EXHIBIT 10.20

                             ----------------------
                            STOCK PURCHASE AGREEMENT

                                December 12, 1996
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                                TABLE OF CONTENTS

                                                                          Page
                                                                          ----

1.       Purchase and Sale of Stock........................................  1
         1.1      Closing..................................................  1
         1.2      Delivery.................................................  1

2.       Representations and Warranties of the Company.....................  1
         2.1      Authority................................................  1
         2.2      Organization, Good Standing and Qualification............  2
         2.3      Capitalization and Voting Rights.........................  3
         2.4      Subsidiaries.............................................  3
         2.5      Valid Issuance of Common Stock...........................  3
         2.6      Governmental Consents....................................  4
         2.7      Offering.................................................  4
         2.8      Litigation...............................................  4
         2.9      Intellectual Property....................................  4
         2.10     Conflicts................................................  5
         2.11     Compliance with Other Instruments........................  5
         2.12     Disclosure...............................................  6
         2.13     Registration Rights......................................  6
         2.14     Title to Property and Assets.............................  6
         2.15     Financial Statements.....................................  6
         2.16     Changes..................................................  6
         2.17     SEC Documents; Material Contracts........................  7
         2.18     Compliance with All Laws.................................  7
         2.19     Investment Company.......................................  8

3.       Representations and Warranties of Investor........................  8
         3.1      Authorization............................................  8
         3.2      Purchase Entirely for Own Account........................  8
         3.3      Governmental Consents....................................  8
         3.4      No Consent...............................................  8
         3.5      Disclosure of Information................................  9
         3.6      Investment Experience....................................  9
         3.7      Accredited Investor......................................  9
         3.8      Restricted Securities....................................  9
         3.9      Further Limitations on Disposition.......................  9
         3.10     Legends.................................................. 10

4.       Right to Notification............................................. 10
         4.1      Notification of Acquisition of Securities................ 10

                                       i.

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         4.2      Notification of Receipt of Acquisition Proposal
                     or Initiation of Sale................................. 10
         4.3      Actual Voting Power...................................... 11

5.       Registration Rights............................................... 11
         5.1      Request for Registration................................. 11
         5.2      Obligations of the Company............................... 12
         5.3      Expenses of Registration................................. 14
         5.4      Indemnification.......................................... 14
         5.5      Limitations on Subsequent Registration Rights............ 16

6.       Right of First Offer.............................................. 17
         6.1      New Issuances............................................ 17
         6.2      "New Securities"......................................... 17
         6.3      Notice of New Securities................................. 17
         6.4      Exercise of Right of First Offer......................... 18
         6.5      Transferability.......................................... 18
         6.6      Closing.................................................. 18
         6.7      Reservation of Shares.................................... 18
         6.8      Term..................................................... 18

7.       Conditions of Investor's Obligations at Closing................... 18
         7.1      Representations and Warranties........................... 19
         7.2      Performance.............................................. 19
         7.3      Compliance Certificate................................... 19
         7.4      Qualifications........................................... 19
         7.5      Proceedings and Documents................................ 19
         7.6      Opinion of Company Counsel............................... 19

8.       Conditions of the Company's Obligations at Closing................ 19
         8.1      Representations and Warranties........................... 19
         8.2      Payment of Purchase Price................................ 19
         8.3      Qualifications........................................... 20

9.       Investor Notice................................................... 20

10.      Miscellaneous..................................................... 21
         10.1     Survival of Warranties................................... 21
         10.2     Assignment; Successors and Assigns....................... 21
         10.3     Governing Law............................................ 21
         10.4     Counterparts............................................. 21
         10.5     Titles and Subtitles..................................... 22
         10.6     Notices, etc............................................. 22
         10.7     Finder's Fee............................................. 23
         10.8     Expenses................................................. 23

                                       ii.
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10.9     Amendments and Waivers............................................ 23
10.10    Severability...................................................... 23
10.11    Entire Agreement.................................................. 23




                                      iii.

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                            STOCK PURCHASE AGREEMENT


                  THIS STOCK PURCHASE  AGREEMENT (the "Agreement") is made as of
the 12th day of December,  1996, by and among Interlink Computer Sciences, Inc.,
a Delaware  corporation (the "Company"),  and Cisco Systems,  Inc., a California
corporation ("Investor").

                  WHEREAS,  the  Company and  Investor  have agreed to execute a
Binding Letter of Intent contemporaneously with this Agreement;

                  WHEREAS, pursuant to the Binding Letter of Intent, the parties
have  agreed  that  they will  execute  a  Development,  Marketing  and  Support
Agreement  no later than  January 16,  1997,  which will  supersede  the Binding
Letter of Intent; and

                  WHEREAS,  this Agreement  supersedes Section 15 and Section 17
of the Binding Letter of Intent.

                  THE PARTIES HEREBY AGREE AS FOLLOWS:

                  1.  Purchase  and Sale of  Stock.  Subject  to the  terms  and
conditions  of this  Agreement,  Investor  agrees to purchase at the Closing (as
hereinafter defined) and the Company agrees to sell and issue to Investor at the
Closing,  622,000  shares of the  Company's  Common Stock (the  "Shares"),  at a
purchase price of eleven dollars ($11.00) per share (the "Purchase Price").

                  1.1 Closing. The purchase and sale of the Shares shall be held
at the offices of Wilson,  Sonsini,  Goodrich & Rosati, 650 Page Mill Road, Palo
Alto,  California,  on December 12, 1996 at 4:00 p.m., or at such other time and
place upon which the Company  and  Investor  shall  agree  (which time and place
shall be referred to as the "Closing").

                  1.2  Delivery.  At the  Closing,  the  Company  will  issue to
Investor a  certificate  registered in the  Investor's  name,  representing  the
number of Shares  purchased by Investor  against  payment of the Purchase Price.
The Purchase  Price shall be paid to the Company by certified  check  payable to
the Company or by wire transfer.

                  2.  Representations and Warranties of the Company. The Company
hereby represents and warrants to Investor that:

                  2.1  Authority.  The Company has full power and  authority  to
execute  and  deliver  this  Agreement,   and  to  consummate  the  transactions
contemplated by this Agreement. All corporate action on the part of the Company,
its  officers,  directors  and  stockholders  necessary  for the  execution  and
delivery of, and the consummation of the

<PAGE>

transactions   contemplated  by  this  Agreement  and  the  performance  of  all
obligations of the Company under this Agreement has been taken.  This Agreement,
upon  execution  and  delivery by the Company  and  assuming  the due and proper
execution  and  delivery  by  Investor,  constitutes  legal,  valid and  binding
obligations of the Company, enforceable in accordance with its respective terms,
except  as  may  be   limited   by  (i)   applicable   bankruptcy,   insolvency,
reorganization or other laws of general application relating to or affecting the
enforcement of creditors rights  generally,  and (ii) the effect of rules of law
governing the availability of equitable remedies.  The making and performance of
this Agreement by the Company and the  consummation of the  transactions  herein
contemplated will not violate any provisions of the certificate of incorporation
or  bylaws,  or other  organizational  documents,  of the  Company or any of its
subsidiaries,  and will not conflict with, result in the breach or violation of,
or constitute, either by itself or upon notice or the passage of time or both, a
default under any material agreement, mortgage, deed of trust, lease, franchise,
license,  indenture,  permit or other  instrument to which the Company or any of
its  subsidiaries is a party or by which the Company or any of its  subsidiaries
or any of its respective properties may be bound or affected, any statute or any
authorization,  judgment,  decree, order, rule or regulation of any court or any
regulatory body,  administrative agency or other governmental body applicable to
the Company or any of its subsidiaries or any of their respective properties.

