<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE FORM
10-Q OF XIRCOM, INC. FOR THE NINE MONTH PERIOD ENDED JUNE 30, 2000 AND IS
QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 9-MOS
<FISCAL-YEAR-END> SEP-30-2000
<PERIOD-START> OCT-01-1999
<PERIOD-END> JUN-30-2000
<CASH> 129,310
<SECURITIES> 230,432
<RECEIVABLES> 68,567
<ALLOWANCES> 15,337
<INVENTORY> 18,473
<CURRENT-ASSETS> 454,534
<PP&E> 102,685
<DEPRECIATION> 41,479
<TOTAL-ASSETS> 572,380
<CURRENT-LIABILITIES> 67,717
<BONDS> 0
0
0
<COMMON> 31
<OTHER-SE> 490,311
<TOTAL-LIABILITY-AND-EQUITY> 572,380
<SALES> 362,067
<TOTAL-REVENUES> 362,067
<CGS> 201,121
<TOTAL-COSTS> 201,121
<OTHER-EXPENSES> 139,566
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 14
<INCOME-PRETAX> 27,582
<INCOME-TAX> 12,126
<INCOME-CONTINUING> 15,456
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> 15,456
<EPS-BASIC> .54
<EPS-DILUTED> .51
</TABLE>