Document:

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                                                                     Exhibit 4.1

                           INDUS RIVER NETWORKS, INC.
                             STOCK INCENTIVE PROGRAM

     1.   PURPOSE. The purpose of the Indus River Networks, Inc. Stock Incentive
Program (the "Plan") is to provide incentives which will attract and retain
highly competent persons as officers, key employees, directors and consultants
of Indus River Networks, Inc. (the "Company") and its subsidiary corporations by
providing them opportunities to acquire shares of the Company's common stock,
$0.01 par value per share ("Common Shares") or to receive monetary payments
based on the value of such stock. Except where the context otherwise requires,
the term "Company" shall include all present and future subsidiaries of the
Company as defined in Sections 424(e) and 424(f) of the Internal Revenue Code of
1986, as amended (the "Code").

     2.   ADMINISTRATION. The Plan will be administered by the Board of
Directors of the Company (the "Board"). The Board is authorized, subject to the
provisions of the Plan, to establish such rules and regulations as it deems
necessary for the proper administration of the Plan and to make such
determinations and interpretations and to take such action or inaction in
connection with the Plan and any benefits granted hereunder as it deems
necessary or advisable. All determinations and interpretations made by the Board
shall be binding and conclusive on all participants and their legal
representatives. The Board may correct any defect or supply any omission or
reconcile any inconsistency in the Plan or in any related agreement in the
manner and to the extent it shall deem expedient to effectuate the purposes of
the Plan. No member of the Board, and no officer or employee of the Company,
shall be liable for any act or failure to act hereunder, by any other member of
the Board or any officer or employee or by any agent to whom duties in
connection with the administration of this Plan have been delegated or, except
in circumstances involving his bad faith, gross negligence or fraud, for any act
or failure to act by the member of the Board or any officer or employee.

     3.   SHARES RESERVED UNDER THE PLAN. There is hereby reserved for issuance
under the Plan an aggregate of 4,209,500 Common Shares, which may be authorized
but unissued or treasury shares. All of such shares may, but need not, be issued
pursuant to the exercise of Incentive Stock Options. If there is a lapse,
expiration, termination or cancellation of any Incentive Stock Option,
Nonqualified Stock, Option, Stock Appreciation Right or Performance Share prior
to the issuance of shares thereunder, or if Common Shares are issued under a
Stock Option or Stock Appreciation Right or as Restricted Stock or Performance
Shares and thereafter are reacquired by the Company pursuant to rights reserved
upon issuance thereof, those shares may again be used for new benefits under
this Plan.

     4.   PARTICIPANTS. Participants will consist of such officers, key
employees, directors and consultants of the Company as the Board, in its sole
discretion, determines to be significantly responsible for the success and
future growth and profitability of the Company. Designation of a participant in
any year shall not require the Board to designate such person to receive a
benefit in any other year or to receive the same type or amount of benefit as
granted to the participant in any other year or as granted to any other
participant in any year. The Board shall consider such factors as it deems
pertinent in selecting participants and in determining the type and amount of
their respective benefits.

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     5.   TYPES OF BENEFITS. Benefits under the Plan may be granted by the Board
in its sole discretion in any one or a combination of (a) Stock Options (b)
Stock Appreciation Rights; (c) Restricted Stock; and (d) Performance Shares, all
as hereinafter described.

     6.   STOCK OPTIONS. Stock Options will consist of awards from the Company,
in the form of agreements, which will enable the holder to purchase a specific
number of Common Shares, at set terms and at a fixed purchase price. Stock
Options may be "incentive stock options" within the meaning of Section 422 of
the Code ("Incentive Stock Options") or Stock Options which do not constitute
Incentive Stock Options ("Nonqualified Stock Options"). The Board will have the
authority to grant to any participant one or more Incentive Stock Options,
Nonqualified Stock Options, or both types of Stock Options. Each Stock Option
shall be subject to such terms and conditions consistent with the Plan as the
Board may impose from time to time, subject to the following limitations:

          (a) Exercise Price. Subject to Paragraph (e) below, each Stock Option
granted hereunder shall have such per-share exercise price as the Board may
determine at the date of grant.

