<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
This schedule contains summary financial information extracted from the
Excel Switching Corporation's Consolidated Condensed Financial Statements
for the periods ending June 30, 1999 and is qualified in its entirety by
reference to such financial statements.
</LEGEND>
<MULTIPLIER> 1,000

<S>                             <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1999             DEC-31-1999
<PERIOD-START>                             APR-01-1999             JAN-01-1999
<PERIOD-END>                               JUN-30-1999             JUN-30-1999
<CASH>                                           32940                       0
<SECURITIES>                                     81716                       0
<RECEIVABLES>                                    47749                       0
<ALLOWANCES>                                    (2728)                       0
<INVENTORY>                                      12822                       0
<CURRENT-ASSETS>                                187839                       0
<PP&E>                                           24747                       0
<DEPRECIATION>                                       0                       0
<TOTAL-ASSETS>                                  230582                       0
<CURRENT-LIABILITIES>                            42866                       0
<BONDS>                                           3958                       0
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                           366                       0
<OTHER-SE>                                      183392                       0
<TOTAL-LIABILITY-AND-EQUITY>                    230752                       0
<SALES>                                          43218                   80558
<TOTAL-REVENUES>                                 43218                   80558
<CGS>                                            13689                   25906
<TOTAL-COSTS>                                    13689                   25906
<OTHER-EXPENSES>                                 22854                   40580
<LOSS-PROVISION>                                     0                       0
<INTEREST-EXPENSE>                              (1306)                  (2514)
<INCOME-PRETAX>                                   7981                   14072
<INCOME-TAX>                                      3661                    6796
<INCOME-CONTINUING>                               4320                    9790
<DISCONTINUED>                                       0                       0
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                      4320                    9790
<EPS-BASIC>                                        .12                     .26
<EPS-DILUTED>                                      .10                     .24


</TABLE>