<PAGE>   1

                                                                  EXHIBIT 10.1.2

                             VINA TECHNOLOGIES, INC.


                                 1998 STOCK PLAN


                            ADOPTED ON MARCH 19, 1998
                    (AMENDED AND RESTATED ON AUGUST 23, 1999)


<PAGE>   2

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                          PAGE NO.
                                                                          --------
<S>     <C>                                                               <C>
SECTION 1.  ESTABLISHMENT AND PURPOSE........................................1

SECTION 2.  ADMINISTRATION...................................................1

   (a)  Committees of the Board of Directors.................................1
   (b)  Authority of the Board of Directors..................................1

SECTION 3.  ELIGIBILITY......................................................1

   (a)  General Rule.........................................................1
   (b)  Ten-Percent Shareholders.............................................1

SECTION 4.  STOCK SUBJECT TO PLAN............................................2

   (a)  Basic Limitation.....................................................2
   (b)  Additional Shares....................................................2

SECTION 5.  TERMS AND CONDITIONS OF AWARDS OR SALES..........................2

   (a)  Stock Purchase Agreement.............................................2
   (b)  Duration of Offers and Nontransferability of Rights..................2
   (c)  Purchase Price.......................................................2
   (d)  Withholding Taxes....................................................3
   (e)  Restrictions on Transfer of Shares and Minimum Vesting...............3
   (f)  Accelerated Vesting..................................................3

SECTION 6.  TERMS AND CONDITIONS OF OPTIONS..................................3

   (a)  Stock Option Agreement...............................................3
   (b)  Number of Shares.....................................................3
   (c)  Exercise Price.......................................................3
   (d)  Withholding Taxes....................................................4
   (e)  Exercisability.......................................................4
   (f)  Accelerated Exercisability...........................................4
   (g)  Basic Term...........................................................4
   (h)  Nontransferability...................................................4
   (i)  Termination of Service (Except by Death).............................4
   (j)  Death of Optionee....................................................5
   (k)  No Rights as a Shareholder...........................................5
   (l)  Modification, Extension and Assumption of Options....................5
   (m)  Restrictions on Transfer of Shares and Minimum Vesting...............6
   (n)  Accelerated Vesting..................................................6
</TABLE>



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<TABLE>
<CAPTION>
<S>     <C>                                                               <C>
SECTION 7.  PAYMENT FOR SHARES...............................................6

   (a)  General Rule.........................................................6
   (b)  Surrender of Stock...................................................6
   (c)  Services Rendered....................................................6
   (d)  Promissory Note......................................................6
   (e)  Exercise/Sale........................................................7
   (f)  Exercise/Pledge......................................................7

SECTION 8.  ADJUSTMENT OF SHARES.............................................7

   (a)  General..............................................................7
   (b)  Mergers and Consolidations...........................................7
   (c)  Reservation of Rights................................................8

SECTION 9.  SECURITIES LAWS REQUIREMENTS.....................................8

   (a)  General..............................................................8
   (b)  Financial Reports....................................................8

SECTION 10.  NO RETENTION RIGHTS.............................................8


SECTION 11.  DURATION AND AMENDMENTS.........................................8

   (a)  Term of the Plan.....................................................8
   (b)  Right to Amend or Terminate the Plan.................................9
   (c)  Effect of Amendment or Termination...................................9

SECTION 12.  DEFINITIONS.....................................................9
</TABLE>


<PAGE>   4

                     VINA TECHNOLOGIES, INC. 1998 STOCK PLAN


SECTION 1. ESTABLISHMENT AND PURPOSE.

      The purpose of the Plan is to offer selected individuals an opportunity to
acquire a proprietary interest in the success of the Company, or to increase
such interest, by purchasing Shares of the Company's Stock. The Plan provides
both for the direct award or sale of Shares and for the grant of Options to
purchase Shares. Options granted under the Plan may include Nonstatutory Options
as well as ISOs intended to qualify under Section 422 of the Code.

      Capitalized terms are defined in Section 12.

SECTION 2. ADMINISTRATION.

      (a)   COMMITTEES OF THE BOARD OF DIRECTORS. The Plan may be administered
by one or more Committees. Each Committee shall consist of two or more members
of the Board of Directors who have been appointed by the Board of Directors.
Each Committee shall have such authority and be responsible for such functions
as the Board of Directors has assigned to it. If no Committee has been
appointed, the entire Board of Directors shall administer the Plan. Any
reference to the Board of Directors in the Plan shall be construed as a
reference to the Committee (if any) to whom the Board of Directors has assigned
a particular function.

