<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED BALANCE SHEET, CONSOLIDATED STATEMENT OF OPERATIONS AND THE
CONSOLIDATED STATEMENT OF CASH FLOWS INCLUDED IN THE COMPANY'S FORM 10-Q FOR
THE PERIOD ENDING SEPTEMBER 2, 2000, AND IS QUALIFIED IN ITS ENTIRETY BY
REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000846909
<NAME> CABLETRON SYSTEMS, INC.
<MULTIPLIER> 1,000
<CURRENCY> U.S. DOLLARS
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> MAR-03-2001
<PERIOD-START> MAR-01-2000
<PERIOD-END> SEP-02-2000
<EXCHANGE-RATE> 1.00
<CASH> 364,950
<SECURITIES> 194,046
<RECEIVABLES> 188,367
<ALLOWANCES> 19,859
<INVENTORY> 84,934
<CURRENT-ASSETS> 959,354
<PP&E> 294,722
<DEPRECIATION> 198,609
<TOTAL-ASSETS> 1,919,634
<CURRENT-LIABILITIES> 489,762
<BONDS> 0
0
67,959
<COMMON> 1,854
<OTHER-SE> 1,331,299
<TOTAL-LIABILITY-AND-EQUITY> 1,919,634
<SALES> 536,498
<TOTAL-REVENUES> 536,498
<CGS> 292,750
<TOTAL-COSTS> 365,411
<OTHER-EXPENSES> 0
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 18,236
<INCOME-PRETAX> (222,942)
<INCOME-TAX> (74,210)
<INCOME-CONTINUING> (148,732)
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> (165,586)
<EPS-BASIC> (0.90)
<EPS-DILUTED> (0.90)
</TABLE>