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                               CISCO SYSTEMS, INC.

                        STOCK OPTION ASSUMPTION AGREEMENT
                                  V-BITS, INC.
                             1997 STOCK OPTION PLAN


OPTIONEE:  [First_Name] [Last_Name],

               STOCK OPTION ASSUMPTION AGREEMENT effective as of the 6th day of
December, 1999, by Cisco Systems, Inc., a California corporation ("Cisco").

               WHEREAS, the undersigned individual ("Optionee") holds one or
more outstanding options to purchase shares of the common stock of V-Bits, Inc.,
a California corporation ("V-Bits"), which were granted to Optionee under the
V-Bits 1997 Stock Option Plan (the "Plan") and are each evidenced by a Stock
Option Agreement (the "Option Agreement").

               WHEREAS, V-Bits has been acquired by Cisco through the merger of
V-Bits with and into Cisco (the "Merger") pursuant to the Agreement and Plan of
Reorganization, by and between Cisco and V-Bits (the "Merger Agreement").

               WHEREAS, the provisions of the Merger Agreement require Cisco to
assume all obligations of V-Bits under all outstanding options under the Plan at
the consummation of the Merger and to issue to the holder of each outstanding
option an agreement evidencing the assumption of such option.

               WHEREAS, pursuant to the provisions of the Merger Agreement, the
exchange ratio (the "Exchange Ratio") in effect for the Merger is 0.106033318 of
a share of Cisco common stock ("Cisco Stock") for each outstanding share of
V-Bits common stock ("V-Bits Stock").

               WHEREAS, this Agreement became effective immediately upon the
consummation of the Merger (the "Effective Time") in order to reflect certain
adjustments to Optionee's outstanding options that have become necessary by
reason of the assumption of those options by Cisco in connection with the
Merger.

               NOW, THEREFORE, it is hereby agreed as follows:

               1. The number of shares of V-Bits Stock subject to the options
held by Optionee immediately prior to the Effective Time (the "V-Bits Options")
and the exercise price payable per share are set forth below. Cisco hereby
assumes, as of the Effective Time, all the duties and obligations of V-Bits
under each of the V-Bits Options. In connection with such assumption, the number
of shares of Cisco Stock purchasable under each V-Bits Option hereby assumed and
the exercise price payable thereunder have been adjusted to reflect the Exchange
Ratio. Accordingly, the number of shares of Cisco Stock subject to each V-Bits
Option hereby assumed shall be as specified for that option below, and the
adjusted exercise price payable per

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share of Cisco Stock under the assumed V-Bits Option shall also be as indicated
for that option below.

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------
              V-BITS STOCK OPTIONS                            CISCO ASSUMED OPTIONS
-------------------------------------------------------------------------------------------------
                                                      # of Shares
  # of Shares of V-Bits       Exercise Price            of Cisco           Adjusted Exercise
      Common Stock               per Share            Common Stock          Price per Share
-------------------------------------------------------------------------------------------------
<S>                            <C>                  <C>                    <C>
      V-Bits_Shares            $V-Bits_Price         [Cisco_Shares]        [$Cisco_Price]
-------------------------------------------------------------------------------------------------
</TABLE>

               2. The intent of the foregoing adjustments to each assumed V-Bits
Option is to assure that the spread between the aggregate fair market value of
the shares of Cisco Stock purchasable under each such option and the aggregate
exercise price as adjusted pursuant to this Agreement will, immediately after
the consummation of the Merger, be not less than the spread that existed,
immediately prior to the Merger, between the then aggregate fair market value of
the V-Bits Stock subject to the V-Bits Option and the aggregate exercise price
in effect at such time under the Option Agreement. Such adjustments are also
intended to preserve, immediately after the Merger, on a per share basis, the
same ratio of exercise price per option share to fair market value per share
that existed under the V-Bits Option immediately prior to the Merger.

               3. The following provisions shall govern each V-Bits Option
hereby assumed by Cisco:

                             (a) Unless the context otherwise requires, all
               references in each Option Agreement and, if applicable, in the
               Plan (as incorporated into such Option Agreement) (i) to the
               "Company" shall mean Cisco, (ii) to "Common Stock" or "Stock"
               shall mean share of Cisco Stock, (iii) to the "Board" shall mean
               the Board of Directors of Cisco and (iv) to the "Committee" shall
               mean the Compensation Committee of the Cisco Board of Directors.