      (b)   AUTHORITY OF THE BOARD OF DIRECTORS. Subject to the provisions of
the Plan, the Board of Directors shall have full authority and discretion to
take any actions it deems necessary or advisable for the administration of the
Plan. All decisions, interpretations and other actions of the Board of Directors
shall be final and binding on all Purchasers, all Optionees and all persons
deriving their rights from a Purchaser or Optionee.

SECTION 3. ELIGIBILITY.

      (a)   GENERAL RULE. Only Employees, Outside Directors and Consultants
shall be eligible for the grant of Options or the direct award or sale of
Shares. Only Employees shall be eligible for the grant of ISOs.

      (b)   TEN-PERCENT SHAREHOLDERS. An individual who owns more than 10% of
the total combined voting power of all classes of outstanding stock of the
Company, its Parent or any of its Subsidiaries shall not be eligible for
designation as an Optionee or Purchaser unless (i) the Exercise Price is at
least 110% of the Fair Market Value of a Share on the date of grant, (ii) the
Purchase Price (if any) is at least 100% of the Fair Market Value of a Share and
(iii) in the case of an ISO, such ISO by its terms is not exercisable after the
expiration of five years from the date of grant. For purposes of this Subsection
(b), in determining stock ownership, the attribution rules of Section 424(d) of
the Code shall be applied.



                                       1
<PAGE>   5

SECTION 4. STOCK SUBJECT TO PLAN.

      (a)   BASIC LIMITATION. The aggregate number of Shares that may be issued
under the Plan (upon exercise of Options or other rights to acquire Shares)
shall not exceed 7,628,400(1) Shares, subject to adjustment pursuant to Section
8. Such authorized share reserve is comprised of the number of Shares which
remained available for grant, as of the Plan Effective Date, under the
Predecessor Plan as last approved by the Company's shareholders prior to such
date, including the Shares subject to the outstanding options incorporated into
the Plan and any other shares which would have been available for future option
grants under the Predecessor Plan. The number of Shares that are subject to
Options or other rights outstanding at any time under the Plan shall not exceed
the number of Shares that then remain available for issuance under the Plan. The
Company, during the term of the Plan, shall at all times reserve and keep
available sufficient Shares to satisfy the requirements of the Plan.

      (b)   ADDITIONAL SHARES. In the event that any outstanding Option or other
right for any reason expires or is canceled or otherwise terminated, the Shares
allocable to the unexercised portion of such Option or other right shall again
be available for the purposes of the Plan. In the event that Shares issued under
the Plan are reacquired by the Company pursuant to any forfeiture provision,
right of repurchase or right of first refusal, such Shares shall again be
available for the purposes of the Plan, except that the aggregate number of
Shares which may be issued upon the exercise of ISOs shall in no event exceed
7,628,400 Shares (subject to adjustment pursuant to Section 8).

SECTION 5. TERMS AND CONDITIONS OF AWARDS OR SALES.

      (a)   STOCK PURCHASE AGREEMENT. Each award or sale of Shares under the
Plan (other than upon exercise of an Option) shall be evidenced by a Stock
Purchase Agreement between the Purchaser and the Company. Such award or sale
shall be subject to all applicable terms and conditions of the Plan and may be
subject to any other terms and conditions which are not inconsistent with the
Plan and which the Board of Directors deems appropriate for inclusion in a Stock
Purchase Agreement. The provisions of the various Stock Purchase Agreements
entered into under the Plan need not be identical.

      (b)   DURATION OF OFFERS AND NONTRANSFERABILITY OF RIGHTS. Any right to
acquire Shares under the Plan (other than an Option) shall automatically expire
if not exercised by the Purchaser within 30 days after the grant of such right
was communicated to the Purchaser by the Company. Such right shall not be
transferable and shall be exercisable only by the Purchaser to whom such right
was granted.

      (c)   PURCHASE PRICE. The Purchase Price of Shares to be offered under the
Plan shall not be less than 85% of the Fair Market Value of such Shares, and a
higher percentage may be

--------------
(1) Reflects 1,500,000-share increase approved by the Board of Directors on May
21, 1998 and the 2-for-1 stock split effected July 10, 1998; reflects
3,000,000-share increase approved by the Board of Directors on August 23, 1999.



