<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY 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 QUARTER
ENDED JUNE 3, 2000 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000846909
<NAME> CABLETRON SYSTEMS, INC.
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 3-MOS
<FISCAL-YEAR-END> MAR-03-2001
<PERIOD-START> MAR-01-2000
<PERIOD-END> JUN-03-2000
<CASH> 309,799
<SECURITIES> 203,853
<RECEIVABLES> 217,197
<ALLOWANCES> 24,613
<INVENTORY> 89,297
<CURRENT-ASSETS> 918,347
<PP&E> 337,657
<DEPRECIATION> 230,468
<TOTAL-ASSETS> 2,083,844
<CURRENT-LIABILITIES> 518,408
<BONDS> 0
0
0
<COMMON> 1,848
<OTHER-SE> 1,498,902
<TOTAL-LIABILITY-AND-EQUITY> 2,083,844
<SALES> 275,064
<TOTAL-REVENUES> 275,064
<CGS> 153,559
<TOTAL-COSTS> 153,559
<OTHER-EXPENSES> 191,452
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> (9,476)
<INCOME-PRETAX> (58,571)
<INCOME-TAX> (20,711)
<INCOME-CONTINUING> (20,711)
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> (37,860)
<EPS-BASIC> (0.21)
<EPS-DILUTED> (0.21)
</TABLE>