                  2.2 Organization, Good Standing and Qualification. The Company
and  each of its  subsidiaries  have  been  duly  incorporated  and are  validly
existing as  corporations  in good standing  under the laws of their  respective
jurisdictions  of  incorporation,  with full power and authority  (corporate and
other) to own and lease their properties and conduct their respective businesses
and all proposed  future  businesses.  With the  exception of Interlink  Iberica
S.A., of which the Company owns 99.8% of the  outstanding  capital  stock;  each
subsidiary  of the Company  only has one class of capital  stock and the Company
owns all of the outstanding  capital stock of its subsidiaries free and clear of
all  claims,  liens,  charges  and  encumbrances;  the  Company  and each of its
subsidiaries  are  in  possession  of  and  operating  in  compliance  with  all
authorizations, licenses, permits, consents, certificates and orders material to
the conduct of their respective  businesses,  all of which are valid and in full
force and effect,  except where the failure of any such authorization,  license,
permit, consent, certificate or order to be valid or in full force, would not in
any single case or when aggregated with all such failures by the Company and all
of its subsidiaries have a material adverse effect upon the Company; the Company
and each of its  subsidiaries  are duly  qualified  to do  business  and in good
standing as foreign  corporations in each jurisdiction in which the ownership or
leasing of properties  or the conduct of their  respective  businesses  requires
such qualification,  except for jurisdictions in which the failure to so qualify
would not have a material  adverse effect upon the Company and its  subsidiaries
taken  as  a  whole;   and  no  proceeding  has  been  instituted  in  any  such
jurisdiction,  revoking,  limiting or curtailing, or seeking to revoke, limit or
curtail, such power and authority or qualification.

                                       2.
<PAGE>

                  2.3  Capitalization  and Voting Rights. The authorized capital
of the Company as of December 3, 1996 consisted of:

                         (i)  Preferred  Stock.  5,000,000  shares of  Preferred
Stock,  $0.001 par value (the "Preferred  Stock"),  none of which are issued and
outstanding.

                         (ii) Common Stock.  25,000,000  shares of common stock,
$0.001 par value  ("Common  Stock"),  of which  6,388,789  shares are issued and
outstanding.

                         (iii)  Other  than  2,105,000  shares of  Common  Stock
reserved for issuance to employees  pursuant to the Company's  1992 Stock Option
Plan (the "Option  Plan"),  of which options to purchase  1,335,310  shares have
been granted,  350,000  shares of Common Stock  reserved for issuance  under the
1996 Employee Stock Purchase Plan (the "Purchase Plan"), of which no shares have
been  issued,  150,000  shares of Common Stock  reserved for issuance  under the
Company's 1996 Director Option Plan (the "Director  Plan"),  of which options to
purchase  15,000  shares have been  granted,  and  warrants to purchase  468,750
shares of Common Stock,  neither the Company nor any subsidiary has  outstanding
any options to purchase,  or any preemptive  rights or other rights to subscribe
for or to purchase,  any  securities  or  obligations  convertible  into, or any
contracts or  commitments  to issue or sell,  shares of its capital stock or any
such options, rights, convertible securities or obligations.  The Company is not
a party or subject to any  agreement or  understanding,  and, to the best of the
Company's knowledge,  there is no agreement or understanding between any persons
and/or  entities,  which  affects  or relates to the voting or giving of written
consents with respect to any security or by a director of the Company.

                         (iv) The issued and outstanding  shares of Common Stock
have been duly authorized and validly issued,  are fully paid and nonassessable,
have been issued in compliance  with all federal and state  securities  laws and
were not issued in  violation  of or subject to any  preemptive  rights or other
rights to  subscribe  for or  purchase  securities.  All issued and  outstanding
shares  of  capital  stock of each  subsidiary  of the  Company  have  been duly
authorized and validly issued and are fully paid and nonassessable.

                  2.4  Subsidiaries.   Other  than  Interlink  France  S.A.R.I.,
Interlink   Deutschland  GmbH,   Interlink   Iberica  S.A.  (Spain),   Interlink
(Switzerland) S.A., Interlink Computer Sciences,  Ltd. (United Kingdom), New Era
Systems Services, Ltd. (Canada), Era Nua Teoranta, Ltd. (Ireland), and Interlink
Computer  Sciences  (Barbados)  Inc.,  the  Company  does not  presently  own or
control,  directly  or  indirectly,  any  interest  in  any  other  corporation,
association,  or  other  business  entity.  Other  than  as  disclosed  in  each
statement,  annual,  quarterly and other  report,  registration  statement  (the
"Company SEC Documents") filed (other than preliminary  material) by the Company
with the U.S. Securities and Exchange Commission (the "SEC"), the Company is not
a participant in any joint venture, partnership or similar arrangement.

                                       3.
<PAGE>
                  2.5 Valid  Issuance of Common  Stock.  The Common  Stock to be
sold by the Company has been duly  authorized  and,  when issued,  delivered and
paid for in the manner  set forth in this  Agreement,  will be duly  authorized,
validly issued,  fully paid and nonassessable,  and will be free of restrictions
on transfer other than  restrictions  on transfer under this Agreement and under
applicable  state and federal  securities  laws. No  preemptive  rights or other
rights to subscribe for or purchase  exist with respect to the issuance and sale
of the Common Stock by the Company pursuant to this Agreement.

                  2.6  Governmental  Consents.  Other than  compliance  with the
Securities  Act of 1933,  as  amended  (the  "Act")  and such  filings as may be
required to be made with the National  Association  of  Securities  Dealers (the
"NASD"),  no consent,  approval,  order or  authorization  of, or  registration,
qualification,  designation,  declaration or filing with, any federal,  state or
local  governmental  authority  on  the  part  of the  Company  is  required  in
connection  with  the  consummation  of the  transactions  contemplated  by this
Agreement.

                  2.7  Offering.  Subject in part to the truth and  accuracy  of
Investor's  representations set forth in Section 3 of this Agreement, the offer,
sale and  issuance of the Common Stock as  contemplated  by this  Agreement  are
exempt from the  registration  requirements  of the Act, and neither the Company
nor any  authorized  agent  acting on its behalf will take any action  hereafter
that would cause the loss of such exemption.

                  2.8  Litigation.  Other than as  disclosed  in the Company SEC
Documents,  there are no legal or  governmental  actions,  suits or  proceedings
pending or, to the Company's  knowledge,  threatened to which the Company or any
of its subsidiaries is or may be a party or of which property owned or leased by
the Company or any of its  subsidiaries is or may be the subject,  or related to
environmental or  discrimination  matters,  which actions,  suits or proceedings
might,  individually  or in the  aggregate,  prevent  or  adversely  affect  the
transactions  contemplated  by this  Agreement  or result in a material  adverse
change in the  condition  (financial  or  otherwise),  properties,  business  or
results of operations of the Company and its subsidiaries  taken as a whole; and
no labor  disturbance by the employees of the Company or any of its subsidiaries
exists or, to the Company's  knowledge,  is imminent  which might be expected to
have a  material  adverse  effect on such  condition,  properties,  business  or
results of  operations.  Neither the Company  nor any of its  subsidiaries  is a
party or subject to the provisions of any material injunction,  judgment, decree
or  order  of  any  court,  regulatory  body,  administrative  agency  or  other
governmental body. There are no material legal or governmental actions, suits or
proceedings  pending  or, to the  Company's  knowledge,  threatened  against any
executive officers or directors of the Company.

                  2.9  Intellectual  Property.  Other than as  disclosed  in the
Company SEC  Documents,  the Company has  sufficient  title and ownership of all
patents,  trademarks,  service marks,  trade names,  copyrights,  trade secrets,
information,  proprietary rights and processes necessary for its business as now
conducted without any conflict with or

                                       4.
<PAGE>

infringement of the rights of others. Other than as disclosed in the Company SEC
Documents, there are no outstanding options, licenses, or agreements of any kind
relating  to the  foregoing,  nor is the  Company  bound  by or a  party  to any
options,  licenses  or  agreements  of any kind  with  respect  to the  patents,
trademarks,  service marks, trade names,  copyrights,  trade secrets,  licenses,
information, proprietary rights and processes of any other person or entity. The
Company  has not  received  any  communications  alleging  that the  Company has
violated or, by  conducting  its business as proposed,  would violate any of the
patents, trademarks,  service marks, trade names, copyrights or trade secrets or
other proprietary rights of any other person or entity. The Company is not aware
that any of its employees is obligated under any contract  (including  licenses,
covenants or  commitments of any nature) or other  agreement,  or subject to any
judgment,  decree or order of any court or  administrative  agency,  that  would
interfere  with the use of his or her best  efforts to promote the  interests of
the Company or that would conflict with the Company's business as proposed to be
conducted.  Neither  the  execution  nor  delivery  of this  Agreement,  nor the
carrying on of the Company's  business by the employees of the Company,  nor the
conduct  of the  Company's  business  as  proposed,  will,  to the  best  of the
Company's  knowledge,  conflict  with  or  result  in a  breach  of  the  terms,
conditions  or  provisions  of, or  constitute a default  under,  any  contract,
covenant or instrument  under which any of such employees is now obligated.  The
Company does not believe it is or will be necessary to utilize any inventions of
any of its  employees  (or  people it  currently  intends to hire) made prior to
their employment by the Company.