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<PAGE>   6

required by Section 3(b). Subject to the preceding sentence, the Purchase Price
shall be determined by the Board of Directors at its sole discretion. The
Purchase Price shall be payable in a form described in Section 7.

      (d)   WITHHOLDING TAXES. As a condition to the purchase of Shares, the
Purchaser shall make such arrangements as the Board of Directors may require for
the satisfaction of any federal, state, local or foreign withholding tax
obligations that may arise in connection with such purchase.

      (e)   RESTRICTIONS ON TRANSFER OF SHARES AND MINIMUM VESTING. Any Shares
awarded or sold under the Plan shall be subject to such special forfeiture
conditions, rights of repurchase, rights of first refusal and other transfer
restrictions as the Board of Directors may determine. Such restrictions shall be
set forth in the applicable Stock Purchase Agreement and shall apply in addition
to any restrictions that may apply to holders of Shares generally. In the case
of a Purchaser who is not an officer of the Company, an Outside Director or a
Consultant, any right to repurchase the Purchaser's Shares at the original
Purchase Price (if any) upon termination of the Purchaser's Service shall lapse
at least as rapidly as 20% per year over the five-year period commencing on the
date of the award or sale of the Shares. Any such right may be exercised only
within 90 days after the termination of the Purchaser's Service for cash or for
cancellation of indebtedness incurred in purchasing the Shares.

      (f)   ACCELERATED VESTING. Unless the applicable Stock Purchase Agreement
provides otherwise, any right to repurchase a Purchaser's Shares at the original
Purchase Price (if any) upon termination of the Purchaser's Service shall lapse
and all of such Shares shall become vested if (i) the Company is subject to a
Change in Control before the Purchaser's Service terminates and (ii) the
repurchase right is not assigned to the entity that employs the Purchaser
immediately after the Change in Control or to its parent or subsidiary.

SECTION 6. TERMS AND CONDITIONS OF OPTIONS.

      (a)   STOCK OPTION AGREEMENT. Each grant of an Option under the Plan shall
be evidenced by a Stock Option Agreement between the Optionee and the Company.
Such Option shall be subject to all applicable terms and conditions of the Plan
and may be subject to any other terms and conditions which are not inconsistent
with the Plan and which the Board of Directors deems appropriate for inclusion
in a Stock Option Agreement. The provisions of the various Stock Option
Agreements entered into under the Plan need not be identical.

      (b)   NUMBER OF SHARES. Each Stock Option Agreement shall specify the
number of Shares that are subject to the Option and shall provide for the
adjustment of such number in accordance with Section 8. The Stock Option
Agreement shall also specify whether the Option is an ISO or a Nonstatutory
Option.

      (c)   EXERCISE PRICE. Each Stock Option Agreement shall specify the
Exercise Price. The Exercise Price of an ISO shall not be less than 100% of the
Fair Market Value of a Share on the date of grant, and a higher percentage may
be required by Section 3(b). The Exercise Price of



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a Nonstatutory Option shall not be less than 85% of the Fair Market Value of a
Share on the date of grant, and a higher percentage may be required by Section
3(b). Subject to the preceding two sentences, the Exercise Price under any
Option shall be determined by the Board of Directors at its sole discretion. The
Exercise Price shall be payable in a form described in Section 7.

      (d)   WITHHOLDING TAXES. As a condition to the exercise of an Option, the
Optionee shall make such arrangements as the Board of Directors may require for
the satisfaction of any federal, state, local or foreign withholding tax
obligations that may arise in connection with such exercise. The Optionee shall
also make such arrangements as the Board of Directors may require for the
satisfaction of any federal, state, local or foreign withholding tax obligations
that may arise in connection with the disposition of Shares acquired by
exercising an Option.

      (e)   EXERCISABILITY. Each Stock Option Agreement shall specify the date
when all or any installment of the Option is to become exercisable. In the case
of an Optionee who is not an officer of the Company, an Outside Director or a
Consultant, an Option shall become exercisable at least as rapidly as 20% per
year over the five-year period commencing on the date of the grant. Subject to
the preceding sentence, the exercisability provisions of any Stock Option
Agreement shall be determined by the Board of Directors at its sole discretion.