          (b) Payment of Exercise Price. Options granted under the Plan may
provide for the payment of the exercise price by delivery of cash or a check to
the order of the Company in an amount equal to the exercise price of such
options, or by delivery to the Company of Common Shares already owned by the
participant having a Fair Market Value equal in amount to the exercise price of
the options being exercised or by any combination of such methods of payment.
The Fair Market Value of any Common Shares which may be delivered upon exercise
of an option shall be determined by the Board.

          (c) Exercise Period. Stock Options granted under the Plan shall be
exercisable at such times and subject to such terms and conditions as shall be
determined by the Board. In addition, Stock Options shall not be exercisable
more than ten years after the date they are granted. All Stock Options shall
terminate at such earlier times and upon such conditions or circumstances as the
Board shall in its discretion set forth in such option at the date of grant.

          (d) Exercise of Options. Each option granted under the Plan shall be
exercisable either in full or in installments at such time or times and during
such period as shall be set forth in the agreement evidencing such option,
subject to the provisions of paragraph (c) above. To the extent that an option
to purchase Common Shares is not exercised by an optionee when it becomes
initially exercisable, it shall not expire but shall be carried forward and
shall be exercisable, on a cumulative basis, until the expiration of the
exercise period.

          (e) Limitations on Incentive Stock Options. Incentive Stock Options
may be granted only to participants who are employees of the Company at the date
of grant. The aggregate Fair Market Value (determined as of the time the option
is granted) of the Common Shares with respect to which Incentive Stock Options
are exercisable for the first time by a participant during any calendar year
(under all option plans of the Company) shall not exceed $100,000. Incentive
Stock Options may not be granted to any participant who, at the time of grant,
owns stock possessing (after the application of the attribution rules of Section
424(d) of the Code) more than 10% of the total combined voting power of all
classes of stock of the Company, unless the option price is fixed at not less
than 110% of the Fair Market Value of the

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Common Shares on the date of grant and the exercise of such option is prohibited
by its terms after the expiration of five years from the date of grant of such
option.

          (f) Redesignation as Nonqualified Stock Options. Options designated as
Incentive Stock Options that fail to continue to meet the requirements of
Section 422 of the Code shall be redesignated as nonqualified options for
Federal income tax purposes automatically without further action by the Board on
the date of such failure to continue to meet the requirements of Section 422 of
the Code.

          (g) Limitation of Rights in Common Shares. The recipient of a Stock
Option shall not be deemed for any purpose to be a shareholder of the Company
with respect to any of the shares subject thereto except to the extent that the
Stock Option shall have been exercised and, in addition, a certificate shall
have been issued and delivered to the participant.

     7.   STOCK APPRECIATION RIGHTS. The Board may, in its discretion, grant a
Stock Appreciation Right in connection with any Stock Option granted hereunder.
Each Stock Appreciation Right shall be subject to such terms and conditions
consistent with the Plan as the Board shall determine from time to time,
including the following:

          (a) A Stock Appreciation Right may be made part of a Stock Option at
the time of its grant or at any time thereafter up to six months prior to its
expiration.

          (b) Each Stock Appreciation Right will entitle the holder to elect to
receive, in lieu of exercising the Stock Option to which it relates, an amount
(in cash or in Common Shares, or a combination thereof, all in the sole
discretion of the Board) equal to 100% of the excess of:

               (i) the Fair Market Value per Common Share on the date of
exercise of such right, multiplied by the number of shares with respect to which
the right is being exercised, over

               (ii) the aggregate option price for such number of shares.

          (c) Each Stock Appreciation Right will be exercisable at the time and
to the extent the Stock Option to which it relates is exercisable.

          (d) Upon exercise of a Stock Appreciation Right, the Stock Option (or
portion thereof) with respect to which such right is exercised shall be
surrendered and shall not thereafter be exercisable.

