shall provide Tenant with an
      allowance (the "Tenant Improvement Allowance") of up to Thirty Dollars
      ($30.00) per Rentable Square Foot of the Premises initially leased. The
      Tenant Improvement Allowance may be used only for actual out-of-pocket
      costs of labor and materials (including Washington State Sales Tax),
      and for all professional design services necessary for the design and
      permitting of the Tenant Work, provided by qualified third party
      contractors approved by Landlord for construction of the Tenant Work,
      which approval will not be unreasonably withheld, delayed or
      conditioned. The Tenant Work and method of payment is set forth in
      Exhibit F hereto.

32.   ARCHITECTURAL AND ENGINEERING SERVICES. Landlord shall provide Tenant
      with an allowance for schematic space plans performed by an approved
      space planner up to a maximum amount of $.12 per rentable square foot
      of the Premises. This design allowance shall be paid by Landlord within
      twenty (20) days after invoice by Tenant with reasonable documentation
      showing costs actually incurred.

33.   OPTION SPACE. Tenant shall have the option to lease one full floor, up
      to a maximum of two contiguous full floors, of Building Three
      ("Building Three Option Space") by providing written notice to Landlord
      at least thirteen (13) months in advance of the desired delivery date
      of said Building Three Option Space along with the amount of space to
      be leased. The Building Three Option Space shall be Floor One and Floor
      Two of Building Three. The last date on which written notice can be
      given by Tenant to lease this Building Three Option Space is July 1,
      2001. If Tenant gives written notice on the last available date, the
      Building Three Option Space would not be delivered for occupancy until
      August 1, 2002. Landlord shall determine the configuration (the full
      floor to be taken if less than two full floors are required and the
      location on the floor of any space that is more than one full floor but
      less than two full floors) of the Building Three Option Space with
      input from Tenant, once written notice is given by Tenant.

      Landlord reserves the right to either:

      a.   Proceed with construction of Building Three as early as August 1,
           1999 for delivery on or about October 1, 2000; or

      b.   Delay the commencement of construction of Building Three until
           Landlord is in receipt of Tenant's written notice to lease space
           in Building Three.

      Landlord reserves the right to enter into leases with third party
      tenants on Floor Three and Floor Four of Building Three at any time,
      subject to Tenant's Right of First Refusal per Section 35 below.

      Should Landlord elect to commence construction of Building Three prior
      to Tenant providing written notice of its intent to lease the Building
      Three Option Space, Landlord shall hold the Building Three Option Space
      off the market for Tenant until July 1, 2001, which is the last date on
      which Tenant can exercise its option to lease the Building Three Option
      Space.

      Tenant's option to lease all of the Building Three Option Space is
      subject to Tenant meeting certain criterion as described in Exhibit G,
      Option Space Performance Criterion. As further described in Exhibit G,
      Tenant's option to lease the Building Three Option Space shall be
      reduced to one (1) floor (either the first or second floor of Building
      Three at Landlord's sole discretion) if the criterion is not met.

      The Rental Rate for the Option Space shall be the current rental rate
      that Tenant is then paying Landlord under the initial lease term and
      the Landlord Provided Tenant Improvement Allowance for Building Three
      shall be the same as provided for Building Two) under the initial lease
      term. The lease expiration date for the Option Space shall be
      coterminous with the initial lease term for Building Two.

                                       20

<PAGE>


34.   RIGHT OF FIRST REFUSAL. So long as Tenant is not in material default
      under the terms of the lease, Tenant shall have the Right of First
      Refusal (ROFR) to:

      a.   Lease the third and fourth floors of Building Three should
           Landlord exercise its rights to enter into leases with third party
           tenants prior to the time tenant exercises its option to lease its
           Building Three Option Space; and

      b.   Lease any and all contiguous space when it becomes available (ROFR
           Space) throughout the initial term of this Lease and any
           subsequent Extension Term.

      If Landlord receives a bona fide written offer from a third party to
      lease all or part of such ROFR Space, Landlord shall first notify
      Tenant in writing that such ROFR Space is available to Tenant for
      lease. Such Landlord notice shall include the material terms and
      conditions contained in said third party offer (Term, Rent, Tenant
      Improvement Allowance, etc). Tenant shall have ten (10) business days,
      from receipt of Landlord's notice, to respond in writing with its
      intent to lease or not to lease the ROFR Space under substantially the
      same terms and conditions as contained in Landlord's notice.

      If Tenant notifies Landlord of its intent to lease the ROFR Space, then
      Landlord and Tenant shall enter into a written agreement modifying and
      supplementing this Lease and specifying that such ROFR Space is a part
      of the Premises under this Lease and containing other appropriate terms
      and provisions relating to the addition of the ROFR Space to this Lease.

      In the event Tenant does not exercise in writing its intent to lease
      said ROFR Space within ten (10) business days of Landlord's notice to
      Tenant, then Landlord shall thereafter be free to rent such ROFR Space
      to any third party, under substantially the same terms and conditions
      as contained in Landlord's notice, free of Tenant's right to lease the
      ROFR Space. Tenant shall be free during any ongoing period in which the
      ROFR Space remains unleased to request that Landlord re-open
      discussions with Tenant, which Landlord shall do, subject to any
      ongoing discussions that Landlord may then or thereafter engage in with
      other prospective tenants and Landlord's right to lease the ROFR Space
      under substantially the same terms and conditions as contained in
      Landlord's notice.

35.   RIGHT TO TERMINATE. So long as Tenant is not in material default under
      the terms of this Lease, Tenant shall have a one time Right to
      Terminate the Lease effective at the end of the eighty-fourth (84th)
      month of the initial lease term subject to the conditions contained in
      this Section. In order to exercise this Right to Terminate, Tenant
      shall provide Landlord with written notice (`the Notice") by the end of
      the 72nd month of the Initial Lease Term (at least twelve (12) months'
      notice). If Tenant exercises this Right to Terminate, it shall be
      obligated to pay all amounts due under the Lease until the earlier of
      the end of the eighty-fourth (84th) month of the Initial Lease Term or
      the effective date of any third party lease for the Premises, at which
      point Tenant's obligations under the Lease will cease except to the
      extent that there is any (i) difference between the monthly base rent
      paid by the third party tenant, and the Base Monthly Rent due under the
      Lease; and (ii) any rent or other sums owed by Tenant to Landlord from
      the period prior to the effective date of the Termination. In no event
      shall Tenant have any obligations under the Lease after the end of the
      eighty-fourth month, provided Tenant has complied with the terms of
      this Section and has no outstanding defaults under the terms of this
      Lease. Tenant shall, within thirty (30) days of Landlord's receipt of
      Tenant's notice to exercise this Right to Terminate, pay Landlord's
      unamortized costs (based upon a twelve (12) year amortization period
      and an interest rate of eight percent (8%) per annum) including, but
      not limited to, the Tenant Improvement Allowance, Schematic Space Plan
      Allowance and real estate commissions in connection with the initial
      lease of the Premises to the Tenant. This Right to Terminate only
      applies to the Premises in Building Two.

      Tenant may exercise its Right to Terminate under any of the following
      conditions:

      a.   CONTRACTION OF THE PREMISES. If Tenant wishes to occupy a smaller
           premises, Tenant shall submit a written request to Landlord,
           within thirty (30) days of the Notice, to have the size of the
           Premises reduced to the size specified by Tenant. Landlord will
           notify Tenant of its decision whether to grant Tenant's request
           within sixty (60) days of receipt of such request. If Landlord
           elects to reduce the size of the Premises, Tenant will be required
           to pay Landlord's unamortized costs, as described above, within
           thirty (30) days of Landlord's notice that it will allow the size
           of the Premises to be reduced, provided that the amount of such
           unamortized costs shall be prorated based on the size of the
           reduced Premises. If Landlord declines Tenant's request to reduce
           the Premises, then Tenant may exercise its Right to Terminate as
           described above.

      b.   CESSATION OF BUSINESS. Tenant or any successor entity ceases
           having its main administrative offices in the Seattle-Bellevue
           Metropolitan area.

      Tenant and Landlord agree that this Right to Terminate is not to be
      used to facilitate the move of Tenant from 401 Elliott West to another
      building in the Seattle-Bellevue Metropolitan area prior to the end of
      the initial Lease term except as stated in this Section.

                                       21


<PAGE>



36.   EARLY POSSESSION. Tenant shall have the non-exclusive right to possess
      the initial leased premises thirty (30) days prior to Lease
      Commencement for the purpose of the installation of Tenant's furniture,
      fixtures and equipment. Tenant shall not be charged base monthly rent
      or operating expense charges during said Early Possession period.
      Tenant shall coordinate its move-in activities with the contractor's
      working on the site so as not to impede the final completion of the
      Shell & Core Improvements, including punch list type activities. Tenant
      shall be responsible for the removal and disposal of Tenant's furniture
      and fixture vendor's cartons and trash.

37.   TENANT SIGNAGE. Tenant shall have the right, at Tenant's expense, to
      install dominant building signage on the Building as long as it leases
      in excess of fifty percent (50%) of the rentable area of the Building.
      Tenant's signage shall be subject to all governmental codes and
      Landlord's prior written approval, which approval will not be
      unreasonably withheld, delayed or conditioned for signage consistent
      with the Landlord's architectural principles for the Project. Landlord
      shall have the right to withhold its approval of any sign(s) which in
      its reasonable judgment are not harmonious with the design standard of
      the Building. A signage exhibit, providing more detail to size and
      location, is further detailed in Exhibit D. Tenant shall have the
      following signage opportunities:

      a.   Install one monument sign adjacent to the entry, or in the
           landscaped area adjacent to the Building.

      b.   Install two exclusive, back lighted, pin-mounted signs on the top
           parapet of the Building; one sign per wall, on the South, West or
           East elevations (i.e. 2 of those three walls).