      (f)   ACCELERATED EXERCISABILITY. Unless the applicable Stock Option
Agreement provides otherwise, all of an Optionee's Options shall become
exercisable in full if (i) the Company is subject to a Change in Control before
the Optionee's Service terminates, (ii) such Options do not remain outstanding,
(iii) such Options are not assumed by the surviving corporation or its parent
and (iv) the surviving corporation or its parent does not substitute options
with substantially the same terms for such Options.

      (g)   BASIC TERM. The Stock Option Agreement shall specify the term of the
Option. The term shall not exceed 10 years from the date of grant, and a shorter
term may be required by Section 3(b). Subject to the preceding sentence, the
Board of Directors at its sole discretion shall determine when an Option is to
expire.

      (h)   NONTRANSFERABILITY. No Option shall be transferable by the Optionee
other than by beneficiary designation, will or the laws of descent and
distribution. An Option may be exercised during the lifetime of the Optionee
only by the Optionee or by the Optionee's guardian or legal representative. No
Option or interest therein may be transferred, assigned, pledged or hypothecated
by the Optionee during the Optionee's lifetime, whether by operation of law or
otherwise, or be made subject to execution, attachment or similar process.

      (i)   TERMINATION OF SERVICE (EXCEPT BY DEATH). If an Optionee's Service
terminates for any reason other than the Optionee's death, then the Optionee's
Options shall expire on the earliest of the following occasions:

            (i)   The expiration date determined pursuant to Subsection (g)
      above;



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            (ii)  The date three months after the termination of the Optionee's
      Service for any reason other than Disability, or such later date as the
      Board of Directors may determine; or

            (iii) The date twelve months after the termination of the Optionee's
      Service by reason of Disability, or such later date as the Board of
      Directors may determine.

The Optionee may exercise all or part of the Optionee's Options at any time
before the expiration of such Options under the preceding sentence, but only to
the extent that such Options had become exercisable before the Optionee's
Service terminated (or became exercisable as a result of the termination) and
the underlying Shares had vested before the Optionee's Service terminated (or
vested as a result of the termination). The balance of such Options shall lapse
when the Optionee's Service terminates. In the event that the Optionee dies
after the termination of the Optionee's Service but before the expiration of the
Optionee's Options, all or part of such Options may be exercised (prior to
expiration) by the executors or administrators of the Optionee's estate or by
any person who has acquired such Options directly from the Optionee by
beneficiary designation, bequest or inheritance, but only to the extent that
such Options had become exercisable before the Optionee's Service terminated (or
became exercisable as a result of the termination) and the underlying Shares had
vested before the Optionee's Service terminated (or vested as a result of the
termination).

      (j)   DEATH OF OPTIONEE. If an Optionee dies while the Optionee is in
Service, then the Optionee's Options shall expire on the earlier of the
following dates:

            (i)   The expiration date determined pursuant to Subsection (g)
      above; or

            (ii)  The date 12 months after the Optionee's death.

All or part of the Optionee's Options may be exercised at any time before the
expiration of such Options under the preceding sentence by the executors or
administrators of the Optionee's estate or by any person who has acquired such
Options directly from the Optionee by beneficiary designation, bequest or
inheritance, but only to the extent that such Options had become exercisable
before the Optionee's death or became exercisable as a result of the death. The
balance of such Options shall lapse when the Optionee dies.

      (k)   NO RIGHTS AS A SHAREHOLDER. An Optionee, or a transferee of an
Optionee, shall have no rights as a shareholder with respect to any Shares
covered by the Optionee's Option until such person becomes entitled to receive
such Shares by filing a notice of exercise and paying the Exercise Price
pursuant to the terms of such Option.

      (l)   MODIFICATION, EXTENSION AND ASSUMPTION OF OPTIONS. Within the
limitations of the Plan, the Board of Directors may modify, extend or assume
outstanding Options or may accept the cancellation of outstanding Options
(whether granted by the Company or another issuer) in return for the grant of
new Options for the same or a different number of Shares and at



                                       5
<PAGE>   9

the same or a different Exercise Price. The foregoing notwithstanding, no
modification of an Option shall, without the consent of the Optionee, impair the
Optionee's rights or increase the Optionee's obligations under such Option.