          (e) Exercise of a Stock Appreciation Right will reduce the number of
shares purchasable pursuant to the related option and available for issuance
under the Plan to the extent of the number of shares with respect to which the
right is exercised, whether or not any portion of the payment made upon exercise
of such right is made in Common Shares

     8.   RESTRICTED STOCK. Restricted Stock awards will consist of Common
Shares transferred to participants without other payment therefor as additional
compensation for their services to the Company. Restricted Stock awards shall be
subject to such terms and conditions as the Board determines appropriate,
including, without limitation, restrictions on

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the sale or other disposition of such shares and rights of the Company to
reacquire such shares upon termination of the participant's employment within
specified periods.

     9.   PERFORMANCE SHARES. Performance Shares shall consist of shares of
Common Shares which may be earned in whole or in part of certain goals
established by the Board are achieved over a period of time established by the
Board, but not in any event more than five years. The goals established by the
Board may include return on equity, earnings per share and such other
corporation, divisional, personal or other goals as may be established by the
Board in its discretion. In the event the minimum goal is not achieved at the
conclusion of the period, no delivery of shares shall be made to the
participant. In the event the maximum goal is achieved, 100% of the Performance
Shares corresponding to the degree of achievement as determined by the Board.
The Board shall have the discretion to satisfy a participant's Performance
Shares by delivery of less than the number of shares earned together with a cash
payment equal to the then value of the shares not delivered, but in any case
other than death, disability or retirement no more than 50% of the total award
earned may be paid in cash. The number of shares reserved for issuance hereunder
shall be reduced by the number of Performance Shares earned even though a
portion of the award is paid in cash.

     10.  ADJUSTMENT PROVISIONS.

          (a) If the Company shall at any time change the number of issued
Common Shares without new consideration to the Company (such as by stock
dividend, stock split, recapitalization, reorganization, exchange of shares,
liquidation, combination or other change in corporate structure), the total
number of shares reserved for issuance under this Plan and the number of shares
covered by each outstanding benefit shall be adjusted so that the aggregate
consideration payable to the Company, if any, shall not be changed.

          (b) Notwithstanding any other provision of this Plan, and without
affecting the number of shares reserved or available hereunder, the Board of
Directors may authorize the issuance or assumption of benefits in connection
with any merger, consolidation, acquisition of property or stock, or
reorganization upon such terms and conditions as it may deem appropriate.

          (c) In the case of any merger, consolidation or combination of the
Company with or into another corporation, other than a merger, consolidation or
combination in which the Company is the continuing corporation and which does
not result in the outstanding Common Shares being converted into or exchanged
for different securities, cash or other property, or any combination thereof (an
"Acquisition").

               (i) any participant to whom a stock option has been granted under
the Plan shall have the right (subject to the provisions of the Plan and any
limitation applicable to such option) thereafter and during the term of such
option, to receive upon exercise thereof the Acquisition Consideration
receivable upon such Acquisition by a holder of the number of Common Shares
which might have been obtained upon exercise of such options or portion thereof,
as the case may be, immediately prior to such Acquisition;

               (ii) any participant to whom a Stock Appreciation Right has been
granted under the Plan shall have the right (subject to the provisions of the
Plan and any limitation applicable to such right) thereafter and during the term
of such right to receive upon

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exercise thereof the difference between the aggregate Fair Market Value on the
applicable date (as set forth in such right) of the Acquisition Consideration
receivable upon such Acquisition by a holder of the number of Common Shares
which might have been obtained upon exercise of the option related thereto or
any portion thereof, as the case may be, immediately prior to such Acquisition
and the aggregate option price of such option or portion thereof; and

               (iii) any participant to whom a Performance Share award has been
granted under the Plan shall have the right (subject to the provisions of the
plan and any limitations applicable to such award) thereafter and during the
term of such award to receive on the date set forth in such award, the
Acquisition Consideration receivable upon such Acquisition by a holder of the
number of Common Shares which are covered by such award.