38.   FIBER OPTICS. Tenant shall have the right to install satellite dishes,
      fiber optics and related equipment for Tenants sole use at Tenant's
      sole cost, expense and liability, subject to Landlord's approval of the
      location and method of installation, which shall not be unreasonably
      withheld or delayed for installations that do not interfere with other
      electronic installations on the Building. Tenant's rights pursuant to
      this Section shall include the right to make reasonable replacements,
      upgrades and additions subject to the terms of this Section.

39.   USE OF THE ROOF FOR BUSINESS PURPOSES. Tenant shall have the right to
      enter on the roof of the Building from time to time, in accordance with
      the provisions of this Section and with the prior approval of Landlord,
      for the purpose of installing and maintaining, at Tenant's sole cost
      and expense, equipment in connection with Tenant's use of the Premises
      (the "Tenant's Equipment") at locations, designated by Landlord. Tenant
      shall submit drawings, specifications, and installation data for
      Tenant's Equipment to Landlord for its approval prior to installation.

      Installation of Tenant's Equipment shall be accomplished under the
      direct supervision of Landlord and in accordance with reasonable rules
      and regulations prescribed by Landlord. Tenant's Equipment shall be
      grounded in accordance with Underwriters Laboratories, Inc.
      requirements.

      Tenant shall make no penetration of the Building's roof during
      installation or removal of Tenant's Equipment without the prior written
      consent of Landlord. Tenant shall be responsible for the cost of
      repairing all damages to Landlord's property caused by the
      installation, operation, repair, or removal of Tenant's Equipment,
      except to the extent caused by Landlord, its contractors, or employees.
      Furthermore, in the event Landlord determines that the Building roof
      must be repaired or resealed as a direct or indirect result of the
      installation, maintenance, repair, or removal of Tenant's Equipment,
      except to the extent caused by Landlord, its contractors, or employees,
      all such repairing and/or resealing shall be performed by Landlord's
      designated contractor at Tenant's sole cost and expense.

      Upon termination of this Lease, Tenant, at its sole cost, shall remove
      Tenant's Equipment from the roof of the Building, subject to the
      provisions of this Section. Removal of Tenant's Equipment shall be done
      in a manner satisfactory to Landlord.

      If access to the Building roof is required by Tenant at times other
      than normal business hours, Landlord reserves the right to charge
      Tenant any actual costs incurred by Landlord for overtime wages to
      Landlord's employees or contractors.

      Tenant shall obtain and maintain all necessary FCC licenses, if any,
      and all other governmental approvals, licenses, and permits required to
      operate Tenant's Equipment, which operation shall not interfere with
      the quiet enjoyment of the tenants within the Building.

      Tenant agrees that Landlord hereafter shall have the right to install
      and to grant others the right to install transmitting equipment,
      satellite dishes, antennae, and similar equipment on the roof of the
      Building, so long as neither the installation nor operation of such
      equipment interferes with the operation of Tenant's Equipment.

      Tenant agrees that transmissions from Tenant's Equipment shall not
      cause interference with transmissions of other persons currently
      operating communications equipment in the Business Community. Upon
      written notification from Landlord of such interference, Tenant shall
      immediately stop operation of Tenant's Equipment and not resume
      operation until such interference is cured. Any future agreement
      granting another tenant of the Building or any other person the right
      to make rooftop installations shall contain a covenant by such other
      tenant or person that its installation and operation of rooftop
      equipment will not

                                       22

<PAGE>


      interfere with the operation of Tenant's Equipment, and that if such
      interference occurs, such other tenant or other user shall cease
      installation or operation of its equipment until such interference is
      cured.

40.   FOOD SERVICE SPACE. Landlord has committed to Tenant to lease up to
      2,000 square feet of space in the Southeast corner of the first floor
      of Building Two to a third party food service tenant. Landlord has not
      commenced negotiations with any food service vendors and, therefore,
      the exact amount of space to be leased for this use is not finalized.
      Tenant and Landlord shall work together to finalize this layout and
      Tenant agrees to lease the space up to the finalized demising line of
      the food service space. Tenant may, at any time up to the execution of
      Landlord's lease for food service space, exercise its ROFR to lease
      said space.

41.   TENANT PARKING. Notwithstanding the provisions of Section 11.a., four
      (4) parking spaces located under the footprint of Building Two and
      reasonably close to the Building Two elevator may be reserved by Tenant
      to be designated as F5 Network spaces.

42.   EMERGENCY POWER GENERATOR. The Premises shall include an electrical
      generator pad located by Landlord within the underground parking garage
      (the "Generator Pad"). The Generator Pad shall be constructed by Tenant
      in accordance with plans approved in advance by Landlord, which
      approval will not be unreasonably withheld, delayed or conditioned, and
      which plans shall include fencing and such curbing as is necessary to
      contain any fuel spill. Tenant may install on the Generator Pad a
      backup generator and fuel tank (collectively the "Generator"), the
      make, model and design of which shall be subject to Landlord's prior
      approval, which approval will not be unreasonably withheld, delayed or
      conditioned. The design and operation of the Generator and Generator
      Pad shall be such as to avoid material interference with other tenants
      (whether due to vibration, noise, fumes, or otherwise) resulting from
      operation of the Generator. The Generator shall be used only for
      periodic testing and in the event Tenant's primary electrical service
      is interrupted for any reason. All testing shall take place at times
      reasonably selected to minimize interference with other tenants. The
      Generator shall be used only for backup power, and may not be used as a
      primary power source, nor may it be used by any occupant of any other
      premises. The Generator Pad and the Generator shall be subject to all
      terms and conditions of this Lease, including but not limited to
      Sections 8, 15, and 16, provided only that the square footage of the
      Generator Pad shall not be utilized in calculating the Premises
      Rentable Area for the purpose of calculating Base Rent or allocating
      Expenses between the Premises and any larger parcel. Upon expiration or
      earlier termination of this Lease, Tenant shall remove all improvements
      and equipment from the Generator Pad and shall restore same to a clean,
      paved condition, and shall provide such studies or other information as
      is necessary to demonstrate to Landlord's reasonable satisfaction that
      there has been no environmental contamination on the Generator Pad as a
      result of the storage and operation of the generator and fuel tank
      thereon.

IN WITNESS WHEREOF, Landlord and Tenant have executed this Lease as of the
day and year first above written.


Landlord:         401 ELLIOTT WEST L.L.C.

                  BY:      CHERLIN L.L.C.,
                  ITS:     Manager and Member


                  By:
                      --------------------------------
                           Richard L. Carson
                  Its:  Managing Member

                  BY:      KMC-ONE, L.L.C.
                  ITS:     Member

                  By
                     ---------------------------------
                     Stephen K. Koehler, President, Koehler McFadyen & Company
                  Its: Managing Member


Tenant:           F5 NETWORKS, INC.


                  By: /s/ Jeffrey S. Hussey
                       -------------------------------

                  Its:
                       -------------------------------


                  By:
                       -------------------------------

                  Its:
                       -------------------------------


                                       23

<PAGE>




STATE OF WASHINGTON        )
                           )ss.
COUNTY OF KING             )


         I certify that I know or have satisfactory evidence that RICHARD L.
CARSON and STEPHEN K. KOEHLER are the persons who appeared before me, and
said persons acknowledged that they signed this instrument, on oath stated
that they were authorized to execute the instrument and acknowledged it as
the Managing Member on behalf of CHERLIN LLC and KMC-ONE LLC and Member of
401 ELLIOTT WEST LLC to be the free and voluntary act of such party for the
uses and purposes mentioned in the instrument.

           Dated:
                  --------------------


                                         --------------------------------------
                                         (Signature)

                                         --------------------------------------
                                         (Print Name)
                                         Notary Public, in and for the State
                                         of Washington, residing at
                                                                    -----------
                                         My Commission Expires
                                                               ----------------



STATE OF WASHINGTON        )
                           )ss.
COUNTY OF ---------        )


         I certify that I know or have satisfactory evidence that ___________
and ___________ are the persons who appeared before me, and said persons
acknowledged that they signed this instrument, on oath stated that they were
authorized to execute the instrument and acknowledged it as the ___________
and ___________ of ___________ to be the free and voluntary act of such party
for the uses and purposes mentioned in the instrument.

           Dated:
                  --------------------


                                         --------------------------------------
                                         (Signature)

                                         --------------------------------------
                                         (Print Name)
                                         Notary Public, in and for the State
                                         of Washington, residing at
                                                                    -----------
                                         My Commission Expires
                                                               ----------------


                                       24

<PAGE>

                                    EXHIBIT A
                                  THE PREMISES



                                   [FLOORPLAN]

<PAGE>




                                   [FLOORPLAN]

<PAGE>


                                    EXHIBIT B
                                   (continued)
                        LEGAL DESCRIPTION OF THE PROJECT

PARCEL A:
Lots 1 and 2, Block 156, Supplemental Plat of Seattle Tidelands, in King County,
Washington, as shown on the official maps on file in the Office of the
Commissioner of Public Lands at Olympia, Washington; except that portion thereof
lying within the railroad right of way.

PARCEL B:
Lots 3, 4, 5 and 6, Block 156, and Lots 1 and 2, Block 157, Supplemental Plat of
Seattle Tidelands, in King County, Washington, as shown on the official maps on
file in the Office of the Commissioner of Public Lands at Olympia, Washington;
except that portion thereof lying within the railroad right of way.

TOGETHER WITH all that portion of Portland Street lying between Block 156 and
Block 157, vacated by Ordinance Number 57725 of the City of Seattle; except that
portion of said vacated street as conveyed to Northern Pacific Railroad Company
for a right of way by deed recorded under Recording Number 3777400, lying
Southwesterly of the following described line: Beginning at a point in the
Southeasterly line of Lot 2, Block 158, Map of Seattle Tidelands, filed with the
Board of State Land Commissioners at Olympia on March 15, 1895, a distance of
1.75 feet Northeasterly from the Southmost corner of said Lot 2; thence
Northwesterly to a point in the Southeasterly line of Block 156, Map of Seattle
Tidelands, filed with the Board of State Land Commissioners at Olympia on March
15, 1895, a distance of 2.57 feet Northeasterly from the Southmost corner of
said Block 156.