                  2.10  Conflicts.  Neither the  execution  nor delivery of this
Agreement,  nor the carrying on of the Company's  business  will, to the best of
the Company's  knowledge,  conflict  with or result in a material  breach of the
terms,  conditions or provisions of, or constitute a material default under, any
contract, covenant or instrument under which the Company or any of its employees
is now obligated.

                  2.11 Compliance with Other Instruments.  Except as to defaults
which  individually or in the aggregate would not be material to the Company and
its  subsidiaries  taken  as a  whole,  neither  the  Company  nor  any  of  its
subsidiaries  is in violation or default of any provision of its  certificate of
incorporation or bylaws, or other organizational  documents,  or is in breach of
or default with respect to any  provision of any  agreement,  judgment,  decree,
order, mortgage, deed of trust, lease, franchise,  license, indenture, permit or
other  instrument to which it is a party or by which it or any of its properties
are bound;  and,  except as to defaults which  individually  or in the aggregate
would not be material to the Company and its  subsidiaries  taken as a whole, to
the  Company's  knowledge,  there  does not  exist  any  state  of  facts  which
constitutes  an  event  of  default  on the  part  of the  Company  or any  such
subsidiary as defined in such  documents or which,  with notice or lapse of time
or both, would constitute such an event of default. The execution,  delivery and
performance  of  this  Agreement,  and  the  consummation  of  the  transactions
contemplated hereby and thereby,  will not result in any such violation or be in
conflict with or constitute, with or without the passage of time

                                       5.
<PAGE>


and giving of notice,  either a default  under any such  provision,  instrument,
judgment,  order,  writ,  decree or  contract  or an event  that  results in the
creation of any lien,  charge or  encumbrance  upon any assets of the Company or
the  suspension,  revocation,  impairment,  forfeiture,  or  nonrenewal  of  any
material permit, license,  authorization, or approval applicable to the Company,
its business or operations or any of its assets or properties.

                  2.12 Disclosure.  The Company has fully provided Investor with
all the  information  that such Investor has  requested for deciding  whether to
purchase the Common Stock.  Neither this Agreement,  nor any other statements or
certificates made or delivered in connection  herewith or therewith contains any
untrue  statement of a material fact or omits to state a material fact necessary
to make the statements herein or therein not misleading.

                  2.13 Registration  Rights.  Except for the registration rights
granted  under this  Agreement,  and as disclosed in the Company SEC  Documents,
there  are  no  other  stockholders  of  the  Company  that  have  been  granted
registration rights,  including piggyback rights, and the Company has not agreed
to grant any registration rights, to any person or entity.

                  2.14  Title  to  Property  and  Assets.  The  Company  or  the
applicable  subsidiary has good and  marketable  title to all the properties and
assets subject to no lien, mortgage,  pledge,  charge or encumbrance of any kind
except those which do not adversely  affect the use made and proposed to be made
of such  property  by the  Company  and its  subsidiaries.  The  Company  or the
applicable  subsidiary  holds its  leased  properties  under  valid and  binding
leases,  with such  exceptions as are not materially  significant in relation to
the business of the Company.  The Company owns or leases all such  properties as
are necessary to its operations as now conducted.

                  2.15  Financial  Statements.  The  Company  has  delivered  to
Investor its audited  financial  statements  (balance  sheet and profit and loss
statement,  statement  of  stockholders'  equity and  statement  of cash  flows,
including  notes  thereto)  at June 30, 1996 and for the fiscal year then ended,
and its  unaudited  financial  statements  (balance  sheet and  profit  and loss
statement)  as at and for the  3-month  period  ended  September  30,  1996 (the
audited and unaudited  financial  statements  are  collectively,  the "Financial
Statements").  The  Financial  Statements  of the Company and its  subsidiaries,
present fairly the financial  position of the Company and its  subsidiaries,  as
the case may be, as of the  respective  dates of such  financial  statements and
schedules,  and the results of operations  and changes in financial  position of
the Company and its subsidiaries, as the case may be, for the respective periods
covered  thereby.  Such Financial  Statements,  schedules and related notes have
been prepared in accordance  with United States  generally  accepted  accounting
principles applied on a consistent basis.

                  2.16     Changes.  Since September 30, 1996:

                                       6.
<PAGE>

                  (a) the Company and its  subsidiaries  have not  incurred  any
material liabilities or obligations,  indirect, direct or contingent, or entered
into any material verbal or written  agreement or other transaction which is not
in the ordinary course of business;

                  (b) the Company and its  subsidiaries  have not  sustained any
material loss or  interference  with their  respective  businesses or properties
from fire, flood, windstorm,  accident or other calamity, whether or not covered
by insurance;

                  (c) the  Company  has not paid or declared  any  dividends  or
other  distributions  with respect to its capital  stock and the Company and its
subsidiaries  are not in default in the payment of  principal or interest on any
outstanding debt obligations;

                  (d) There has not been any  change  in the  capital  stock or,
other than in the  ordinary  course of  business,  indebtedness  material to the
Company and its subsidiaries; and

                  (e)  there  has not been any  material  adverse  change or any
development  involving  or  which  may  reasonably  be  expected  to  involve  a
prospective  material adverse change, in the condition (financial or otherwise),
business,  properties, results of operations or prospects of the Company and its
subsidiaries taken as a whole.


                  2.17 SEC Documents;  Material Contracts. The Company has filed
each statement,  annual, quarterly and other report,  registration statement and
definitive  proxy  statement  required  to  be  filed  (other  than  preliminary
material) by the Company with the SEC subsequent to August 15, 1996. As of their
respective  filing  dates,  the Company SEC  Documents  complied in all material
respects with the requirements of the Act or the Securities Exchange Act of 1934
(the "1934  Act"),  as the case may be, and none of the  Company  SEC  Documents
contained any untrue statement of a material fact or omitted to state a material
fact  required to be stated  therein or  necessary to make the  statements  made
therein,  in light of the circumstances in which they were made, not misleading,
except to the extent corrected by any subsequently  filed Company SEC Documents.
The  Company's  Registration  Statement on Form S-1,  which became  effective on
August 14, 1996 (the "Registration  Statement"),  and the Company SEC Documents,
include certain  contracts as required by the SEC's rules and  regulations.  The
contracts  so  described in the  Registration  Statement  and in the Company SEC
Documents,  that are currently material to the Company and its business,  are in
full force and effect on the date  hereof.  Neither  the  Company nor any of its
subsidiaries, nor to the Company's knowledge, any other party is in breach of or
default under any of such contracts, except as to breaches or defaults which, in
any single case or in the aggregate would not have a material  adverse effect on
the Company or the subsidiary.


                                       7.
<PAGE>

                  2.18  Compliance  with  All  Laws.  The  Company  has not been
advised, and has no reason to believe, that either it or any of its subsidiaries
is not conducting  business in compliance  with all applicable  laws,  rules and
regulations of the jurisdictions in which it is conducting business,  including,
without limitation,  all applicable local, state and federal  environmental laws
and  regulations,  except  where  failure  to  be  so in  compliance  would  not
materially  adversely affect the condition  (financial or otherwise),  business,
results of operations or prospects of the Company and its subsidiaries  taken as
a whole.

                  2.19  Investment  Company.  The Company is not an  "investment
company" within the meaning of the Investment Company Act of 1940, as amended.