     The term "Acquisition Consideration" shall mean the kind and amount of
     shares of the surviving or new corporation, cash, securities, evidence of
     indebtedness, other property or any combination thereof receivable in
     respect of one Common Share upon consummation of an Acquisition.

     11.  NONTRANSFERABILITY. Each benefit granted under the Plan to an employee
shall not be transferable otherwise than by will or the laws of descent and
distribution, and shall be exercisable, during the participant's lifetime, only
by the participant. In the event of the death of a participant exercise or
payment shall be made only:

          (a) by or to the executor or administrator of the estate of the
deceased participant or the person or persons to whom the deceased participant's
rights under the benefit shall pass by will or the laws of descent and
distribution; and

          (b) To the extent that the deceased participant was entitled thereto
at the date of his death.

     12.  OTHER PROVISIONS. Benefits granted under the Plan may also be subject
to such other provisions (whether or not applicable to any other benefits under
the Plan) as the Board, in its sole discretion, determines appropriate,
including without limitation, provisions determining the effect that a
termination of employment shall have on the participant's benefits, provisions
for the installment purchase of Common Shares, provisions to assist the
participant in financing the acquisition of Common Shares, provisions for the
forfeiture of, or restrictions on resale or other disposition of Common Shares
acquired under any form of benefit hereunder, provisions for the acceleration of
exercisability or vesting of benefits in the event of a change of control of the
Company, provisions for the payment of the value of benefits to participants in
the event of a change of control of the Company, provisions for the forfeiture
of, or provisions to comply with Federal and state securities laws, or
understandings or conditions as to the participant's employment in addition to
those specifically provided for under the Plan. Notwithstanding the foregoing,
such additional provisions shall not cause any Incentive Stock Option granted
under the Plan to fail to qualify as an Incentive Stock Option within the
meaning of Section 422 of the Code.

     13.  FAIR MARKET VALUE. For purposes of this Plan and any benefits granted
hereunder, the Fair Market Value of Common Shares shall be the amount determined
in good faith by the Board from time to time as the fair market value of the
Common Shares.

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     14.  WITHHOLDING. The Company shall be entitled to withhold the amount of
any tax attributable to any amounts payable or shares deliverable under the Plan
after giving the person entitled to receive such payment or delivery reasonable
notice, and the Company may defer making payment or delivery as to any benefit
if any such tax is payable until indemnified to its satisfaction. The Board may,
in its discretion and subject to such rules as it may adopt, permit a
participant to pay all or a portion of the federal, state and local withholding
taxes arising in connection with (a) the exercise of an Incentive Stock Option,
(b) a disqualifying disposition of Common Shares received upon the exercise of
an Incentive Stock Option, (c) the lapse of restrictions on shares received as
Restricted Stock or (d) receipt of Performance Shares, by electing to (i) have
the Company withhold Common Shares, (ii) tender back Common Shares received in
connection with such benefit, or (iii) deliver other previously owned Common
Shares, having a Fair Market Value equal to the amount to be withheld; provided,
however that the amount to be withheld shall not exceed the participant's
estimated total federal, state and local tax obligations associated with the
transaction. The election must be made on or before the date as of which the
amount of tax to be withheld is determined (the "Tax Date"). The Fair Market
Value of the Common Shares used to pay withholding taxes is the average of the
high and low price of the Common Shares on the tax date. The Fair Market Value
of fractional shares remaining after payment of the withholding taxes shall be
paid to the participant in cash.

     15.  RIGHTS AS A SHAREHOLDER. The holder of any benefit under this Plan
shall have no rights as a shareholder with respect to any Common Shares covered
by such benefit (including, without limitation, any rights to receive dividends
or non-cash distributions with respect to such shares) until the date of issue
of a stock certificate to him or her for such shares. No adjustment shall be
made for dividends or other rights for which the record date is prior to the
date such stock certificate is issued.