PARCEL C:
Lots 3, 4, 5, 6 and 7, Block 158, Supplemental Plat of Seattle Tidelands, in
King County, Washington, as shown on the official maps on file in the Office of
the Commissioner of Public Lands at Olympia, Washington; except that portion
thereof lying within railroad right of way.

Together with that portion of West Harrison Street vacated by Ordinance Number
119174, of the City of Seattle and recorded under Recording Number 9811210440.

PARCEL D:

The vacated portion of West Republican Street lying between Lot 7 in Block 155,
SEATTLE TIDE LANDS, and Lot 1, Block 156, SEATTLE TIDE LANDS, and between
Elliott Avenue West and Railroad Avenue West, except the Northern Pacific
Railroad Company's right-of-way.



<PAGE>
                                    EXHIBIT C
                              BUILDING 2 & 3 OFFICE

              TENANT BUILDING SHELL AND CORE OUTLINE SPECIFICATIONS

The Building Outline Specifications which follow are intended to establish
the scope and quality of finishes, materials and systems to be furnished by
Landlord for the construction of the basic Building Shell and Core, as well
as the parking structure and landscaped surface parking areas (together
referred therein as the "Shell and Core"). The Building Outline
Specifications are intended to govern the development of the building
drawings through the completion of the final building working drawings and
specifications ("The Contract Documents"). Capitalized terms used and not
defined shall have the meanings given them in the Lease.

Landlord is committed to developing a long-term investment quality product,
which has lasting quality and landmark stature and will be considered in all
respects a first class office building development. This Outline
Specification may be amended, through mutual consent of the parties, during
the completion of the design development and construction document phases of
the design of the buildings. The cost of all maintenance following initial
installation shall be as provided under the Lease.

FOUNDATION SYSTEM

1.   The augercast pile foundation system shall be designed based upon good
     engineering practice, soils bearing analysis from a geotechnical
     engineer and structural load calculations. Typical floor live loads for
     all office floors shall be 80 pounds per square foot, plus an allowance
     of 20 pounds per square foot for partitions. See Superstructure System
     for exceptions.

2.   The foundation system will be constructed with moisture protection and
     foundation drains designed to provide a dry condition in all occupied
     areas including the storage and equipment spaces.

3.   The garage floor will contain floor drains with sand/oil interceptors
     as required by code.

SITE WORK AND LANDSCAPING

1.   All landscaping and site work shall comply with city ordinances, as
     well as the Site Plan and Landscaping Plan approved by the City of
     Seattle Department of Construction and Land Use.

2.   Pedestrian plazas will provide a campus setting for the buildings. The
     plazas will include features developed by the design team and approved
     by the City.

3.   Parking will be contained in a structured parking facility under the
     entire length of the site and in surface landscaped parking areas.

4.   Site lighting shall be consistent with other parts of the Project.
     Buildings will have site fixtures to provide supplemental pedestrian
     area lighting.

5.   Each building will be provided with a service loading area and a trash
     disposal area. All trash areas shall have capacity for disposal of
     recycling materials.

SUPERSTRUCTURE SYSTEM

1.   The garage framing will be composed of cast-in-place concrete columns
     supporting long span concrete girders at 18 to 20 foot space which in
     turn support one way post-tensioned slabs. The office framing will be
     constructed of reinforced concrete utilizing an approximate 9.5 inch
     post-tensioned flat slab. The office floors shall be designed for 80
     pounds per square foot live load plus 20 pounds per square foot for
     partition load, and 36 pounds per square foot for mechanical and
     equipment loads at interior bays and 16 pounds per square foot at
     perimeter bays.

2.   Floor-to-floor heights to be a minimum of 14' - 6", maximum 15' - 0".

3.   Stairs in stair towers will be equal or superior to concrete filled
     steel pan stairs.

ROOF SYSTEM

1.   Roofs shall be warranted by the specified manufacturer for a minimum of
     ten (10) years and a maximum of fifteen (15) years.

EXTERIOR WALL SYSTEM

1.   The primary Building spandrel and column cap material shall be a
     combination of precast concrete and panelized structural brick veneer.
     Exterior vision glass will be a one inch (1") insulated glass system
     (typical size 5' 0" wide by 6' 0" high). An additional 2' - 0" of vision
     glass height is available on Floors 1 and 4. The vision glass shall be
     low reflective, tinted and will have a low e-coating, or equal, to
     enhance

<PAGE>

     its insulating qualities. Vision glass will be supported in aluminum
     frames with a Kynar- type coated finish. The overall U-value for the
     entire facade shall be designed to satisfy the Washington State Energy
     Code.

2.   Storefronts and Building "monumental" entries will be of a lasting
     quality glazing system with framed glass doors with stainless steel or
     chrome trim, frame and hardware. Push/pull entry hardware will be
     stainless steel or chrome. Hinges and hardware will be compatible with
     the Americans with Disabilities Act criteria.

INTERIOR FINISHES

1.   GARAGE ELEVATOR LOBBIES

     a.   Floor:                    Level loop carpeting.

     b.   Walls:                    Split-faced block or other
                                    serviceable material.

     c.   Elevator Fronts:          Metal, factory finished baked
                                    enamel.

     d.   Ceiling:                  Suspended acoustical ceiling.

     e.   Lighting:                 Building standard 2 x 4 Fluorescent
                                    fixtures.

2.   FIRST FLOOR ENTRY AND ELEVATOR LOBBIES

     a.   Floor:                    Custom inset carpet with honed or
                                    flamed stone, quartzite, or other
                                    12" x 12" hard surface border
                                    material.

     b.   Walls:                    50% wood veneer with reveals and 50%
                                    painted GWB. 4" wood base
                                    throughout.

     c.   Elevator Fronts:          Stainless steel.

     d.   Ceiling:                  Painted GWB.

     e.   Lighting:                 Recessed compact fluorescent down
                                    lights and wall washers.

     f.   Entry Doors:              Framed glass doors set
                                    in storefront glazing with stainless
                                    steel or chrome trim, all as
                                    specified above.

     g.   Stair Doors:              Painted metal doors with painted
                                    hollow metal frames.

3.   TENANT FLOOR ELEVATOR LOBBIES

     a.   Floors:                   Concrete sealed and ready for Tenant
                                    finish.

     b.   Walls:                    GWB with reveals (primed and sanded,
                                    ready for Tenant paint).

     c.   Ceiling:                  GWB Facia and Soffit with acoustical
                                    ceiling insert and recessed compact
                                    fluorescent down lights (primed and
                                    sanded, ready for Tenant paint).

     d.   Elevator Fronts/
          Entries: Metal, factory finished baked enamel.

4.   RESTROOMS

     a.   Floors:                   Ceramic tile field with one color
                                    accent tile.

     b.   Base:                     Ceramic tile cove base field with
                                    one color accent tile.

     c.   Walls:                    Ceramic tile full height on all wet
                                    walls with field and two (2) colors
                                    accent tile. Vinyl wall covering as
                                    specified by Owner elsewhere. Full
                                    height and width mirrors over vanity
                                    tops with light cove.

     d.   Ceiling:                  Suspended acoustical ceiling tile.

     e.   Lighting:                 Valance fluorescent lighting over
                                    stalls and vanity, building standard
                                    lights in center of room.

                                       2

<PAGE>

     f.   Vanity Tops:              Granite, with 4" granite backsplash.

     g.   Toilet Partitions:        Ceiling hung, with baked enamel
                                    finish.

     h.   Plumbing Fixtures:        Wall hung vitreous china water
                                    closets (water saver type) equal to
                                    Kohler, American Standard or Eljer.
                                    Topset mounted vitreous china
                                    lavatories equal to Kohler, American
                                    Standard or Eljer.

     i.   Toilet Accessories:       Fully recessed accessories in satin
                                    finish stainless steel equal to
                                    Bobrick. Lav top mounted soap
                                    dispensers with 4" spout and liquid
                                    soap containers below counter.

5.   GARAGE

     a.   Floor:                    Concrete slab, finished with paint
                                    striping applied where applicable.

     b.   Walls:                    Perimeter walls with gunnite finish.
                                    Core walls with painted concrete
                                    masonry units, cast-in-place
                                    concrete and GWB.

     c.   Ceiling:                  Cast-in-place post tensioned
                                    concrete.

     d.   Lighting:                 24 hour lighting using energy
                                    efficient fixtures with antenna
                                    guards. Lighting levels shall be 1.5
                                    fc or greater.

     e.   Graphics:                 Complete garage graphics including
                                    overhead signage, wall graphics and
                                    directional arrows.

6.   GENERAL

     Gypsum Wall Board ("GWB"): Typical interior partitions 5/8" GWB on metal
     studs. GWB ceilings on metal suspension system. Type X as required.
     Moisture resistant at wet and ceramic tile areas. GWB in Building
     lobbies and miscellaneous service rooms.

ELEVATOR SYSTEM

The Building will be served by two (2) geared passenger elevators and one (1)
oversized, 5,000 pound capacity hydraulic freight elevator. The passenger
elevators shall extend to all floors of the Building including the garage. The
freight elevator shall extend to all office floors and be located adjacent to
the first floor loading dock. At Tenant's option, the freight elevator can be
moved and converted to a traction "swing" elevator with a higher ceiling to
handle the movement of freight. The oversized "swing car" will be finished like
the passenger elevators and may be used solely by passengers during peak demand
periods, and both passengers and freight at other times.

1.   The system will include the complete and workmanlike installation of
     elevators, with duplex selective collective operation.

2.   The system response time, as measured by registration of hall calls,
     will not exceed 30 seconds during any up-peak demand with all cars
     in-group service.