      (m)   RESTRICTIONS ON TRANSFER OF SHARES AND MINIMUM VESTING. Any Shares
issued upon exercise of an Option shall be subject to such special forfeiture
conditions, rights of repurchase, rights of first refusal and other transfer
restrictions as the Board of Directors may determine. Such restrictions shall be
set forth in the applicable Stock Option Agreement and shall apply in addition
to any restrictions that may apply to holders of Shares generally. In the case
of an Optionee who is not an officer of the Company, an Outside Director or a
Consultant, any right to repurchase the Optionee's Shares at the original
Exercise Price upon termination of the Optionee's Service shall lapse at least
as rapidly as 20% per year over the five-year period commencing on the date of
the option grant. Any such repurchase right may be exercised only within 90 days
after the termination of the Optionee's Service for cash or for cancellation of
indebtedness incurred in purchasing the Shares.

      (n)   ACCELERATED VESTING. Unless the applicable Stock Option Agreement
provides otherwise, any right to repurchase an Optionee's Shares at the original
Exercise Price upon termination of the Optionee's Service shall lapse and all of
such Shares shall become vested if (i) the Company is subject to a Change in
Control before the Optionee's Service terminates and (ii) the repurchase right
is not assigned to the entity that employs the Optionee immediately after the
Change in Control or to its parent or subsidiary.

SECTION 7. PAYMENT FOR SHARES.

      (a)   GENERAL RULE. The entire Purchase Price or Exercise Price of Shares
issued under the Plan shall be payable in cash or cash equivalents at the time
when such Shares are purchased, except as otherwise provided in this Section 7.

      (b)   SURRENDER OF STOCK. To the extent that a Stock Option Agreement so
provides, all or any part of the Exercise Price may be paid by surrendering, or
attesting to the ownership of, Shares that are already owned by the Optionee.
Such Shares shall be surrendered to the Company in good form for transfer and
shall be valued at their Fair Market Value on the date when the Option is
exercised. The Optionee shall not surrender, or attest to the ownership of,
Shares in payment of the Exercise Price if such action would cause the Company
to recognize compensation expense (or additional compensation expense) with
respect to the Option for financial reporting purposes.

      (c)   SERVICES RENDERED. At the discretion of the Board of Directors,
Shares may be awarded under the Plan in consideration of services rendered to
the Company, a Parent or a Subsidiary prior to the award.

      (d)   PROMISSORY NOTE. To the extent that a Stock Option Agreement or
Stock Purchase Agreement so provides, all or a portion of the Exercise Price or
Purchase Price (as the case may be) of Shares issued under the Plan may be paid
with a full-recourse promissory note.



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The Shares shall be pledged as security for payment of the principal amount of
the promissory note and interest thereon. The interest rate payable under the
terms of the promissory note shall not be less than the minimum rate (if any)
required to avoid the imputation of additional interest under the Code. Subject
to the foregoing, the Board of Directors (at its sole discretion) shall specify
the term, interest rate, amortization requirements (if any) and other provisions
of such note.

      (e)   EXERCISE/SALE. To the extent that a Stock Option Agreement so
provides, and if Stock is publicly traded, payment may be made all or in part by
the delivery (on a form prescribed by the Company) of an irrevocable direction
to a securities broker approved by the Company to sell Shares and to deliver all
or part of the sales proceeds to the Company in payment of all or part of the
Exercise Price and any withholding taxes.

      (f)   EXERCISE/PLEDGE. To the extent that a Stock Option Agreement so
provides, and if Stock is publicly traded, payment may be made all or in part by
the delivery (on a form prescribed by the Company) of an irrevocable direction
to pledge Shares to a securities broker or lender approved by the Company, as
security for a loan, and to deliver all or part of the loan proceeds to the
Company in payment of all or part of the Exercise Price and any withholding
taxes.

SECTION 8. ADJUSTMENT OF SHARES.

      (a)   GENERAL. In the event of a subdivision of the outstanding Stock, a
declaration of a dividend payable in Shares, a declaration of an extraordinary
dividend payable in a form other than Shares in an amount that has a material
effect on the Fair Market Value of the Stock, a combination or consolidation of
the outstanding Stock into a lesser number of Shares, a recapitalization, a
spin-off, a reclassification or a similar occurrence, the Board of Directors
shall make appropriate adjustments in one or more of (i) the number of Shares
available for future grants under Section 4, (ii) the number of Shares covered
by each outstanding Option or (iii) the Exercise Price under each outstanding
Option.