     16.  TENURE. A participant's right, if any, to continue to serve the
Company as an officer, employee, or otherwise, shall not be enlarged or
otherwise affected by his designation as a participant under the Plan, nor shall
this Plan in any way interfere with the right of the Company, subject to the
terms of any separate employment agreement to the contrary, at any time to
terminate such employment or to increase or decrease the compensation of the
participant from the rate in existence at the time of the grant of a Stock
Option. Whether an authorized leave of absence, or absence in military or
government service, shall constitute termination of employment shall be
determined by the Board at the time.

     17.  OTHER EMPLOYEE BENEFITS. The amount of any compensation that may be
deemed to be received by an participant as a result of the grant of Stock
Options, Restricted Stock, Performance Shares or Stock Appreciation Rights shall
not constitute compensation with respect to which any other participant benefits
of such employee are determined, including, without limitation, benefits under
any bonus, pension, profit sharing, life insurance or salary continuation plan,
unless separate provision to the contrary is contained in such other plan.

     18.  DURATION, AMENDMENT AND TERMINATION. No stock option or other benefit
shall be granted more than ten years after the date of adoption of this Plan;
provided, however, that the terms and conditions applicable to any option or
benefit granted within such period may thereafter be amended or modified by
mutual agreement between the Company and the participant or such other persons
as may then have an interest therein. Also, by mutual agreement between the
Company and a participant hereunder or under any other stock option

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plan of the Company, options or rights may be granted to such participant in
substitution and exchange for, and in cancellation of, any benefits previously
granted such participant under this Plan or any other stock option plan of the
Company. The Board may amend the Plan from time to time or terminate the Plan at
any time. However, no action authorized by this paragraph shall reduce the
amount of any existing benefit or change the terms and conditions thereof
without the participant's consent. No amendment of the Plan shall, without
approval of the shareholders of the Company, (a) materially increase the total
number of shares which may be issued under the Plan, (b) materially reduce the
minimum purchase price of Common Shares which may be made subject to benefits
under the Plan; or (c) materially modify the requirements as to eligibility for
benefits under the Plan.

     19.  GOVERNING LAW. This Plan and actions taken in connection herewith
shall be governed and construed in accordance with the laws of The Commonwealth
of Massachusetts (regardless of the law that might otherwise govern under
applicable Massachusetts principles of conflict of laws).

     20.  SHAREHOLDER APPROVAL. The Plan was adopted by the Board of Directors
on April 1, 1997, subject to shareholder approval. The Plan and any benefits
granted thereunder shall be null and void if shareholder approval is not
obtained within twelve months of the adoption of the Plan by the Board of
Directors. The number of Common Shares reserved for issuance under the Plan was
increased to 2,709,500 by virtue of written consents of the Board of Directors
and shareholders of the Company dated June 15, 1998, to 3,209,500 by virtue of
written consents of the Board of Directors and shareholders dated June 30, 1999
and to 4,209,500 by virtue of written consents of the Board of Directors and
shareholders dated April 27, 2000.

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                                                                     Exhibit 4.2

                                                         STOCK INCENTIVE PROGRAM

                        FORM OF CABLETRON SYSTEMS, INC.
                       STOCK OPTION ASSUMPTION AGREEMENT

OPTIONEE:

     STOCK OPTION ASSUMPTION AGREEMENT issued as of the 31st day of January,
2001 by Cabletron Systems, Inc., a Delaware corporation ("Cabletron").

     WHEREAS, _____________ ("Optionee") holds one or more outstanding options
to purchase shares of the common stock of Indus River Networks, Inc., a Delaware
corporation ("Indus River"), which were granted to Optionee under Indus River's
Stock Incentive Program (the "Plan"), and are evidenced by a Stock Option
Agreement [, as amended by an Option Modification Agreement](1) (the "Option
Agreement") between Indus River and Optionee.