3.   The elevators will be equipped with proximity card readers that
     interface directly with the Building card access system. The Building
     card access system will provide the flexibility to program access or
     denial of access to each card reader based upon one or a combination of
     variables, such as days of the year, month or week, time of day, or an
     individual card. The Building security system will be capable of
     printing out a record of each attempted or actual access at any card
     reader in the Buildings. See "Security System" specifications below.

4.   The elevator cabs will be customized utilizing wood or fabric wall
     panels, stone tile and/or carpet flooring. Architectural metal fronts,
     ceiling, and lighting furnished by Cab supplier.

     One (1) car control station will be provided in each standard cab. One
     (1) car control station will be provided in the "swing car" cab.

     Elevators shall conform to all ADA requirements. Pads will be provided
     for one (1) elevator in the Building (the "swing car").

     Standard cab inside height will be eight feet (8'). "Swing car" inside
     height will be approximately nine feet, six inches (9' - 6").

MECHANICAL SYSTEM

The system will be designed and installed to meet all current codes.

                                       3

<PAGE>

1.   PERFORMANCE CRITERIA:

     a.   Summer outside temperature at 85 degrees, system maintains 74
          egrees inside.

     b.   Winter outside temperature at 17 degrees, system maintains 72
          degrees inside.

     c.   Occupant load based on 150 square feet per person, with people
          loads calculated 450 btuh/person, combined sensible and latent.

     d.   Ventilation air designed at 20 CFM per person.

     e.   Cost effective heat reclaim technologies to be applied as required
          by code.

     f.   Provision for "off-loading" capabilities of equipment such as
          pumps, compressors and fans to permit economics and flexibility in
          after hours operation.

     g.   Rooftop equipment will be installed with refrigerants to meet
          current CFC requirements.

     h.   Toilet exhaust and other "dirty air" exhausted directly out of
          Building at roof. These shafts will be sized to accommodate
          exhausting of electrical and communication rooms.

     i.   Mechanical noise levels shall be kept at or below NC40.

     j.   The basic system shall be designed with capacity to cool
          miscellaneous equipment loads of 3.0 watts per square foot.

2.   HVAC SYSTEM

     a.   GARAGE:

          Ventilation only to provide exhaust per current codes.

     b.   BUILDING:

          Rooftop mounted, packaged DX (Direct Expansion) VAV HVAC
          system. Roof curbs, vibration isolation, and sound attenuators
          shall be provided. The Building's roof top equipment will have
          capacity for handling Tenant miscellaneous equipment as
          specified above. The equipment will employ DX units with
          multiple refrigeration circuits that will allow off-hour use
          in selected areas and still have the advantage of economizer
          cooling. System will provide for a full hundred percent (100%)
          outside air economizer when atmospheric conditions are
          appropriate. Building HVAC will be monitored and controlled by
          a Direct Digital Control (DDC) energy management and
          environmental controls system featuring individual zone
          control and after-hours flexibility. Individual zone terminal
          boxes will be "pressure independent," series fan powered
          perimeter terminal boxes capable of multi-staged heating and
          cooling, with cooling only terminal boxes for interior zones.
          The terminal boxes, control wiring and temperature sensors
          will be furnished and installed as part of Tenant work.

     c.   HVAC SYSTEM OPERATING HOURS:

          The computerized environmental control system for the
          equipment will permit an override of the operating schedule to
          serve an individual zone or a predefined group of zones, by
          pushing a button on the thermostatic sensor. Weekends,
          holidays or scheduled "non-business hours" periods can be
          accommodated with the activation of the Building system to
          provide service to reasonably sized sub areas, for a nominal
          extra cost.

PLUMBING

Plumbing work shall include design installation of a complete plumbing system
for buildings including all equipment and systems. All materials installed shall
be new and of commercial quality with the same brand or manufacturer used for
all similar material or equipment. Color of all fixtures shall be white, unless
otherwise specified. Enamelware shall be acid resisting throughout. The
following is a partial list of required systems and services:

     a.   Toilet room fixtures as required by all codes, including ADA.

     b.   All roof and overflow drains per code. Provide floor drains
          with trap primers in all toilet rooms.

     c.   Back-flow Preventer (BFP) and Pressure Reducing Valve (PRV).

     d.   Drinking fountains shall be furnished as Electric Water Cooler
          (EWC) and per ADA

                                       4

<PAGE>

          requirements.

     e.   All waste and vent piping systems.

     f.   All plumbing/piping systems are to be stubbed outside the
          building and include final connections/coordination to
          city/local utilities.

     g.   Access doors and access panels in finished walls, floors, or
          ceilings are required and shall be unobtrusive.

     h.   Storm water piping from roof drains.

     i.   Condensate drainage system connected to all mechanical
          equipment condensate drain pans, connected in turn to the
          building piping system.

















                                       5

<PAGE>

ELECTRICAL SYSTEM FOR THE BUILDING SHELL

The system will be designed and installed to meet all applicable current codes.

1.   MAIN BUILDING SHELL ELECTRICAL SERVICE DESCRIPTION:

     Incoming power will be provided to the Building by the local utility
     ("Utility") via a transformer installed and maintained by the Utility.
     Power will then travel from the transformer vault to the Building's
     main service switchgear which will have multi-level ground-fault
     protection and be sized to provide levels of service, circuit and
     devices as outlined below at a service voltage of 480 volts.

     The main Building service configuration will be a wye, three-phase,
     four-wire service. In addition to utility metering, digital owner
     meters for maximum demand, voltage and amperes will be provided at main
     service switchgear.

     A riser busway, or other reliable feeder system, will carry full
     service capacity through each floor's electrical room from the main
     switchgear in each Building. Lighting and small mechanical system motor
     loads will be served from high voltage (480v/277v) panels located on
     each floor in Building electrical rooms throughout the Building at
     Landlord's expense. Large mechanical loads will be fed from the main
     service switchgear.

     Low voltage (208v/120v) loads will be served through Building Shell &
     Core distribution dry type transformers and two (2) electrical circuit
     panel boards, with 42 circuits each, located on each floor at
     Landlord's expense.

2.   ELECTRICAL POWER CAPACITY:

     Landlord shall provide main (480V/277V) Building electrical service
     capacity (amperage) to satisfy Tenant's reasonable electrical
     requirements. The main building electrical service capacity is designed
     to provide at least 18 watts per square foot of useable area plus an
     additional three (3) watts per square foot to accommodate Tenant's
     electrical needs.

     All electrical work necessary to install Tenant's (280V/120V)
     electrical outlets, and connect them to the main building electrical
     service and Building Shell & Core circuit panels shall be provided for
     under Tenant Work.

3.   LIGHTING:

     a.   Lighting unit power density in Building common and office
          areas will comply with current energy code using energy
          efficient lighting lamp and ballast technology. Offices are
          currently allowed 1.2 watts per gross square foot of area.

     b.   LIGHTING FIXTURES:

          All interior lighting will be fluorescent fixtures of high
          quality and various architectural types (e.g. recessed, wall
          sconces, troffer style, etc.). Exterior lighting will be HID
          (High Intensity Discharge) type. Electronic or energy
          efficient ballasts will be utilized in all fixtures.

          Tenant shall provide its own lighting fixtures in the office
          areas, through its Tenant Work Allowance.

4.   COMMUNICATIONS AND DATA CONSIDERATIONS

     a.   Stacked dedicated, data/telephone closets and sleeve access
          between floors (planned floor penetrations) and to the roof
          for data and communication lines.

     b.   Provide access only for electrical service to the roof for
          power to Tenant's communication devices.

     c.   Separate "isolated ground" wire for sensitive electrical, data
          and communications devices. Access available at all floors.
          Building grounding system will not exceed five (5) ohms to
          ground.

     d.   Access to perimeter wall areas for electrical, phone and data
          outlets, to be furnished and installed by Tenant, shall be
          coordinated in accordance with the Shell and Core construction
          schedule.

     e.   Generic alarm monitoring of mechanical equipment capability in
          the event of power or equipment failure. Critical equipment
          will be furnished with contacts and a modem to relay trouble
          alarms to a PC purchased by Tenant and located on the
          premises.

                                       6

<PAGE>

5.   EMERGENCY POWER

     Emergency generator system and installation shall be a Tenant furnished
     and installed item. Shell and Core emergency lighting and other fire
     life safety code related systems shall be powered by code approved
     emergency power supply.

SECURITY SYSTEM

1.   All perimeter building and garage access points will be protected and
     monitored 24- hours per day, seven days per week by a UL approved
     monitoring station.

2.   A proximity card key access system capable of printing out each use of
     the system for each exterior entrance to each Building, each garage
     gate and each elevator cab. The basic system shall include one printer
     and shall be expandable at Tenant's cost to provide office space access
     control as a part of Tenant's tenant improvements.

FIRE PROTECTION AND LIFE SAFETY SYSTEMS

1.   Fire sprinkler system will be individually valved and alarmed on each
     floor.

2.   The system shall be equipped with monitoring devices for 24-hours per
     day, seven days per week monitoring by a UL approved central monitoring
     station for smoke, waterflow and valve tampering. The monitoring
     service shall be an operating cost.

3.   Fire rated doors, smoke detectors, heat detectors, alarm systems, fire
     extinguishers, fire hose cabinets, standpipes and other such devices
     will be provided as required by code for Building Shell and Core and
     common areas. A central fire alarm system capable of supporting an ADA
     approved system throughout the Building will be provided. Expansion or
     modification of such systems within Tenant areas will be a part of
     Tenant's Improvement costs.

BUILDING STANDARD OFFICE AREA FINISHES INCLUDED WITH THE BUILDING SHELL

The following improvement work shall be provided by Landlord as part of its
Shell and Core work.

1.   Electrical (480V/277V) service distributed to each floor set within
     the building core with two (2) 42 circuit 120V/208V panels and
     transformer provided. Branch circuit wiring to be accomplished under
     Tenant work. (see Electrical System specification above).