      (b)   MERGERS AND CONSOLIDATIONS. In the event that the Company is a party
to a merger or consolidation, outstanding Options shall be subject to the
agreement of merger or consolidation. Such agreement, without the Optionees'
consent, may provide for:

            (i)   The continuation of such outstanding Options by the Company
      (if the Company is the surviving corporation);

            (ii)  The assumption of the Plan and such outstanding Options by the
      surviving corporation or its parent;

            (iii) The substitution by the surviving corporation or its parent of
      options with substantially the same terms for such outstanding Options; or

            (iv)  The cancellation of such outstanding Options without payment
      of any consideration.



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<PAGE>   11

      (c)   RESERVATION OF RIGHTS. Except as provided in this Section 8, an
Optionee or Purchaser shall have no rights by reason of (i) any subdivision or
consolidation of shares of stock of any class, (ii) the payment of any dividend
or (iii) any other increase or decrease in the number of shares of stock of any
class. Any issuance by the Company of shares of stock of any class, or
securities convertible into shares of stock of any class, shall not affect, and
no adjustment by reason thereof shall be made with respect to, the number or
Exercise Price of Shares subject to an Option. The grant of an Option pursuant
to the Plan shall not affect in any way the right or power of the Company to
make adjustments, reclassifications, reorganizations or changes of its capital
or business structure, to merge or consolidate or to dissolve, liquidate, sell
or transfer all or any part of its business or assets.

SECTION 9. SECURITIES LAW REQUIREMENTS.

      (a)   GENERAL. Shares shall not be issued under the Plan unless the
issuance and delivery of such Shares comply with (or are exempt from) all
applicable requirements of law, including (without limitation) the Securities
Act of 1933, as amended, the rules and regulations promulgated thereunder, state
securities laws and regulations, and the regulations of any stock exchange or
other securities market on which the Company's securities may then be traded.

      (b)   FINANCIAL REPORTS. The Company each year shall furnish to Optionees,
Purchasers and shareholders who have received Stock under the Plan its balance
sheet and income statement, unless such Optionees, Purchasers or shareholders
are key Employees whose duties with the Company assure them access to equivalent
information. Such balance sheet and income statement need not be audited.

SECTION 10. NO RETENTION RIGHTS.

      Nothing in the Plan or in any right or Option granted under the Plan shall
confer upon the Purchaser or Optionee any right to continue in Service for any
period of specific duration or interfere with or otherwise restrict in any way
the rights of the Company (or any Parent or Subsidiary employing or retaining
the Purchaser or Optionee) or of the Purchaser or Optionee, which rights are
hereby expressly reserved by each, to terminate his or her Service at any time
and for any reason, with or without cause.

SECTION 11. DURATION AND AMENDMENTS.

      (a)   TERM OF THE PLAN. The Plan, as set forth herein, shall become
effective on the date of its adoption by the Board of Directors, subject to the
approval of the Company's shareholders. In the event that the shareholders fail
to approve the Plan within 12 months after its adoption by the Board of
Directors, any grants of Options or sales or awards of Shares that have already
occurred shall be rescinded, and no additional grants, sales or awards shall be
made thereafter under the Plan. The Plan shall terminate automatically 10 years
after its adoption by the Board of Directors and may be terminated on any
earlier date pursuant to Subsection (b) below.



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<PAGE>   12

      (b)   PREDECESSOR PLAN. The Plan shall serve as the successor to the
Predecessor Plan, and no further option grants shall be made under the
Predecessor Plan after the Plan Effective Date. All options outstanding under
the Predecessor Plan as of the Plan Effective Date shall, immediately upon
approval of the Plan by the Corporation's shareholders, be incorporated into the
Plan and treated as outstanding options under the Plan. However, each
outstanding option so incorporated shall continue to be governed solely by the
terms of the documents evidencing such option, and no provision of the Plan
shall be deemed to affect or otherwise modify the rights or obligations of the
holders of such incorporated options with respect to their acquisition of shares
of Common Stock.

      (c)   RIGHT TO AMEND OR TERMINATE THE PLAN. The Board of Directors may
amend, suspend or terminate the Plan at any time and for any reason; provided,
however, that any amendment of the Plan which increases the number of Shares
available for issuance under the Plan (except as provided in Section 8), or
which materially changes the class of persons who are eligible for the grant of
ISOs, shall be subject to the approval of the Company's shareholders.
Shareholder approval shall not be required for any other amendment of the Plan.

      (d)   AMENDMENTS. On May 21, 1998, the Board of Directors, subject to
shareholder approval, approved an increase of 1,500,000 Shares authorized for
issuance under the Plan, such that the total number of Shares authorized for
issuance increased from 814,200 Shares to 2,314,200 Shares.