                  3. Representations and Warranties of Investor. Investor hereby
represents and warrants that:

                  3.1  Authorization.  Investor has full power and  authority to
execute and deliver,  and to consummate  the  transactions  contemplated  by the
Closing and this Agreement.  All corporate  action on the part of Investor,  its
officers,  directors  and  shareholders  necessary  for  (i) the  execution  and
delivery of, and the  consummation  of the  transactions  contemplated  by, this
Agreement,  and (ii) as of the Closing,  the  performance of all  obligations of
Investor under this Agreement,  has been taken.  This Agreement,  upon execution
and delivery by Investor and assuming the due and proper  execution and delivery
by the Company,  constitutes a legal,  valid and binding obligation of Investor,
enforceable  in  accordance  with its  terms,  except as may be  limited  by (i)
applicable  bankruptcy,  insolvency,  reorganization  or other  laws of  general
application  relating  to or  affecting  the  enforcement  of  creditors  rights
generally,  and (ii) the effect of rules of law  governing the  availability  of
equitable remedies.

                  3.2 Purchase Entirely for Own Account.  This Agreement is made
with Investor in reliance upon Investor's  representation to the Company,  which
by Investor's  execution of this Agreement  Investor hereby  confirms,  that the
Common Stock to be received by Investor (collectively, the "Securities") will be
acquired for investment  for Investor's own account,  not as a nominee or agent,
and not with a view to the resale or distribution of any part thereof,  and that
Investor has no present intention of selling,  granting any participation in, or
otherwise  distributing the same. By executing this Agreement,  Investor further
represents that Investor does not have any contract,  undertaking,  agreement or
arrangement with any person to sell,  transfer or grant  participations  to such
person or to any third person, with respect to any of the Securities.

                  3.3 Governmental Consents.  Other than compliance with the Act
and such  filings  as may be  required  to be made  with the NASD,  no  consent,
approval,   order  or   authorization   of,  or   registration,   qualification,
designation,   declaration  or  filing  with,   any  federal,   state  or  local
governmental  authority on the part of Investor is required in  connection  with
the consummation of the transactions contemplated by this Agreement.

                                       8.
<PAGE>

                  3.4 No Consent. No consent,  approval,  waiver or other action
by  any  entity  under  any  material  contract,  agreement,  indenture,  lease,
instrument  or other  document  to which  Investor  is a party or by which it is
bound is required or necessary for the execution,  delivery and  performance of,
or the  consummation  of the  transactions  contemplated  by, this  Agreement by
Investor.

                  3.5  Disclosure  of  Information.  Investor  believes  it  has
received all the information it considers  necessary or appropriate for deciding
whether to purchase the Common Stock.  Investor  further  represents that it has
had an  opportunity  to ask  questions  and  receive  answers  from the  Company
regarding  the terms and  conditions of the offering of the Common Stock and the
business,  properties,  prospects  and financial  condition of the Company.  The
foregoing,  however, does not limit or modify the representations and warranties
of the Company in Section 2 of this  Agreement  or the right of Investor to rely
thereon.

                  3.6  Investment   Experience.   Investor  is  an  investor  in
securities of companies in the  development  stage and  acknowledges  that it is
able to fend for itself,  can bear the economic risk of its investment,  and has
such  knowledge  and  experience  in  financial  or business  matters that it is
capable  of  evaluating  the merits  and risks of the  investment  in the Common
Stock.  Investor has not been  organized for the purpose of acquiring the Common
Stock.

                  3.7 Accredited Investor.  Investor is an "accredited investor"
within the meaning of SEC Rule 501 of Regulation D, as presently in effect.

                  3.8  Restricted  Securities.  Investor  understands  that  the
Securities it is purchasing are  characterized as "restricted  securities" under
the federal securities laws inasmuch as they are being acquired from the Company
in a transaction  not  involving a public  offering and that under such laws and
applicable  regulations such securities may be resold without registration under
the Act, only in certain limited  circumstances.  In this  connection,  Investor
represents  that it is familiar  with SEC Rule 144, as presently in effect,  and
understands the resale limitations imposed thereby and by the Act.

                  3.9 Further  Limitations  on  Disposition.  Without in any way
limiting the  representations  set forth above,  Investor  further agrees not to
make any  disposition of all or any portion of the  Securities  unless and until
the  transferee has agreed in writing for the benefit of the Company to be bound
by this Section 3 provided and to the extent this Section is applicable, and:

                  (a) There is then in effect a Registration Statement under the
Act  covering  such  proposed  disposition  and  such  disposition  is  made  in
accordance with such Registration Statement; or


                                       9.
<PAGE>

                  (b) If  reasonably  requested by the Company,  Investor  shall
have furnished the Company with an opinion of counsel,  reasonably  satisfactory
to the  Company  that such  disposition  will not require  registration  of such
shares under the Act. It is agreed that the Company will not require opinions of
counsel  for   transactions   made  pursuant  to  Rule  144  except  in  unusual
circumstances.

                  3.10 Legends.  Each  certificate  or  instrument  representing
Shares shall bear legends in substantially the following forms:

                         (i) "THE  SECURITIES  REPRESENTED  BY THIS  CERTIFICATE
         HAVE  NOT  BEEN  REGISTERED  UNDER  THE  SECURITIES  ACT OF  1933  (THE
         'SECURITIES  ACT') AND ARE  'RESTRICTED  SECURITIES' AS DEFINED IN RULE
         144  PROMULGATED  UNDER THE  SECURITIES  ACT. THE SECURITIES MAY NOT BE
         SOLD  OR  OFFERED  FOR  SALE OR  OTHERWISE  DISTRIBUTED  EXCEPT  (I) IN
         CONJUNCTION WITH AN EFFECTIVE REGISTRATION STATEMENT FOR THE SECURITIES
         UNDER THE SECURITIES ACT, OR (II) IN COMPLIANCE WITH RULE 144, OR (III)
         PURSUANT TO AN OPINION OF COUNSEL  SATISFACTORY  TO THE ISSUER OF THESE
         SECURITIES  THAT SUCH  REGISTRATION OR COMPLIANCE IS NOT REQUIRED AS TO
         SUCH SALE, OFFER OR DISTRIBUTION."

                        (ii) Any other  legends  required by  California  law or
         other applicable blue sky or state securities laws.

The Company  need not register a transfer of any Shares,  and may also  instruct
its  transfer  agent not to  register  a  transfer  of any  Shares,  unless  the
conditions  specified  in the  foregoing  legends  are  satisfied  to the extent
applicable.

                  4. Right to Notification.

                  4.1  Notification  of Acquisition  of Securities.  The Company
will notify Investor in the event any person or entity acquires securities which
results  in such  person  or entity  owning  five  (5%)  percent  or more of the
securities of the Company or a Spinoff  (defined as a subsidiary of the Company,
to  which  the  Company  transfers  substantially  all of  its  assets  used  in
development  and/or  production  of TCP/IP  products)  promptly when the Company
becomes aware of the  acquisition.  In the event any person or entity varies its
ownership  above five (5%) percent by one (1%) percent or more, then the Company
shall  notify  Investor  immediately  after the  Company  receives a copy of the
applicable  Form 13 or any  other  applicable  form or  earlier  if the  Company
becomes aware of such  acquisition  prior to receiving the applicable form filed
with the SEC.


                                       10.
<PAGE>

                  4.2  Notification  of  Receipt  of  Acquisition   Proposal  or
Initiation  of Sale.  In the event that the Board of Directors of the Company or
the  Spinoff  (i)  receives  an offer to be  acquired  by means of (x) a merger,
consolidation or other business  combination  pursuant to which the stockholders
of the  Company or a Spinoff  immediately  prior to the  effective  date of such
transaction  have  beneficial  ownership of less than fifty percent (50%) of the
total  combined  voting  power  for  election  of  directors  of  the  surviving
corporation  immediately  following such transaction;  or (y) the sale of all or
substantially  all of the assets of the  Company or a Spinoff,  or (ii) votes to
initiate a sale to any other person or entity of (xx) twenty-five  (25%) percent
or more of the Actual  Voting  Power of the  Company  (as defined in Section 4.3
below) or a Spinoff,  or (yy) all or  substantially  all of the  Company's  or a
Spinoff's  assets,  prior to accepting such  acquisition  proposal or initiating
such sale,  the Company or the Spinoff shall provide to Investor  written notice
(the "Notice") of the proposed terms of such acquisition proposal or sale within
two (2) business days of receipt of such acquisition  proposal or the initiation
of a sale of the Company or the Spinoff.  The Notice shall include the following
information:  (a) the identity of the party making the acquisition  proposal and
(b) the specific terms of the  acquisition  proposal or the initiation of a sale
of the Company or the Spinoff.  Further,  the Company  shall  provide a true and
complete copy of the acquisition  proposal if in writing,  or a complete written
summary  thereof if the  proposal is not in writing,  and any and all  documents
containing  or referring to  non-public  information  of the Company that are or
have been  supplied to the party making the  acquisition  proposal.  The Company
agrees not to accept an  acquisition  proposal or vote to initiate a sale of the
Company or the Spinoff as provided  for in this  Section 4.2 earlier than twenty
(20) days from the date of Investor's receipt of the Notice.