2.   Aluminum window sills, aluminum sill extensions and aluminum window
     head. Perimeter GWB (including perimeter columns) tacked to steel stud
     framing. Interior columns are sheathed with GWB tacked to steel stud
     framing.

3.   Sprinkler heads, installed in shell and core work in accordance with
     governing code for unoccupied space.

4.   Base HVAC system installed and operating, including main duct
     distribution on each floor up to, but not including, the series type
     terminal fan units and thermostats. The terminal boxes, thermostats,
     flex duct and diffusers shall be part of Tenant work.

5.   Common area fire alarms, smoke detectors and exit lights installed per
     code and in compliance with the ADA.

6.   First Floor lobby, building restroom facilities, and exterior spaces
     shall be finished in accordance with governing codes and ordinances as
     a part of the Building Shell and Core.

7.   Shell and Core floor shall be flat and level in accordance with the
     industry standards for the type and location of the installation.

8.   Levelor 1" blinds purchased and installed by Landlord with the cost of
     same ($0.25 per square foot of NRA) charged against the Tenant's
     improvement allowance.

                                       7

<PAGE>
                                    EXHIBIT D

                                SIGNAGE CRITERIA


This Exhibit D is a supplement to Section 36 of the certain lease (the "Lease")
between 401 Elliott West LLC (the "Landlord") and F5 Networks, Inc. (the
"Tenant"). This Exhibit further clarifies the criteria for the signage provided
for in Section 36 of the Lease. As stated in the Lease Tenant shall have two
signage opportunites. The criteria for these signs is more specifically
delineated as follows:

1.   MONUMENT SIGN (SIGN "A")

     Tenant shall be allowed to place one monument sign adjacent to the
     building entry, or in the landscaped area adjacent to the Building.
     Approved locations for Sign A are as shown on the attached site plan.

     Sign A shall be an non-illuminated freestanding sign, up to 48" wide by
     48" high as shown on the attached drawing. The parties to the Lease
     shall mutually agree upon the final configuration and materials of Sign
     A.

2.   BUILDING MOUNTED SIGNS (SIGN "B").

     Tenant shall be allowed the exclusive right to place two building
     mounted signs on the top parapet of the Building. Three possible
     locations are available for these two signs: one on the east elevation,
     one on the south elevation and one on the west elevation. These
     possible locations for the two approved signs (Sign B) are as shown on
     the attached elevation plans.

     These signs shall be pin mounted and may be back lighted. The sign
     letters may be as large as 30" high and they shall be centered in the
     top three foot band of the parapet, The parties to the Lease shall
     mutually agree upon the size of any logo, configuration and materials
     of Sign B.


<PAGE>

                                [BUILDING DESIGN]


<PAGE>

                                    EXHIBIT E

                      SPECIFICATIONS FOR CLEANING SERVICES

The Buildings will be serviced five (5) days per week in the following areas:
Corridors, Elevators, Entry, Hallways, Lobby, Lunch Rooms, Coffee Stations,
Office Cubicles, Office Suites, Parking, Restrooms and Stairways.

SERVICE SPECIFICATIONS

A.   SERVICE AREA

     401 ELLIOTT WEST
     Building Two
     Seattle, WA  98119

B.   GENERAL AREAS

     1.   DAILY SERVICES

          a.   Empty and clean all waste receptacles, replacing trash liners
               as needed to prevent odors, spills or any offensive
               appearance. Wash and sanitize waste receptacles, as necessary.
               Trash to be removed to dumpster or compactor provided on site
               by Client.

          b.   Dust ledges and other horizontal surfaces within reach.

          c.   Dust counters, spot wash where required.

          d.   Dust horizontal surfaces of desks, chairs, tables, file
               cabinets and other office furniture. If glass, use glass
               cleaner.

          e.   Vacuum all carpeted traffic areas in offices, lobbies and
               corridors and entrance mats.

          f.   Spot clean minor carpet stains. Report any large/major carpet
               stains to Building Management via logbook.

          g.   Dust mop all resilient and composition floors with treated
               dust mops. Damp mop to remove spills and water stains as
               required.

          h.   Clean, sanitize and polish all drinking fountains.

          i.   Remove all finger marks and smudges from all vertical surfaces
               (i.e., doors, frames, light switches, relites and partitions).

          j.   Remove all lint and physical dirt from fabric upholstered
               chairs, couches, etc.

          k.   Vacuum or brush all conference room chairs and reposition
               under conference tables, be careful not to damage table/chair
               edges.

          l.   Spot clean all glass partitions, relites, all doors, including
               suite entrance doors and adjacent glass \panels.

          m.   Return all chairs and waste baskets to proper position for
               next day's use. n. Clean all coffee stations:

               1.   Wash and wipe counter tops and cabinetry.

               2.   Sweep and damp mop floors.

               3.   Clean sinks if cleared of tenant items.

               4.   Spot clean walls with water only.

               5.   Remove trash, replacing trash liners nightly. Wipe
                    exterior of garbage cans. Sanitize interior of garbage
                    can as needed to prevent odors and offensive appearance.

               6.   Load all cups/mugs into dishwasher. Put in soap and run
                    dishwasher. When clean, put cups/mugs away in cabinets.

          o.   Clean lunch rooms:

               1.   Vacuum all carpeted areas, sweep all hard surface floors
                    and damp mop. Wash and wipe serving area counter tops and
                    cabinet fronts.

               2.   Collect all trash and remove from the premises, place in
                    dumpster or compactor provided on site by Client.

          p.   Do not move items on desks or credenzas while cleaning. Do not
               unplug computers, typewriters, copy machines or other
               electrical equipment.

          q.   Discard only the contents in waste containers. NO OTHER ITEMS
               ARE TO BE DISCARDED UNLESS MARKED AS TRASH. Remove to trash
               compactor or dumpster on site, provided by Client.

          r.   If recycle program is in effect, remove recycle materials to
               containers provided by Client.

          s.   Do not assist the entry of anyone other than the Contractor's
               employees into occupant space or other Building property. All
               Contractors must have AT&T Wireless photo I.D. badge visible
               at all times.

          t.   Report in the control log and to Building Management any
               broken fixtures or other items needing Management attention.

          u.   Maintain neat and orderly janitor supply closets. All
               chemicals must have MSDS information in janitor closet.

          v.   Replace burned out lights, accessible with a six foot step
               ladder, on a nightly basis. Lamps to be provided by Client.

          w.   Building doors are to be remained locked at all times during
               cleaning so as to preclude unauthorized entry.

          x.   Clean elevator cab surfaces and vacuum door tracks.


                             Exhibit E - Page 1

<PAGE>

     2.   WEEKLY SERVICES

          a.   Dust high surfaces (i.e. tops of picture frames, partition
               tops, moldings, cabinets, wall hangings and other wall
               accessories).

          b.   Wet mop all resilient and composition floor surfaces.

          c.   Clean and polish doors, conference tables, executive office
               desks and credenza tops that are cleared.

          d.   Wipe clean and polish all metal hardware throughout the area.

          e.   Vacuum and edge all carpeted areas not vacuumed
               daily.

          f    Vacuum all upholstered furniture in office area.

          g.   Damp wipe all telephones in common areas with an approved
               germicide cleaner. Do not spray solution directly on phone
               equipment.

     3.   MONTHLY SERVICES

          a.   Dust baseboards.

          b.   Vacuum or dust air diffusers.

          c.   Dust venetian blinds.

          d.   Clean and buff all resilient and composition floors.

          e.   Shampoo and extract elevator and elevator lobby carpets.

          f.   Clean and dust interior of fire extinguisher cabinets.

     4.   QUARTERLY CLEANING SERVICE

          a.   Dust overhead lighting fixtures.

          b.   Dust ventilator ducts and vents, vacuum surrounding ceiling
               areas.

          c.   Wash exposed surfaces of filing cabinets.

          d.   Clean and sweep telephone, electrical and janitorial closets.

          e.   Vacuum all carpets with pile lifter to restore pile to its
               original upright position.

     5.   BI-ANNUAL CLEANING SERVICE

          a.   Strip old finish from all tile, clean grout (acid wash if
               Property Manager deems necessary) and V.C.T. floors and
               refinish, per manufacturer's specifications.

          b.   Wipe down inside of overhead lighting fixtures lens cover.

C.   LOBBY, ENTRY AND HALLWAYS

     1.   DAILY SERVICES

          a.   Empty all waste containers, wash and reline as needed. Remove
               trash to dumpster or compactor provided on site by Client.

          b.   Spot clean exterior surface of waste containers.

          c.   Empty and clean all ashtrays and cigarette urns.

          d.   Screen and/or replace sand in cigarette urns. Sand provided by
               Client.

          e.   Clean, sanitize and polish water fountains.

          f.   Dust all plant pots.

          g.   Dust all horizontal surfaces within reach.

          h.   Vacuum carpeted floor surfaces.

          i.   Spot clean minor carpet stains. Report any large/major carpet
               stains to Building Management via logbook.

          j.   Dust mop hard floor surfaces.

          k.   Wet mop hard floor surfaces as necessary.

          l.   Remove gum, tar and other foreign substances from floor
               surfaces.

          m.   Spot clean all marks on walls.

          n.   Clean door thresholds and vacuum entrance walk-off mats.

          o.   Police all interior public areas and planters for debris.

          p.   Replace burned out lights, accessible with a six-foot step
               ladder, on a nightly basis. Lamps to be provided by Client.

          q.   Spot clean all bright work, including but not limited to door
               hardware, kick plates, and hand rails.

          r.   Dust and spot clean to remove smudges the building directory
               and building signage throughout the buildings.

          s.   Maintain all natural stone floor surfaces to retain original
               appearance at installation.

     2.   WEEKLY SERVICES

          a.   Dust baseboards.

          b.   Hose down exterior entrances and walkways.