     WHEREAS, Indus River has been acquired as of January 31, 2001 by Cabletron
through merger of a wholly owned Cabletron subsidiary, Acton Acquisition, Co.
("Merger Sub"), with and into Indus River (the "Merger") pursuant to the
Agreement and Plan of Merger dated as of August 18, 2000, as amended as of
December 3, 2000, by and among Cabletron, Indus River and Merger Sub (the
"Merger Agreement").

     WHEREAS, the provisions of the Merger Agreement require Cabletron to assume
all obligations of Indus River under all options outstanding under the Plan upon
the consummation of the Merger (the "Indus River Options") and to issue to the
holder of each outstanding Indus River Option a notice setting forth such
holder's rights after consummation of the Merger.

     WHEREAS, pursuant to the provisions of the Merger Agreement, Optionee's
Indus River Options now represent options ("Cabletron Options") to purchase
shares of Cabletron Common Stock, $.01 par value, ("Cabletron Common Stock") and
Cabletron Series C Participating Convertible Preferred Stock, $1.00 par value,
("Cabletron Series C Preferred Stock," and together with the Cabletron Common
Stock, the "Cabletron Stock").

     WHEREAS, the number of shares of Cabletron Common Stock which are subject
to Optionee's Cabletron Options is equal to the number of shares of Indus River
common stock otherwise purchasable pursuant to such options multiplied by the
exchange ratio of 0.16590692 (the "Common Exchange Ratio"), rounded down to the
nearest whole number, at an exercise price per share equal to the exercise price
per share of such Indus River common stock multiplied by 4.62876672, rounded up
to the next highest cent, and the number of shares of Cabletron Series C
Preferred Stock which are subject to Optionee's Cabletron Options is equal to
the number of shares of Indus River common stock otherwise purchasable pursuant
to such

--------
(1) Only insert this language if applicable.

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options multiplied by the exchange ratio of 0.00207384 (the "Preferred Exchange
Ratio"), rounded down to the nearest whole number, at an exercise price per
share equal to the exercise price per share of such Indus River common stock
multiplied by 111.89655904, rounded up to the next highest cent.

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

     NOW, THEREFORE, it is hereby agreed as follows:

     1. The number of shares of Indus River common stock subject to the Indus
River Options held by Optionee under the Plan immediately prior to the Effective
Time and the exercise price payable per share are set forth in EXHIBIT A hereto.
Cabletron hereby assumes, as of the Effective Time, all the duties and
obligations of Indus River under each of the Indus River Options. In connection
with such assumption, the number of shares of Cabletron Common Stock and
Cabletron Series C Preferred Stock purchasable under each Indus River Option
hereby assumed and the exercise price payable thereunder have been adjusted to
reflect the Common Exchange Ratio and the Preferred Exchange Ratio,
respectively, at which shares of Indus River common stock purchasable under
Optionee's Indus River Options were converted into shares of Cabletron Common
Stock and Cabletron Series C Preferred Stock purchasable under Optionee's
Cabletron Options upon consummation of the Merger. Accordingly, the number of
shares of Cabletron Common Stock and Cabletron Series C Preferred Stock subject
to each Indus River Option hereby assumed, and the adjusted exercise price
payable per share of Cabletron Stock under the assumed Indus River Option, shall
be as indicated for that option in attached EXHIBIT B.

     2. The intent of the foregoing adjustments to each assumed Indus River
Option is to assure that the spread between the aggregate fair market value of
the shares of Cabletron Common Stock and Cabletron Series C Preferred Stock
purchasable under that option and the aggregate exercise price as adjusted
hereunder will, immediately after the consummation of the Merger, equal the
spread which existed, immediately prior to the Merger, between the then
aggregate fair market value of the Indus River common stock subject to the Indus
River Option and the aggregate exercise price in effect at such time under the
Option Agreement. Such adjustments are also designed to preserve, on a per share
basis immediately after the Merger, the same ratio of exercise price per option
share to fair market value per share which existed under the Indus River Option
immediately prior to the Merger.