                  4.3 Actual Voting Power.  "Actual  Voting Power of the Company
or a  Spinoff"  shall  mean the total  number  of votes  that may be cast in the
election of Directors of the Company or a Spinoff at any meeting of stockholders
of the Company or a Spinoff if all shares of Common  Stock and other  securities
of the  Company or a Spinoff  entitled  to vote  generally  in the  election  of
Directors of the Company or a Spinoff  were  present and voted at such  meeting,
other than  votes  that may be cast only by one class or series of stock  (other
than shares of Common Stock) or upon the happening of a contingency.

                  4.4 Term.  The Notice  requirements  set forth in Section  4.1
shall commence on December 10, 1996 and shall terminate on December 31, 1999.


                                       11.
<PAGE>


                  5. Registration Rights.

                  5.1 Request for Registration.

                  (a) If the Company  shall receive at any time after August 15,
1997, a written  request  from  Investor  that the Company  file a  registration
statement under the Act covering the  registration of the Common Stock purchased
hereunder,  then the Company  shall  effect as soon as  practicable,  and in any
event within 60 days of the receipt of such request,  the registration under the
Act of all securities which Investor requests to be registered.

                  (b) If Investor  intends to distribute the securities  covered
by its request by means of an underwriting, Investor shall so advise the Company
as a part of its request made pursuant to subsection (a) above.  The underwriter
will be selected by the Company and shall be reasonably  acceptable to Investor.
Investor shall (together with the Company) enter into an underwriting  agreement
in  customary  form  with the  underwriter  or  underwriters  selected  for such
underwriting.

                  (c)  Notwithstanding  the  foregoing,  if  the  Company  shall
furnish to Investor a certificate  signed by the Chief Executive  Officer of the
Company stating that in the good faith judgment of the Board of Directors of the
Company,  it would be seriously  detrimental to the Company and its stockholders
for such  registration  statement to be filed and it is  therefore  essential to
defer the filing of such  registration  statement,  the  Company  shall have the
right to defer  taking  action  with  respect to such filing for a period of not
more than 120 days after receipt of the request of Investor;  provided, however,
that the Company may not utilize  this right more than once in any  twelve-month
period.

                  (d) In addition, the Company shall not be obligated to effect,
or to take any action to effect, any registration pursuant to this Section 5.1:

                                (i)  After  the   Company   has   effected   one
registration,  other than a  registration  which is made on Form S-3 pursuant to
this Section 5.1, and such registration has been declared or ordered effective;

                                (ii) If all securities  which Investor  requests
to be  registered  may  immediately  be sold  under  Rule 144  during any 90-day
period.

                                (iii) More than once in any 12-month period.

                  5.2 Obligations of the Company.  Whenever  required under this
Section 5 to effect the  registration of any  securities,  the Company shall, as
expeditiously as reasonably possible:


                                       12.
<PAGE>

                  (a)  Prepare  and file with the SEC a  registration  statement
with respect to such securities and use commercially reasonable efforts to cause
such  registration  statement  to become  effective,  and,  upon the  request of
Investor,  keep such registration  statement effective for a period of up to one
hundred  twenty  (120)  days  or  until  the  distribution  contemplated  in the
Registration Statement has been completed;  provided, however, that such 120-day
period  shall be  extended  for a period of time  equal to the  period  Investor
refrains  from  selling  any  securities  included in such  registration  at the
request of an underwriter of Common Stock (or other securities) of the Company.

                  (b)  Prepare  and  file  with  the  SEC  such  amendments  and
supplements to such registration statement and the prospectus used in connection
with  such  registration  statement  as may be  necessary  to  comply  with  the
provisions of the Act with respect to the disposition of all securities  covered
by such registration statement.

                  (c)  Furnish  to  Investor   such   numbers  of  copies  of  a
prospectus,   including  a  preliminary  prospectus,   in  conformity  with  the
requirements of the Act, and such other documents as they may reasonably request
in order to facilitate the disposition of securities.

                  (d)  Use  commercially  reasonable  efforts  to  register  and
qualify the securities  covered by such registration  statement under such other
securities  or Blue  Sky  laws of such  jurisdictions  as  shall  be  reasonably
requested  by  Investor;  provided  that the  Company  shall not be  required in
connection  therewith or as a condition  thereto to qualify to do business or to
file  a  general   consent  to  service  of  process  in  any  such   states  or
jurisdictions,  unless  the  Company  is  already  subject  to  service  in such
jurisdiction and except as may be required by the Act.

                  (e) In the event of any underwritten  public  offering,  enter
into and perform its obligations under an underwriting  agreement,  in usual and
customary form, with the managing underwriter of such offering,  said form to be
agreeable  to the Company and its  counsel.  Investor  shall also enter into and
perform its obligations under such an agreement.

                  (f) Notify Investor at any time when a prospectus  relating to
such  registration  statement is required to be  delivered  under the Act of the
happening  of any  event as a result of which the  prospectus  included  in such
registration  statement,  as then in effect,  includes an untrue  statement of a
material fact or omits to state a material fact required to be stated therein or
necessary  to make the  statements  therein not  misleading  in the light of the
circumstances then existing.

                  (g) Cause all such securities registered pursuant hereunder to
be listed on each securities  exchange on which similar securities issued by the
Company are then listed.


                                       13.
<PAGE>

                  (h) Use  commercially  reasonable  efforts to furnish,  at the
request  of  Investor,  on  the  date  that  securities  are  delivered  to  the
underwriters for sale in connection with a registration pursuant to this Section
5,  if  such  securities  are  being  sold  through  underwriters,  or,  if such
securities  are not  being  sold  through  underwriters,  on the  date  that the
registration statement with respect to such securities becomes effective, (i) an
opinion,  dated such date,  of the  counsel  representing  the  Company  for the
purposes of such registration,  in form and substance as is customarily given to
underwriters in an underwritten public offering,  addressed to the underwriters,
if any, and to Investor and (ii) a letter dated such date,  from the independent
certified  public  accountants  of the  Company,  in form  and  substance  as is
customarily given by independent certified public accountants to underwriters in
an underwritten public offering,  addressed to the underwriters,  if any, and to
Investor.

                  5.3  Expenses  of   Registration.   All  expenses  other  than
underwriting  discounts and commissions  incurred in connection with the request
for registration  pursuant to Section 5.1,  including  (without  limitation) all
registration, filing and qualification fees, printers' and accounting fees, fees
and  disbursements of counsel for the Company  (including fees and disbursements
of counsel for the Company in its capacity as counsel to Investor hereunder;  if
Company  counsel does not make itself  available for this  purpose,  the Company
will pay the  reasonable  fees and  disbursements  of one counsel for  Investor)
shall be borne by the Company and all such expenses for subsequent registrations
shall be borne by Investor;  provided,  however,  that the Company  shall not be
required to pay for any expenses of any  registration  proceeding begun pursuant
to Section 5.1 if the  registration  request is  subsequently  withdrawn  at the
request of Investor (in which case Investor shall bear such  expense);  provided
further,  however, that if at the time of such withdrawal,  Investor has learned
of a material  adverse  change in the condition,  business,  or prospects of the
Company from that known to Investor at the time of its request and has withdrawn
the request with reasonable  promptness  following  disclosure by the Company of
such material adverse change,  then Investor shall not be required to pay any of
such expenses and shall retain its rights pursuant to Section 5.1.