     3.   MONTHLY SERVICES

          a.   Wash all waste containers.

          b.   Vacuum air diffusers.

                             Exhibit E - Page 2

<PAGE>

          c.   Edge all carpeted surfaces.

          d.   Dust high partitions, ledges and moldings.

     4.   QUARTERLY SERVICES

          a.   Completely wash partitions/walls

          b.   Spot buff (to remove marks, etc.) and refinish restroom tile
               floors.

          c.   Vacuum all carpets with pile lifter to restore pile to its
               original upright position.

     5.   ANNUAL SERVICES

          a.   Dust high partitions, ledges and molding.

D.   ELEVATORS

     1.   DAILY SERVICES

          a.   Vacuum and edge all carpeted floor surfaces.

          b.   Spot clean carpet stains. Report any large/major carpet stains
               to Building Management via logbook.

          c.   Clean and vacuum elevator tracks on every floor.

          d.   Clean both sides of elevator doors.

          e.   Spot clean vertical surfaces.

          f.   Dust all horizontal surfaces.

          g.   Remove gum, tar and other foreign substances from floor.

          h.   Clean and polish all metal work.

          i.   Spot clean elevator call buttons.

     2.   MONTHLY SERVICES

          a.   Dust ceiling fans and vents.

E.   STAIRWAYS

     1.   DAILY SERVICES

          a.   Gather all waste and place for disposal in dumpster or
               compactor provided on site by Client.

          b.   Spot mop spillage.

          c.   Remove gum, tar and other foreign substances from floor.

     2.   WEEKLY SERVICES

          a.   Dust horizontal surfaces within reach.

          b.   Dust handrails.

          c.   Sweep stairs.

     3.   MONTHLY SERVICES

          a.   Spot clean wall surfaces within reach.

F.   RESTROOMS

     1.   DAILY SERVICES

          a.   Check and refill towel, soap, toilet paper, seat covers and
               sanitary napkin dispensers. Consumable supplies provided by
               Client.

          b.   Sweep or dust mop floor surfaces.

          c.   Wet mop floor surfaces with disinfectant solution.

          d.   Dust horizontal surfaces within reach.

          e.   Empty and clean all waste containers and place for disposal in
               dumpster or compactor provided on site by Client.

          f.   Empty and clean all sanitary napkin containers.

          g.   Clean and polish all soap, towel, toilet paper and seat cover
               dispensers.

          h.   Clean and polish all mirrors, bright metal, other fixtures,
               frames and shelves.

          i.   Clean and polish all wash basins.

          j.   Clean and sanitize partitions, counters, toilets, toilet
               seats, wash basins and urinals.

          k.   Clean and polish chrome fixtures.

          l.   Spot clean walls around sinks, towel dispensers, urinals,
               partitions and door frames.

          m.   Remove gum, tar and other foreign substances from floor
               surfaces.

          n.   Report any fixture not working properly to Building Management
               via logbook.

     2.   MONTHLY SERVICES

          a.   Dust or vacuum air diffusers.

                             Exhibit E - Page 3

<PAGE>

          b.   Wash walls, partitions and doors.

          c.   Dust or vacuum light fixtures.

     3.   QUARTERLY SERVICES

          a.   Machine scrub ceramic tile floors. Replace finish per manufacture
               specifications.

G.   BUILDINGS EXTERIOR

     1.   WEEKLY SERVICES

          a.   Police all exterior perimeter sidewalks, complete to gutter.
               Remove all trash and debris, including cigarette butts.

          b.   Sweep sidewalks, benches and gutters adjacent to buildings to
               remove cigarette butts and litter.

          c.   Spot clean all exterior glass at building entrances.

          d.   Spot clean and dust all architectural elements such as ledges,
               mirrors and handrails adjacent to entrances of buildings.

     2.   QUARTERLY SERVICES

          a.   Steam clean, machine scrub or pressure wash exterior sidewalks
               and plaza areas associated with the Buildings.

H.   SERVICE ENTRANCES, TRASH AREAS AND LOADING DOCK

     1.   DAILY SERVICES

          a.   Place all miscellaneous trash and debris, except construction
               material in the appropriate trash receptacle.

          b.   Clean up any construction debris and place in a designated
               area. Notify Client's agent the morning following the work the
               type of said debris and the time associated with the cleaning.
               Keep record of the time and material used for this work for
               back charges to the offending contractor(s). Submit a separate
               invoice within the week in which the work took place outlining
               the scope of work performed and associated costs. Failure to
               report this work per the above guidelines will eliminate
               payment by Client for said work.

          c.   Sweep entire area with sweeping compound to eliminate
               resettling of dust.

          d.   Wet mop any spills or stains.

     2.   WEEKLY SERVICES

          a.   Hose down entire loading dock and service entrance. Deodorize
               and disinfect area, as required.

I.   CARPET CLEANING

     1.   QUARTERLY SERVICES

          a.   Shampoo entry floor lobby, public hallway and garage level
               elevator lobby carpets on first, second and third floors,
               including garage level.

          b.   Shampoo all elevator cab carpets.

J.   PARKING GARAGE

     1.   DAILY SERVICES

          a.   Vacuum all hard surfaced floors associated with elevator
               lobbies, then wet mop with clear water and mop dry.

          b.   Gather all waste and place for disposal in dumpster or
               compactor provided on site by Client.

          c.   Police stairwells and remove debris, gum, tar and other
               foreign substances from the stairs and stair landings. Spot
               mop spillage.

2.   WEEKLY SERVICES

          a.   Dust horizontal surfaces associated with elevator lobbies and
               stairwells.

          b.   Dust handrails.

          c.   Sweep all stairs and landings.

     3.   QUARTERLY SERVICES

          a.   Spot clean wall surfaces in elevator lobbies and stairwells
               within reach.

                             Exhibit E - Page 4


<PAGE>

                                    EXHIBIT F

                               TENANT WORK LETTER

F5 Networks, Inc. (hereinafter called "Tenant") and 401 Elliott West LLC
(hereinafter called "Landlord") are executing simultaneously with this Tenant
Improvement Work Letter ("the Work Letter") a written Lease ("the Lease") for
space in the building known as 401 Elliott West, Building Two, Seattle,
Washington 98119. As further consideration to entering into the Lease, Landlord
and Tenant mutually agree to the following terms and conditions.

I.   LANDLORD WORK AT LANDLORD EXPENSE

     Landlord shall complete the Building Shell and Core in substantial
     accordance with Exhibit C, Building Shell and Core Outline
     Specifications (the "Landlord Work"). As used in this Lease, the
     "Delivery Date" shall be the date the Premises are sufficiently complete
     to allow Tenant to commence construction of Tenant's improvement work
     (the "Tenant Work") when Landlord has substantially completed (excepting
     punch list items and items that do not materially interfere with the
     construction of the Tenant Work) the following items of its Landlord
     Work, provided that in the event the Delivery Date is delayed due to
     Tenant Delay, then the Delivery Date shall be the date on which the
     Delivery Date would have occurred but for the Tenant Delay:

     A.   Building fully enclosed and water tight, including the roof and
          permanent exterior walls.

     B.   Power and lighting electrical service available as described in
          Exhibit C for distribution by the Tenant.

     C.   There shall be satisfactory evidence that:

          1.   The balance of the Landlord Work can be completed prior to the
               Commencement Date; and

          2.   The Tenant's contractor has an opportunity to proceed
               efficiently with the Tenant Building Improvements, subject to
               a requirement of reasonable coordination and cooperation with
               Landlord's Shell and Core contractor.

     Tenant may begin the Tenant Work ahead of the above items being
     completed at Tenant's election provided that 1) Tenant acknowledges such
     action shall establish the Delivery Date, and 2) the Tenant's decision
     to begin the Tenant Work shall not interfere with the Substantial
     Completion of the Premises.

     Except as set forth above and as defined in Exhibit C, all work,
     improvements, finishes and/or equipment required by Tenant and/or
     specified in the approved Tenant Plans for the Premises shall be
     considered the Tenant Work.

II.  LANDLORD WORK AT TENANT EXPENSE

     Upon request by Tenant, Landlord will have certain Building Shell and
     Core work that exceeds the scope of the Landlord Work, as defined
     above, completed during the normal course of construction of the
     Building Shell and Core. This work shall hereinafter be referred to as
     "Shell and Core Tenant Upgrades." Once the scope of the Shell and Core
     Tenant Upgrades are known, Landlord shall provide Tenant with a budget
     for these Upgrades. All Shell and Core Tenant Upgrades, including the
     cost for same, shall be authorized in writing by Tenant and approved in
     writing by Landlord on the same basis as the approval of Tenant's Plans
     (see III.A.4 below). All Shell and Core Tenant Upgrades shall be
     performed by Landlord's contractor under Landlord's supervision.

III. THE TENANT WORK

     A.   TENANT'S PLANS. Tenant shall employ an architect/space planner
          ("Tenant's Architect") as its architect to provide information to
          Landlord as necessary for the completion of Shell and Core Tenant
          Upgrades and to prepare architectural drawings and specifications
          for all layout and improvements to the Premises not included in the
          Landlord Work. Tenant shall also employ all necessary engineers
          (the "Tenant's Engineers") to prepare technical working drawings
          and specifications for all the Tenant Work, including structural
          alterations, mechanical and electrical work. All such drawings and
          specifications are referred to herein as "Tenant's Plans" and shall
          include the "Preliminary Plans", "M & E Working Drawings" and
          "Issued for Construction Documents" all of which are hereinafter
          defined. Tenant's Plans shall be in form and detail sufficient to
          secure all required governmental approvals and shall be completed
          on Auto-Cad (Version 14 or higher).

                                      -1-
<PAGE>

          Tenant's Architect and Tenant's Engineers shall be mutually
          acceptable to Landlord and Tenant. Sparling Engineers and the
          McKinstry Company are hereby approved as Tenant's Engineers for
          mechanical and electrical engineering work. Other architects and
          engineers required in the course of Tenant's Plans will be as
          mutually approved.