     3. The following provisions shall govern each Indus River Option hereby
assumed by Cabletron:

     - Unless the context otherwise requires, all references to the "Company" in
each Option Agreement and in the Plan (as incorporated into such Option
Agreement) shall mean Cabletron (except with respect to any provisions related
to a "Change of Control", as such term is defined in each Option Agreement), all
references to "Common Shares" shall mean shares of Cabletron

<PAGE>   3

Common Stock or Cabletron Series C Preferred Stock, as the case may be, and all
references to the "Board" shall mean the Incentive Compensation Committee of the
Board of Directors of Cabletron.

     - The grant date and the expiration date of each assumed Indus River Option
and all other provisions which govern either the exercisability or the
termination of the assumed Indus River Option shall remain the same as set forth
in the Option Agreement applicable to that option and shall accordingly govern
and control Optionee's rights under this Agreement to purchase Cabletron Stock.

     - Each Cabletron Option shall remain exercisable in accordance with the
same installment exercise schedule in effect under the applicable Option
Agreement to which such Cabletron Option relates immediately prior to the
Effective Time (subject to any applicable acceleration provisions), with the
number of shares of Cabletron Common Stock and Cabletron Series C Preferred
Stock subject to each such installment adjusted to reflect the Common Exchange
Rate and the Preferred Exchange Rate, respectively. The grant date for each
assumed Indus River Option shall accordingly remain the same as in effect under
the applicable Option Agreement immediately prior to the Merger.

     - For purposes of applying any and all provisions of the Option Agreement
relating to Optionee's status as an employee with the Company, Optionee shall be
deemed to continue in such employee status for so long as Optionee renders
services as an employee to Cabletron or any present or future Cabletron
subsidiary, including (without limitation) Indus River, provided however, that
if the entity for which Optionee renders services as an employee ceases to be a
subsidiary of Cabletron, Optionee's status as an employee will be deemed
terminated at the time that such entity ceases to be a subsidiary of Cabletron.
Accordingly, the provisions of the Option Agreement governing the termination of
the assumed Indus River Option upon the Optionee's cessation of employee status
with Indus River shall hereafter be applied on the basis of the Optionee's
cessation of employee status with Cabletron and its subsidiaries, and each
assumed Indus River Option shall accordingly terminate, within the designated
time period in effect under the Option Agreement for that option, following such
cessation of employment with Cabletron and its subsidiaries.

     - The adjusted exercise price payable for the Cabletron Stock subject to
each assumed Indus River 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 Cabletron Stock delivered in
payment of such adjusted exercise price, the period for which such shares were
held as Indus River common stock prior to the Merger shall be taken into
account.

     - If Optionee exercises any assumed Cabletron Option with respect to shares
of Cabletron Series C Preferred Stock prior to July 31, 2002, the stock
certificates evidencing the Series C Preferred Stock purchased upon such
exercise shall be delivered to State Street Bank and Trust Company ("State
Street") and held in escrow pursuant to the terms of that certain Escrow
Agreement dated as of January 31, 2001 ("Escrow Agreement") by and among
Cabletron, State Street, as escrow agent, and Steven J. Ricci, as representative
of the

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stockholders of Indus River, and such shares of Series C Preferred Stock shall
be deemed to be Parent Preferred Escrow Shares (as that term is defined in the
Escrow Agreement), and subject to the provisions of the Escrow Agreement.

     3. Except to the extent specifically modified by this Stock 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.

     IN WITNESS WHEREOF, Cabletron Systems, Inc. has caused this Stock Option
Assumption Agreement to be executed on its behalf by its duly-authorized officer
as of the 31st day of January, 2001.

                                               CABLETRON SYSTEMS, INC.

                                               By:______________________________

<PAGE>   5

                                    EXHIBIT A

 Optionee's Outstanding Options to Purchase Shares of Indus River Networks, Inc.
                            Common Stock (Pre-Merger)

<PAGE>   6

                                    EXHIBIT B

  Optionee's Outstanding Options to Purchase Shares of Cabletron Systems, Inc.
             Common Stock and Series C Preferred Stock (Post-Merger)

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