                  5.4 Indemnification.  In the event any securities are included
in a registration statement under this Section 5:

                  (a) To the extent permitted by law, the Company will indemnify
and hold harmless Investor, any underwriter (as defined in the Act) for Investor
and each person, if any, who controls Investor or underwriter within the meaning
of the Act or the 1934 Act, against any losses, claims,  damages, or liabilities
(joint or  several) to which they may become  subject  under the Act or the 1934
Act or other federal or state law, insofar as such losses,  claims,  damages, or
liabilities  (or actions in respect  thereof) arise out of or are based upon any
of  the  following   statements,   omissions  or  violations   (collectively   a
"Violation"): (i) any untrue statement or alleged untrue statement of a material
fact contained in such registration statement, including any preliminary

                                       14.
<PAGE>

prospectus  or  final  prospectus   contained   therein  or  any  amendments  or
supplements  thereto,  (ii) the omission or alleged  omission to state therein a
material fact required to be stated therein, or necessary to make the statements
therein not  misleading,  or (iii) any  violation  or alleged  violation  by the
Company  of the Act,  the 1934  Act,  any  state  securities  law or any rule or
regulation  promulgated  under the Act, or the 1934 Act or any state  securities
law;  and the Company  will pay to each  Investor,  underwriter  or  controlling
person, as incurred,  any legal or other expenses reasonably incurred by them in
connection  with  investigating  or  defending  any such  loss,  claim,  damage,
liability, or action; provided,  however, that the indemnity agreement contained
in this  subsection  5.4(a) shall not apply to amounts paid in settlement of any
such loss, claim,  damage,  liability,  or action if such settlement is effected
without the  consent of the Company  (which  consent  shall not be  unreasonably
withheld),  nor shall the  Company be liable in any such case for any such loss,
claim,  damage,  liability,  or action to the extent that it arises out of or is
based upon a Violation  which  occurs in reliance  upon and in  conformity  with
written  information  furnished  expressly  for  use  in  connection  with  such
registration by any Investor, underwriter or controlling person.

                  (b) To the extent  permitted by law,  Investor will  indemnify
and hold harmless the Company,  each of its directors,  each of its officers who
has signed the  registration  statement,  each person,  if any, who controls the
Company  within the meaning of the Act,  any  underwriter,  and any  controlling
person of any such underwriter or Investor, against any losses, claims, damages,
or  liabilities  (joint or  several) to which any of the  foregoing  persons may
become  subject,  under the Act, or the 1934 Act or other  federal or state law,
insofar as such losses,  claims,  damages, or liabilities (or actions in respect
thereto)  arise  out of or are  based  upon any  Violation,  in each case to the
extent (and only to the extent) that such Violation  occurs in reliance upon and
in conformity with written  information  furnished by Investor expressly for use
in connection with such  registration;  and Investor will pay, as incurred,  any
legal or  other  expenses  reasonably  incurred  by any  person  intended  to be
indemnified pursuant to this subsection 5.4(b), in connection with investigating
or defending  any such loss,  claim,  damage,  liability,  or action;  provided,
however,  that the indemnity agreement contained in this subsection 5.4(b) shall
not  apply to  amounts  paid in  settlement  of any such  loss,  claim,  damage,
liability  or action if such  settlement  is  effected  without  the  consent of
Investor,  which consent shall not be unreasonably withheld;  provided, that, in
no event  shall any  indemnity  under this  subsection  5.4(b)  exceed the gross
proceeds from the offering received by Investor.

                  (c) Promptly after receipt by an indemnified  party under this
Section  5.4  of  notice  of  the  commencement  of any  action  (including  any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying  party under this Section 5.4, deliver to
the  indemnifying  party a written  notice of the  commencement  thereof and the
indemnifying  party shall have the right to  participate  in, and, to the extent
the indemnifying  party so desires,  jointly with any other  indemnifying  party
similarly noticed, to assume the defense thereof with counsel mutually

                                       15.
<PAGE>

satisfactory  to the  parties;  provided,  however,  that an  indemnified  party
(together with all other  indemnified  parties which may be represented  without
conflict by one counsel)  shall have the right to retain one  separate  counsel,
with  the  fees  and  expenses  to  be  paid  by  the  indemnifying   party,  if
representation  of  such  indemnified  party  by  the  counsel  retained  by the
indemnifying  party would be inappropriate due to actual or potential  differing
interests between such indemnified party and any other party represented by such
counsel  in such  proceeding.  The  failure  to  deliver  written  notice to the
indemnifying  party within a  reasonable  time of the  commencement  of any such
action, if prejudicial to its ability to defend such action,  shall relieve such
indemnifying  party of any liability to the indemnified party under this Section
5.4, but the omission so to deliver  written  notice to the  indemnifying  party
will not relieve it of any liability that it may have to any  indemnified  party
otherwise than under this Section 5.4.

                  (d) If the indemnification provided for in this Section 5.4 is
held by a court of competent  jurisdiction  to be  unavailable to an indemnified
party with respect to any loss, liability, claim, damage, or expense referred to
therein,  then the indemnifying  party, in lieu of indemnifying such indemnified
party  hereunder,  shall  contribute  to the  amount  paid  or  payable  by such
indemnified party as a result of such loss, liability, claim, damage, or expense
in such  proportion  as is  appropriate  to reflect  the  relative  fault of the
indemnifying  party on the one hand and of the indemnified party on the other in
connection  with  the  statements  or  omissions  that  resulted  in such  loss,
liability,  claim,  damage,  or expense as well as any other relevant  equitable
considerations.  The  relative  fault  of  the  indemnifying  party  and  of the
indemnified  party shall be  determined  by reference  to,  among other  things,
whether  the  untrue or  alleged  untrue  statement  of a  material  fact or the
omission  to state a  material  fact  relates  to  information  supplied  by the
indemnifying party or by the indemnified party and the parties' relative intent,
knowledge,  access to  information,  and  opportunity to correct or prevent such
statement or omission.

                  (e)  Notwithstanding  the  foregoing,  to the extent  that the
provisions on  indemnification  and  contribution  contained in the underwriting
agreement  entered into in connection with the underwritten  public offering are
in conflict with the foregoing  provisions,  the provisions in the  underwriting
agreement shall control.

                  (f) The  obligations  of the Company and  Investor  under this
Section 5.4 shall  survive the  completion  of any offering of  securities  in a
registration statement under this Section 5, and otherwise.

                  5.5 Limitations on Subsequent  Registration  Rights.  From and
after the date of this  Agreement,  the  Company  shall not,  without  the prior
written  consent  of  Investor,  enter  into any  agreement  with any  holder or
prospective  holder of any  securities  of the  Company  which  would allow such
holder or prospective  holder (a) to include such securities in any registration
filed under Section 5.1 hereof,  unless under the terms of such agreement,  such
holder or prospective holder may include such securities

                                       16.
<PAGE>

in any such registration only to the extent that the inclusion of its securities
will not reduce the amount of the  securities of Investor  which are included or
(b) to make a  demand  registration  which  could  result  in such  registration
statement  being declared  effective  prior to the earlier of August 15, 1997 or
within one hundred twenty (120) days of the effective  date of any  registration
effected pursuant to Section 5.1.

                  6. Right of First Offer.

                  6.1 New  Issuances.  The Company hereby grants to Investor the
right of first offer (the  "Right of First  Offer") to purchase a pro rata share
(rounded to the next lowest number) of all (or any part) of any "New Securities"
(as defined in Section 6.2) that the Company  may,  from time to time propose to
sell and issue in a private equity financing.  Such pro rata share, for purposes
of this right of first offer, is the ratio of the number of Shares then owned by
Investor to the total number of shares of Common Stock  outstanding  immediately
prior to such  issuance.  This  Right of First  Offer  shall be  subject  to the
following provisions:

                  6.2  "New  Securities"  shall  mean  any  Common  Stock of the
Company whether or not authorized on the date hereof,  and rights,  options,  or
warrants to purchase  Common Stock and equity  securities of any type whatsoever
that are, or may become, convertible into Common Stock; provided,  however, that
"New Securities" does not include the following:

                  (a)  issuances of any other  securities  issued upon any stock
split, stock dividend, recapitalization, merger, consolidation or similar event;

                  (b)  securities  of  the  Company   issued   pursuant  to  the
acquisition of a business by the Company by merger, purchase of assets, or other
acquisition or reorganization approved by the Board of Directors;

                  (c)  securities  of the  Company  issued  in  connection  with
equipment lease transactions, loan guarantees,  commercial loans, bank financing
transactions or technology licenses approved by the Board of Directors; and

                  (d) shares of Common  Stock,  warrants to  purchase  shares of
Common Stock or options to purchase shares of Common Stock, issued or granted to
officers,  directors,  employees or consultants of the Company pursuant to stock
plans and option plans or other compensatory  arrangements approved by the Board
of Directors.