                             (b) The grant date and the expiration date of each
               assumed V-Bits Option and all other provisions that govern either
               the exercise or the termination of the assumed V-Bits Option
               shall remain the same as set forth in the Option Agreement
               applicable to that option, and the provisions of the Option
               Agreement shall accordingly govern and control Optionee's rights
               under this Agreement to purchase Cisco Stock.

                             (c) Each V-Bits Option shall be assumed by Cisco as
               of the Effective Time. Pursuant to the terms of your Option
               Agreement, seventy-five percent (75%) of the unvested shares
               subject to your option assumed by Cisco in connection with the
               transaction will vest and become exercisable on an accelerated
               basis upon the consummation of the Merger. Each such assumed
               V-Bits Option shall thereafter continue to vest for any remaining
               unvested shares of Cisco Stock subject to that option in
               accordance with the same installment vesting schedule in effect
               under the applicable Option Agreement immediately prior to the
               Effective Time; provided, however, that the number of shares
               subject to each such installment shall be adjusted to reflect the
               Exchange Ratio.


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                             (d) If your option was originally designated in
               your Option Agreement as an Incentive Stock Option, your option
               as assumed by Cisco shall remain an Incentive Stock Option to the
               maximum extent allowed by law.

                             (e) For purposes of applying any and all provisions
               of the Option Agreement and/or the Plan relating to Optionee's
               status as an employee, consultant, or director of V-Bits,
               Optionee shall be deemed to continue in such status as an
               employee, consultant, or director for so long as Optionee renders
               services as an employee, consultant, or director to Cisco or any
               present or future Cisco subsidiary. Accordingly, the provisions
               of the Option Agreement governing the termination of the assumed
               V-Bits Options upon Optionee's cessation of service as an
               employee, consultant, or director of V-Bits shall hereafter be
               applied on the basis of Optionee's cessation of employee,
               consultant, or director status with Cisco and its subsidiaries,
               and each assumed V-Bits Option shall accordingly terminate,
               within the designated time period in effect under the Option
               Agreement for that option, generally a one (1)-month period,
               following such cessation of service as an employee, consultant,
               or director of Cisco and its subsidiaries.

                             (f) The adjusted exercise price payable for the
               Cisco Stock subject to each assumed V-Bits Option shall be
               payable in any of the forms authorized under the Option Agreement
               applicable to that option. For purposes of determining the
               holding period of any shares of Cisco Stock delivered in payment
               of such adjusted exercise price, the period for which such shares
               were held as V-Bits Stock prior to the Merger shall be taken into
               account.

                             (g) In order to exercise each assumed V-Bits
               Option, Optionee must deliver to Cisco a written notice of
               exercise in which the number of shares of Cisco Stock to be
               purchased thereunder must be indicated. The exercise notice must
               be accompanied by payment of the adjusted exercise price payable
               for the purchased shares of Cisco Stock and should be delivered
               to Cisco at the following address:

                             Cisco Systems, Inc.
                             170 West Tasman Drive
                             MS 11-3
                             San Jose, CA 95134
                             Attention: Stock Administration

               4. Except to the extent specifically modified by this Option
Assumption Agreement, all of the terms and conditions of each Option Agreement
as in effect immediately prior to the Merger shall continue in full force and
effect and shall not in any way be amended, revised or otherwise affected by
this Stock Option Assumption Agreement.

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                                                            PARTIAL ACCELERATION

               IN WITNESS WHEREOF, Cisco Systems, Inc. has caused this Stock
Option Assumption Agreement to be executed on its behalf by its duly authorized
officer as of the 6th day of December, 1999.




                                            CISCO SYSTEMS, INC.

                                            By: /s/ LARRY R. CARTER
                                               ---------------------------------
                                                 Larry R. Carter
                                                 Corporate Secretary


                                 ACKNOWLEDGMENT


               The undersigned acknowledges receipt of the foregoing Stock
Option Assumption Agreement and understands that all rights and liabilities with
respect to each of his or her V-Bits Options hereby assumed by Cisco are as set
forth in the Option Agreement, the Plan, as applicable, and such Stock Option
Assumption Agreement.


                                            ------------------------------------
                                            [FIRST_NAME] [LAST_NAME], OPTIONEE



DATED:  __________________, 1999


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