          1.   PRELIMINARY PLANS. The "Preliminary Plans" shall be a
               schematic plan (1/8" scale) for the Premises showing interior
               partitions, a preliminary reflected ceiling plan, and rough
               locations and approximate quantities for, any plumbing
               fixtures and phone, data and electrical outlets. Locations for
               special structural and loading requirements in excess of those
               provided for in Exhibit C will be provided to Landlord prior
               to October 1, 1999. The cost of increasing the floor loads
               beyond those identified in Exhibit C, shall be a Shell and
               Core Tenant Upgrade.

          2.   MECHANICAL AND ELECTRICAL ENGINEERED WORKING DRAWINGS AND
               SPECIFICATIONS ("M & E WORKING DRAWINGS"). The Tenant Plans
               shall be engineered to provide for complete mechanical and
               electrical operating systems. Tenant shall contract with
               Tenant Engineers and cause them to prepare M & E Working
               Drawings showing complete plans for electrical and mechanical
               systems including but not limited to, life safety, automation,
               plumbing, and air cooling, ventilating, heating and
               temperature controls. Tenant shall use Landlord's engineers
               for this work: McKinstry & Co. (mechanical) and Sparling
               Engineers (electrical).

          3.   ISSUED FOR CONSTRUCTION DOCUMENTS. The "Issued for
               Construction Documents" shall consist of all drawings (1/8"
               scale) and specifications necessary to construct all Tenant
               Work in form and detail sufficient to secure all required
               governmental approvals and to demonstrate conformity with the
               Landlord's standards and quality. Tenant's Architect and
               Tenant's Engineers are responsible for having all mechanical,
               electrical, life safety and Tenant Work required structural
               drawings complete.

          4.   APPROVAL BY LANDLORD. Tenant's Plans shall be subject to
               Landlord's approval, which approval shall not be unreasonably
               withheld or delayed. Landlord shall be entitled to withhold
               approval if the proposed plans and specifications (i)
               interfere with the structural integrity of the Buildings, (ii)
               overload the utility systems of the Buildings, (iii) violate
               any applicable laws or regulations, (iv) materially affect the
               architectural integrity of the Buildings, or (v) affect the
               future marketability of the Buildings. If Landlord disapproves
               of any of Tenant's Plans, Landlord shall advise Tenant in
               reasonable detail of required revisions and the reasons
               therefor. After being so advised by Landlord, Tenant shall
               promptly submit a redesign, incorporating the revisions
               required by Landlord, for Landlord's approval. If Tenant has
               reason to dispute any Landlord disapproval, then the parties
               shall meet within 5 days and attempt to resolve the dispute.

               If the Parties are unable to resolve their differences as to
               Tenant's Preliminary Plans within 5 days after meeting, then
               either party may initiate an arbitration procedure by
               notifying the other Party of the need to submit their
               disagreements to binding and final arbitration by a mutually
               acceptable arbitrator with at least ten (10) years commercial
               office design experience. If the parties are unable to agree
               on the arbitrator within a period of ten (10) days of notice,
               then either party may request resolution by a single
               arbitrator before the American Arbitration Association, as set
               forth at the end of Lease Section 21.

          5.   SUBMISSION BY TENANT. Tenant shall submit Tenant's Plans to
               Landlord on or before the following dates:

               October 1, 1999:    Structural floor load requirements.
               January 1, 2000:    All remaining Tenant Plans.

          6.   PERMITS. Tenant shall be responsible for the cost and
               scheduling of the submission of Tenant's Plans, in a timely
               manner, for plan check by the City of Seattle and the
               obtaining of a building permit for the Tenant Work.

     B.   TENANT IMPROVEMENT CONSTRUCTION

          1.   Tenant shall be responsible for the construction of the Tenant
               Work in accordance with approved Tenant Plans.

          2.   Tenant shall, upon completion of Tenant's Plans, directly
               contract for the Tenant Work itself and request proposals from
               Landlord's general contractor, as well as other qualified
               tenant work general contractors working under the same
               building trade work rules as

                                      -2-
<PAGE>

               Landlord's general contractor. The qualified list of such
               contractors shall be mutually approved by Tenant and Landlord.
               When a contract is executed between the selected contractor
               and Tenant, said contractor shall be referred to as "Tenant's
               Contractor." Tenant agrees to cooperate with Landlord and
               Tenant's Contractor in the completion of the Tenant Work by
               responding to Landlord's and Tenant's Contractor's requests
               for information in a timely fashion and Landlord agrees to
               respond similarly to Tenant and Tenant's Contractor.

          3.   Tenant shall submit to Landlord a preliminary cost estimate
               for the Tenant Work and shall provide to Landlord a final
               pricing for the Tenant Work when received from Tenant's
               Contractor but not later than fifteen (15) days prior to the
               commencement of the Tenant Work.

          4.   Tenant's construction contract with Tenant's Contractor shall
               be a guaranteed maximum price contract (the "Tenant
               Improvement Construction Contract") and shall contain a
               construction schedule (the "Tenant Improvement Construction
               Schedule") for construction of the Tenant Work. The guaranteed
               maximum price specified in the Construction Contract shall
               include all costs and fees for construction of the Tenant Work
               with the exception of any required governmental permit fees,
               professional fees and Washington State Sales Tax. To the
               extent Tenant obtains any construction warranties from the
               general contractor and/or any of the subcontractors performing
               any of the Tenant Improvement work, it shall assign such
               warranties to Landlord, to the extent assignable, and, in the
               event such warranties are not assignable, Tenant agrees to
               enforce such warranties on Landlord's behalf.

     C.   SCHEDULE

          1.   Provided that Tenant meets the scheduled deadlines for
               preparation and approval of Tenant's Plans, the Delivery Date,
               subject to any Tenant Delay or Force Majure delay, shall be
               February 29, 2000.

     D.   LANDLORD'S ALLOWANCE FOR TENANT WORK

          1.   Landlord shall provide to Tenant a total "Tenant Improvement
               Allowance" as provided in Section 31 of the Lease. The Tenant
               Improvement Allowance shall be applied first toward the costs
               relating to Shell and Core Tenant Upgrades, including
               applicable Washington State Sales Tax, then toward the
               construction of the Tenant Work shown on the final approved
               Tenant's Plans, including applicable Washington State Sales
               Tax. The maximum allowance for Shell and Core Tenant Upgrades
               and Tenant Work shall not exceed $30.00 (Thirty dollars) per
               Rentable Square Foot.

          2.   The Landlord shall pay the cost of the Tenant Work, up to the
               maximum allowance, directly to the Tenant as more fully
               described in Section IV below.

     E.   TENANT DELAY

          1.   The term "Tenant Delay" shall include, but shall not be
               limited to, any delay in the occurrence of the Delivery Date
               or completion of Landlord's Work resulting from:

               a)   Tenant's failure to perform any of its obligations with
                    respect to the schedule dates contained herein or in the
                    Lease, which actually results in a delay of the Delivery
                    Date; or

               b)   Any Tenant materials, finishes or installations called
                    for on the Tenant Plans which are not readily available
                    and, as a result, adversely affect the schedule;

               c)   Any modification by Tenant to the Tenant's Plans that
                    adversely affects the schedule; or

               d)   Any Act by Tenant or its agents and contractors in
                    installing any tenant fixtures or equipment that
                    unreasonably delays the issuance of the Certificate of
                    Occupancy or temporary Certificate of Occupancy for the
                    Premises; or

               e)   Any delay as a result of Section IV.B. Administration of
                    Work, Changes, Additions or Alternations.

                                      -3-
<PAGE>

           Landlord shall make commercially reasonable efforts to mitigate
     the effect of any event that would otherwise cause Tenant Delay,
     provided that Landlord shall not be required to expend additional funds
     to mitigate Tenant Delay unless Tenant agrees in writing to reimburse
     Landlord for such costs.































                                      -4-
<PAGE>

     F.   LANDLORD DELAY

     The term "Landlord Delay" shall mean those construction events within
     the reasonable control of Landlord (i.e. excluding Tenant Delay, force
     majeure and actions for which Landlord is not responsible under this
     Exhibit F) to the extent such event causes:

               a)   a material and unexpected interference with Tenant's
                    construction of the Tenant Work and resulting delay in
                    substantial completion of the Tenant Work, or

               b)   a delay in substantial completion of the Building Shell
                    and Core beyond the reference dates specified in Section
                    3 and this Exhibit F.

     Tenant shall make commercially reasonable efforts to mitigate the
     effect of any event that would otherwise cause Landlord Delay, provided
     that Tenant shall not be required to expend additional funds to
     mitigate Landlord Delay unless Landlord agrees in writing to reimburse
     Tenant for such costs.

     G.   COOPERATION

          The parties agree to use best efforts to cause each of their
          respective consultants, architects, engineers and contractors to
          cooperate with one another so that the Landlord Work and Tenant
          Work are promptly, diligently and efficiently constructed.

     H.   PUNCH LIST

          Within twenty (20) days after Completion of the Building Shell and
          Core, Tenant shall supply to Landlord a written punch list setting
          forth readily apparent additional corrective non-warranty work to
          the Building Shell and Core which Tenant believes is required to be
          performed pursuant to the requirements of Exhibit C. Once Landlord
          has been provided with a punch list in accordance with the
          foregoing, and agrees with the content of the punch list, Landlord
          shall within thirty (30) days of receipt of the punchlist take such
          measures as are necessary to correct such defective work.