                  6.3 Notice of New  Securities.  In the event that the  Company
proposes to  undertake  an issuance of New  Securities,  it shall give  Investor
written notice of its  intention,  describing  the type of New  Securities,  the
price,  and the general terms upon which the Company proposes to issue the same.
Investor shall have ten (10) business days after receipt of such notice to agree
to purchase its pro rata share of such New

                                       17.
<PAGE>

Securities  at the price and upon the terms  specified  in the  notice by giving
written notice to the Company and stating therein the quantity of New Securities
to be purchased.

                  6.4  Exercise  of Right  of First  Offer.  In the  event  that
Investor  fails to  exercise in full the right of first  refusal  within the ten
(10)  business day period  specified  above,  the Company shall have ninety (90)
days  thereafter to sell (or enter into an agreement to sell) the New Securities
respecting  which the right of Investor  was not  exercised  at a price and upon
terms  no  more  favorable  to the  purchasers  thereof  than  specified  in the
Company's  notice.  In the event the Company  has not sold (or  entered  into an
agreement to sell) the New Securities  within ninety (90) day period the Company
shall not thereafter  issue or sell any New  Securities,  without first offering
such New Securities to the Investor in the manner provided above.

                  6.5  Transferability.  This  Right of First  Offer  may not be
transferred or assigned by Investor.

                  6.6 Closing.  The purchase and sale of any securities pursuant
to the  exercise  of the Right of First  Offer shall take place at 10:00 a.m. on
the fifth business day following  expiration or early termination of all waiting
periods  imposed on such  purchase and sale by the  Hart-Scott-Rodino  Antitrust
Improvements Act of 1976 (the "HSR Act"), or, if no waiting period is imposed on
such  purchase and sale by the HSR Act,  not later than five (5)  business  days
following Investor's exercise of the Right of First Offer. Any such purchase and
sale shall occur at the offices of the Company  located at the address set forth
on the signature page hereof, or at such other time and place as the Company and
Investor  may  agree.  The  Company  and  Investor  will use their  commercially
reasonable efforts to comply with all Federal and state laws and regulations and
stock  exchange  listing  requirements  applicable  to any  purchase and sale of
securities pursuant to the exercise of the Right of First Offer. The issuance of
such shares shall be subject to compliance  with applicable laws and regulations
of any applicable stock exchange and there shall not then be in effect any order
enjoining or restraining such exercise or issuance.

                  6.7  Reservation  of Shares.  The Company agrees that it shall
not take any of the  actions or series of actions  referred  to in  Paragraph  6
above  which  would  have the  effect of  triggering  the right of  Investor  to
exercise  the Right of First  Offer  unless the  Company  shall have an adequate
number of shares  available or reserved to satisfy any obligation it may have to
issue shares under Paragraph 6 above.

                  6.8 Term.  The  right to  purchase  additional  shares in this
Section 6 shall terminate on December 31, 1999.

                  7.  Conditions  of  Investor's  Obligations  at  Closing.  The
obligations  of Investor  under  subsection 1.2 of this Agreement are subject to
the fulfillment on or

                                       18.
<PAGE>

before the  Closing  of each of the  following  conditions,  the waiver of which
shall not be effective without Investor's consent thereto:

                  7.1  Representations  and Warranties.  The representations and
warranties of the Company  contained in Section 2 shall be true on and as of the
Closing with the same effect as though such  representations  and warranties had
been made on and as of the date of such Closing.

                  7.2 Performance. The Company shall have performed and complied
with all agreements, obligations and conditions contained in this Agreement that
are required to be performed or complied with by it on or before the Closing.

                  7.3 Qualifications. All authorizations, approvals, or permits,
if any, of any governmental authority or regulatory body of the United States or
of any state that are required in connection  with the lawful  issuance and sale
of the  Securities  pursuant  to  this  Agreement  shall  be duly  obtained  and
effective as of the Closing.

                  7.4  Proceedings  and  Documents.   All  corporate  and  other
proceedings in connection with the transactions  contemplated at the Closing and
all documents  incident  thereto shall be  reasonably  satisfactory  in form and
substance to Investor,  and it shall have received all such counterpart original
and certified or other copies of such documents as it may reasonably request.

                  7.5 Opinion of Company  Counsel.  Investor shall have received
from Wilson,  Sonsini,  Goodrich & Rosati,  counsel for the Company, an opinion,
dated  as of the  Closing,  in a  form  reasonably  acceptable  to  counsel  for
Investor.

                  7.6 Waiver of Registration  Rights. The Company shall obtain a
waiver  and/or  consent  from the  requisite  number of holders  of  Registrable
Securities,  as defined in that certain  Registration  Rights  Agreement,  dated
January 27,  1994,  by and among the  Company and each of the parties  listed on
Exhibit A thereto (the  "Rights  Agreement"),  of any and all rights  granted by
that certain Rights Agreement, as required by the Rights Agreement.

                  8.  Conditions of the Company's  Obligations  at Closing.  The
obligations  of the Company to Investor  under this Agreement are subject to the
fulfillment  on or before the  Closing of each of the  following  conditions  by
Investor:

                  8.1  Representations  and Warranties.  The representations and
warranties  of  Investor  contained  in Section 3 shall be true on and as of the
Closing with the same effect as though such  representations  and warranties had
been made on and as of the Closing.

                  8.2  Payment  of  Purchase  Price.  The  Investor  shall  have
delivered the purchase price specified in Section 1.

                                       19.
<PAGE>

                  8.3 Qualifications. All authorizations, approvals, or permits,
if any, of any governmental authority or regulatory body of the United States or
of any state that are required in connection  with the lawful  issuance and sale
of the  Securities  pursuant  to  this  Agreement  shall  be duly  obtained  and
effective as of the Closing.

                  9. Investor  Notice.  In the event that Investor  (which,  for
purposes of this  Section 9 includes  Investor,  its  affiliates  and all of its
subsidiaries)  intends  to,  directly  or  indirectly,  acquire,  or enter  into
discussions,  negotiations,  arrangements or understandings with any third party
to  acquire  prior to the  expiration  of this  Section  9  (including,  without
limitation,  the lapse of the  negative  covenants  of this Section 9.1 upon the
occurrence  of any of the events  described  in  Section  9.1(a)  through  (c)),
beneficial  ownership of any Common Stock and any other securities issued by the
Company  having the  ordinary  power to vote in the election of directors of the
Company  (other than  securities  having such power only upon the happening of a
contingency)  ("Voting Stock"), any securities  convertible into or exchangeable
for Voting Stock,  or any other right to acquire  Voting Stock  (except,  in any
case,  by way of  stock  dividends  or other  distributions  or  offerings  made
available  to the holders of Voting Stock  generally)  and if the effect of such
acquisition would be to increase the voting power of all Voting Stock then owned
by Investor or which Investor has a right to acquire more than 9.9% of the total
voting power of all Voting Stock then outstanding, Investor shall provide to the
Company prior written notice of the proposed  acquisition of Voting Stock.  Such
notice shall include the specific terms of the proposed method of acquisition of
the  securities  of the  Company or the Spinoff  and shall be  delivered  to the
Company  four  business   days  prior  to  the  closing  of  such   transaction.
Notwithstanding  the foregoing,  Investor may acquire Voting Stock without first
providing the Company with prior written notice upon the following events:

                  (a) if any person or group not  affiliated  with  Investor and
then owning  Voting  Stock  representing  at least 5% of the voting power of all
Voting Stock then  outstanding  provides  written notice to the Company or files
any document with the SEC that contains terms that put the Company reasonably on
notice of the likelihood  that such person or group has acquired or is proposing
to acquire any shares of Voting  Stock or the right to acquire  shares of Voting
Stock having aggregate  voting power of more than  twenty-five  percent (25%) of
the total voting power of all shares of Voting  Stock then  outstanding  and, in
the case of a proposal to acquire  such  shares,  the  proposal  and any related
offers to purchase  shares are not  withdrawn  or  terminated  prior to Investor
making an offer to acquire  Voting Stock or  acquiring  Voting Stock in response
thereto;  provided,  however, that the negative covenants of this Section 9 will
resume following the withdrawal of any proposal or offer to purchase shares made
in accordance with this Section 9;

                  (b) if it is publicly  disclosed or Investor  otherwise learns
that the  Company  has  entered  into any letter of intent or  agreement  with a
person or group  that,  if  consummated,  would  result in such  person or group
owning or having the right to

                                       20.
<PAGE>

acquire shares of Voting Stock having aggregate voting power of more than 20% of
the total voting power of all shares of Voting Stock then outstanding;

                  (c) if a tender  offer is made as evidenced by the filing with
the SEC of a Schedule  14D-1 (or any successor  schedule or form  promulgated or
adopted  for such  purpose  by the SEC) and the actual  dissemination  of tender
offer  materials to security  holders by another  person or group to purchase or
exchange for cash or other  consideration any Voting Stock which, if successful,
would  result in such  person or group  owning  or having  the right to  acquire
shares of Voting Stock with aggregate  voting power of at least 50% of the total
voting power of the Company then in effect; or

                  (d) upon the  earlier of a merger,  consolidation,  or sale of
substantially all of the Company's assets or December 31, 1999.

                  (e) Excluded Shares. For purposes of this agreement,  Investor
will not be deemed to have  beneficial  ownership of any Voting Stock held by an
Investor  pension plan or other  employee  benefit  program if Investor does not
have the power to control the investment decisions of such plan or program.

                  10. Miscellaneous.

                  10.1 Survival of Warranties.  The warranties,  representations
and covenants of the Company and Investor  contained in or made pursuant to this
Agreement  shall survive the  execution  and delivery of this  Agreement and the
Closing  and shall in no way be  affected  by any  investigation  of the subject
matter thereof made by or on behalf of Investor or the Company.

                  10.2 Assignment;  Successors and Assigns. No provision of this
Agreement may be assigned  without the prior written  consent of the other party
hereto.  Except as otherwise  provided herein,  the terms and conditions of this
Agreement  shall  inure to the  benefit  of and be binding  upon the  respective
successors and assigns of the parties (including transferees of any Securities).
Nothing in this  Agreement,  express or implied,  is intended to confer upon any
party other than the parties hereto or their  respective  successors and assigns
any rights,  remedies,  obligations,  or liabilities  under or by reason of this
Agreement, except as expressly provided in this Agreement.

                  10.3 Governing  Law. This  Agreement  shall be governed by and
construed  under the laws of the State of  California  as applied to  agreements
among  California  residents  entered into and to be performed  entirely  within
California.

                  10.4  Counterparts.  This  Agreement may be executed in two or
more counterparts,  each of which shall be deemed an original,  but all of which
together shall constitute one and the same instrument.


                                       21.
<PAGE>

                  10.5 Titles and  Subtitles.  The titles and subtitles  used in
this  Agreement  are used for  convenience  only and are not to be considered in
construing or interpreting this Agreement.

                  10.6  Notices,  etc.  All  notices  and  other  communications
required  or  permitted  hereunder  shall  be in  writing  and  shall be sent by
personal  delivery,  facsimile,  overnight  courier  or mailed by  certified  or
registered mail,  postage prepaid,  return receipt  requested,  to the facsimile
number or address as follows:

                  Company: Interlink Computer Sciences, Inc.
                                    47370 Fremont Boulevard
                                    Fremont, California 94538
                                    Telephone:       (510) 657-9800
                                    Facsimile:       (510) 659-6381
                                    Attention:       Charles W. Jepson

                  with a copy (which will not constitute notice) to:

                                    Wilson, Sonsini, Goodrich & Rosati
                                    650 Page Mill Road
                                    Palo Alto, California 94304-1050
                                    Telephone:       (415) 493-9300
                                    Facsimile:       (415) 493-6811
                                    Attention:       Thomas C. DeFilipps, Esq.

                  Investor:         Cisco Systems, Inc.
                                    170 West Tasman Drive
                                    San Jose, California 95134-1706
                                    Telephone:       (408) 526-4000
                                    Facsimile:       (408) 526-7110
                                    Attention:       Dan Scheinman, Esq.

                  with a copy (which will not constitute notice) to:

                                    Brobeck, Phleger & Harrison, LLP
                                    2200 Geng Road
                                    Two Embarcadero Place
                                    Palo Alto, CA  94303
                                    Telephone:  (415) 424-0160
                                    Facsimile:  (415) 496-2885
                                    Attention:  Edward M. Leonard, Esq.

or to such other  facsimile  number or address  provided  to the parties to this
Agreement  in  accordance   with  this  Section  10.6.  Such  notices  or  other
communications  shall be deemed delivered upon receipt, in the case of overnight
delivery, personal delivery or

                                       22.
<PAGE>

facsimile  transmission  (as evidenced by the confirmation  thereof),  or 2 days
after deposit in the mails (as determined by reference to the postmark).

                  10.7 Finder's Fee.  Each party  represents  that it neither is
nor will be obligated for any finders' fee or commission in connection with this
transaction.  Investor agrees to indemnify and to hold harmless the Company from
any liability for any commission or compensation in the nature of a finders' fee
(and the costs and  expenses of  defending  against  such  liability or asserted
liability) for which such Investor or any of its officers, partners,  employees,
or representatives is responsible.

                  The Company  agrees to indemnify  and hold  harmless  Investor
from any  liability  for any  commission  or  compensation  in the  nature  of a
finders' fee (and the costs and expenses of defending  against such liability or
asserted  liability) for which the Company or any of its officers,  employees or
representatives is responsible.

                  10.8  Expenses.   Irrespective   of  whether  the  Closing  is
effected,  each  party  shall  pay all costs and  expenses  that it incurs  with
respect  to  the  negotiation,  execution,  delivery  and  performance  of  this
Agreement.  If any  action  at law or in  equity  is  necessary  to  enforce  or
interpret the terms of this Agreement, the prevailing party shall be entitled to
reasonable attorney's fees, costs and necessary disbursements in addition to any
other relief to which such party may be entitled.

                  10.9 Amendments and Waivers. Any term of this Agreement may be
amended and the  observance of any term of this  Agreement may be waived (either
generally   or  in  a   particular   instance   and  either   retroactively   or
prospectively),  only with the written consent of the Company and Investor.  Any
amendment or waiver  effected in accordance with this paragraph shall be binding
upon each holder of any  securities  purchased  under this Agreement at the time
outstanding  (including  securities into which such securities are convertible),
each future holder of all such securities, and the Company.

                  10.10  Severability.   If  one  or  more  provisions  of  this
Agreement are held to be  unenforceable  under  applicable  law, such  provision
shall be excluded from this Agreement and the balance of the Agreement  shall be
interpreted  as if such  provision  were so excluded and shall be enforceable in
accordance with its terms.

                  10.11  Entire  Agreement.  This  Agreement  and the  documents
referred  to herein  constitute  the entire  agreement  among the parties and no
party  shall be  liable  or  bound  to any  other  party  in any  manner  by any
warranties,  representations,  or  covenants  except as  specifically  set forth
herein or therein.


                                       23.
<PAGE>

                  IN WITNESS  WHEREOF,  the parties have executed this Agreement
as of the date first above written.

                                     COMPANY



                                     By:    /s/ Charles W. Jepson
                                            -----------------------------
                                     Title: President & CEO
                                            -----------------------------


                                     INVESTOR:



                                     By:    /s/ John T. Chambers
                                            -----------------------------
                                     Title: President & CEO
                                            -----------------------------








               [SIGNATURE PAGE TO COMMON STOCK PURCHASE AGREEMENT]

                                       24.