IV.  ADMINISTRATION OF WORK

     A.   LANDLORD REIMBURSEMENT

          1.   Landlord shall at the direction of Tenant either reimburse
               Tenant or directly pay Tenant's Contractor (up to the maximum
               amount of the Tenant Allowance remaining after reductions for
               Shell and Core Tenant Upgrades) for the Tenant Work on a
               monthly basis, within twenty (20) days after the receipt of a
               draw request from Tenant's contractor, accompanied by a signed
               Application and Certificate for Payment (in AIA format) from
               Tenant's Architect confirming that the work covered by such
               draw request has been completed to its satisfaction and
               setting forth, inter alia, the percentage of the Tenant Work
               completed to date. This payment request shall also be
               accompanied by partial conditional lien releases from Tenant's
               Contractor covering the Tenant Work performed and/or materials
               and labor supplied through the date of each application for
               payment and full conditional lien releases from each
               subcontractor and supplier which has at that stage completed
               its work and confirmation from Tenant that its general
               contractor is not in default and that the percentage of work
               completed on the draw request is accurate. The reimbursement
               shall be calculated on a percentage of completion basis less a
               retention as called for under the Tenant Improvement
               Construction Contract, but not less than five percent (5%).
               After completion of one hundred percent (100%) of the Tenant
               Work, Landlord shall either reimburse Tenant or directly pay
               Tenant's Contractor for the then unreimbursed balance of the
               allowance for the Tenant Work minus any mutually agreed
               holdback for uncompleted punch list items, within thirty (30)
               days following receipt of a schedule reflecting such costs,
               together with paid invoices supporting such costs, and
               satisfaction of all of the following conditions:

               a)   Receipt by Landlord of a set of "as built" drawings for
                    the Tenant Work and a copy of all warranties in effect
                    with respect to such Tenant Work;

               b)   Receipt by Landlord of a certificate from the Tenant's
                    architect confirming that all Tenant Work have been
                    performed in accordance with the approved plans and
                    specifications, governing codes and ordinances and all
                    punch list items, except mutually agreed items have been
                    corrected;


                                      -5-
<PAGE>

               c)   Receipt by Landlord of reasonable evidence of payment by
                    Tenant of all other costs, including extras and change
                    orders, to its construction contract;

               d)   The receipt of lien releases from the general contractor
                    and all other persons who performed work on or supplied
                    materials for use in or otherwise have lien rights with
                    respect to the Tenant Work;

               e)   Landlord's on-site review of the Tenant Work and its
                    reasonable approval thereof; and

               f)   Issuance of a Certificate of Occupancy for the Premises
                    by the City or satisfactory evidence that said
                    Certificate of Occupancy will be issued for the Premises
                    within the said 30 day period;

               No payment shall be made while Tenant is in default under the
               Lease. If any payment is not made when due, interest shall
               accrue thereon at the rate provided in Section 20.b. of the
               Lease, but Tenant may not offset unpaid amounts against sums
               otherwise due Landlord under this Lease, absent a final
               judgment thereon.

          2.   If any lien is filed with respect to the Premises during the
               course of construction of the Tenant Work, Tenant shall notify
               Landlord in writing describing the cause of the lien and, if
               lien is for reason other than nonpayment by Landlord, the
               Tenant shall remove or otherwise satisfy the lien.

          3.   If Tenant elects to have Landlord directly pay Tenant's
               Contractor per Section IV.A.1 of this Exhibit F, then Tenant
               shall provide Landlord evidence satisfactory that Tenant has
               funds sufficient to fund all amounts above the Tenant
               Allowance.

     B.   CHANGES, ADDITIONS OR ALTERATIONS

          1.   TENANT REQUESTED CHANGES. If Tenant shall request any change,
               addition or alteration in any of the work shown in the
               Tenant's Plans after Landlord's approval thereof (whether the
               result of governmental requirement or otherwise), Tenant shall
               promptly give Landlord a written description of the changes
               requested and submit to Landlord plans and specifications
               describing such change. Provided the plans and specifications
               are complete, Landlord shall expeditiously (but in no event
               longer than within five (5) days after receipt of the complete
               plans and specifications) review such plans and specifications
               and provide to Tenant written approval of proposed changes.
               Landlord's approval shall be governed by III.A.4. above.
               Notwithstanding the foregoing, the costs of any Change Order
               relating to the Tenant Work shall be applied against the
               Tenant Work Allowance to the extent of any remaining balance
               thereof. Notwithstanding anything herein to the contrary,
               Landlord shall have no obligation to agree to or complete any
               Change Order if and to the extent any delay resulting or
               possibly resulting from the same jeopardizes the Delivery Date
               of the Premises, unless Tenant accepts total responsibility
               for such delay and reasonably compensates Landlord for such
               delay.

          2.   CHANGES DURING CONSTRUCTION (SHELL AND CORE TENANT UPGRADES
               AND TENANT WORK). Revisions to the Shell and Core Plans or
               Tenant Plans, if any, are to be accommodated by Field Change
               Orders. A "Field Change Order" is a document which outlines
               the scope of a requested change in the Work as defined by the
               Shell and Core Plans and Tenant Plans and bears the signature
               of Tenant and Landlord representatives approving such change
               in scope. All such plans, specifications, and Field Change
               Orders shall be approved by Landlord and Tenant prior to being
               executed or acted upon by the Landlord's or Tenant's
               Contractors. Landlord and Tenant shall be given 24 hours to
               respond without causing a Landlord or Tenant Delay unless
               otherwise specified in said Field Change Order. In the event
               the Field Change Order increases the cost of the Shell and
               Core or Tenant Work beyond the maximum Tenant Work Allowance,
               Tenant shall pay for the work per the terms of this Exhibit
               and the Lease. As for Tenant Work, Tenant shall pay its
               Contractor per the terms of the construction contract between
               the Tenant and its Contractor.

                                      -6-

<PAGE>

                                    EXHIBIT G

                       OPTION SPACE PERFORMANCE CRITERION



Per Section 33 of the Lease, Tenant has the Option to Expand its Premises into
the Building Three Option Space as defined in said Section 33.

This Exhibit establishes criterion under which Tenant's Building Three Option
Space shall be reduced from a maximum of two full floors to one full floor.

Tenant's Building Three Option Space shall be reduced to one (1) full floor
(either the first or second floor of Building Three at Landlord's sole
discretion) if either one of the following two conditions exist:

     1)   If at August 1, 2000, Tenant does not have cash coverage or the
          ability to finance current operating expenses plus twelve (12)
          months of payments due under the Lease.

     2)   If by December 31, 2000, the number of full time employees working
          within the Premises is less than 240.














                                       1

<PAGE>

                                    EXHIBIT H

                            FORM OF LETTER OF CREDIT

As provided in Section 6 of the Lease, an irrevocable, unconditional Letter of
Credit (the "Letter of Credit") in the amount of $2,500,000 shall be delivered
to Landlord within ten (10) days following the execution of the Lease. The
Letter of Credit will be in form satisfactory to Landlord (see attached draft),
will be a clean sight draft in the required amount in favor of "401 Elliott West
LLC", irrevocable and expiring no less than sixty (60) days after the Lease
expiration date, will be issued by a bank approved by Landlord and will be
unconditionally available to Landlord by Landlord's drafts, at sight.

The Letter of Credit can be an annually renewable Letter of Credit provided that
if the term of Letter of Credit is not extended for at least one year or a
replacement Letter of Credit from a new financial institution, both acceptable
to Landlord, is not issued at least thirty (30) days prior to any expiry date,
then Landlord shall have authority to draw down this Letter of Credit and use
the proceeds as the security deposit per Section 6 of the Lease in lieu of a
Letter of Credit.

The Letter of Credit shall be reduced per the following schedule and conditions:

1)   Upon commencement of the sixty-first (61st) month of the lease, the
     Letter of Credit shall be reduced to $1,500,000 if all the following
     conditions exist as of the commencement of the sixty-first (61st) month.

     a)   Tenant is not then in default under the terms of the lease and
          Tenant has cured all previous defaults, if any, with the Letter of
          Credit having been restored to its full amount required previous to
          this reduction.

     b)   Tenant is not then in default under any of its Corporate Banking
          Loans or Lines of Credit requirements.

     c)   Tenant's total market cap as determined by the price of its common
          stock traded on the NASDAQ or other similar public market is
          greater than $100,000,000.

     d)   Tenant has experienced four consecutive quarters of positive
          earnings during the preceding twelve (12) months, as reported in
          its annual or quarterly reports to Shareholders.

2)   Upon the early termination of the Lease, only per terms of Section 35 of
     the Lease, Right to Terminate, the Letter of Credit shall be
     extinguished and returned to Tenant, less any Rent, Additional Rent or
     Other Sums due under the Lease.

3)   Upon commencement of the ninety-seventh (97th) month of the Lease, the
     Letter of Credit shall be reduced to $1,000,000 if all the following
     conditions exist as of the commencement of the ninety-seventh (97th)
     month.

     a)   Tenant is not then in default under the terms of the lease and
          Tenant has cured all previous defaults, if any, with the Letter of
          Credit having been restored to its full amount required previous to
          this reduction.

     b)   Tenant is not then in default under any of its Corporate Banking
          Loans or Lines of Credit requirements.

     c)   Tenant's total market cap as determined by the price of its common
          stock traded on the NASDAQ or other similar public market is
          greater than $100,000,000.

     d)   Tenant has experienced four consecutive quarters of positive
          earnings during the preceding twelve (12) months, as reported in
          its annual or quarterly reports to Shareholders.


                                       1

<PAGE>

4)   Upon expiration of the initial lease term or the commencement of the
     first renewal term under this Lease, the Letter of Credit shall be
     extinguished and returned to Tenant, less any Rent, Additional Rent or
     Other Sums due under the Lease.









































                                       2

<PAGE>

                      CONSENT OF INDEPENDENT ACCOUNTANTS

We hereby consent to the use in this Registration Statement on Form S-1 of
our reports dated September 2, 1999 relating to the financial statements and
financial statement schedule of F5 Networks, Inc., which appear in such
Registration Statement. We also consent to the references to us under the
headings "Experts" and "Selected Financial Data" in such Registration
Statement.

/s/ PricewaterhouseCoopers LLP

Seattle, Washington
September 8, 1999



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