      (e)   EFFECT OF AMENDMENT OR TERMINATION. No Shares shall be issued or
sold under the Plan after the termination thereof, except upon exercise of an
Option granted prior to such termination. The termination of the Plan, or any
amendment thereof, shall not affect any Share previously issued or any Option
previously granted under the Plan.

SECTION 12. DEFINITIONS.

      (a)   "BOARD OF DIRECTORS" shall mean the Board of Directors of the
Company, as constituted from time to time.

      (b)   "CHANGE IN CONTROL" shall mean:

            (i)   The consummation of a merger or consolidation of the Company
      with or into another entity or any other corporate reorganization, if more
      than 50% of the combined voting power of the continuing or surviving
      entity's securities outstanding immediately after such merger,
      consolidation or other reorganization is owned by persons who were not
      shareholders of the Company immediately prior to such merger,
      consolidation or other reorganization; or

            (ii)  The sale, transfer or other disposition of all or
      substantially all of the Company's assets.

A transaction shall not constitute a Change in Control if its sole purpose is to
change the state of the Company's incorporation or to create a holding company
that will be owned in substantially



                                       9
<PAGE>   13

the same proportions by the persons who held the Company's securities
immediately before such transaction.

      (c)   "CODE" shall mean the Internal Revenue Code of 1986, as amended.

      (d)   "COMMITTEE" shall mean a committee of the Board of Directors, as
described in Section 2(a).

      (e)   "COMPANY" shall mean Vina Technologies, Inc., a Delaware
corporation.

      (f)   "CONSULTANT" shall mean a person who performs bona fide services for
the Company, a Parent or a Subsidiary as a consultant or advisor, excluding
Employees and Outside Directors.

      (g)   "DISABILITY" shall mean that the Optionee is unable to engage in any
substantial gainful activity by reason of any medically determinable physical or
mental impairment.

      (h)   "EMPLOYEE" shall mean any individual who is a common-law employee of
the Company, a Parent or a Subsidiary.

      (i)   "EXERCISE PRICE" shall mean the amount for which one Share may be
purchased upon exercise of an Option, as specified by the Board of Directors in
the applicable Stock Option Agreement.

      (j)   "FAIR MARKET VALUE" shall mean the fair market value of a Share, as
determined by the Board of Directors in good faith. Such determination shall be
conclusive and binding on all persons.

      (k)   "ISO" shall mean an employee incentive stock option described in
Section 422(b) of the Code.

      (l)   "NONSTATUTORY OPTION" shall mean a stock option not described in
Sections 422(b) or 423(b) of the Code.

      (m)   "OPTION" shall mean an ISO or Nonstatutory Option granted under the
Plan and entitling the holder to purchase Shares.

      (n)   "OPTIONEE" shall mean an individual who holds an Option.

      (o)   "OUTSIDE DIRECTOR" shall mean a member of the Board of Directors who
is not an Employee.

      (p)   "PARENT" shall mean any corporation (other than the Company) in an
unbroken chain of corporations ending with the Company, if each of the
corporations other than the Company owns stock possessing 50% or more of the
total combined voting power of all classes of stock in one of the other
corporations in such chain. A corporation that attains the status of a



                                       10
<PAGE>   14

Parent on a date after the adoption of the Plan shall be considered a Parent
commencing as of such date.

      (q)   "PLAN" shall mean this Vina Technologies, Inc. 1998 Stock Plan.

      (r)   "PLAN EFFECTIVE DATE" shall mean the date the Board of Directors
adopted the Plan.

      (s)   "PREDECESSOR PLAN" shall mean the Company's Stock Incentive Plan.

      (t)   "PURCHASE PRICE" shall mean the consideration for which one Share
may be acquired under the Plan (other than upon exercise of an Option), as
specified by the Board of Directors.

      (u)   "PURCHASER" shall mean an individual to whom the Board of Directors
has offered the right to acquire Shares under the Plan (other than upon exercise
of an Option).

      (v)   "SERVICE" shall mean service as an Employee, Outside Director or
Consultant.

      (w)   "SHARE" shall mean one share of Stock, as adjusted in accordance
with Section 8 (if applicable).

      (x)   "STOCK" shall mean the Common Stock of the Company.

      (y)   "STOCK OPTION AGREEMENT" shall mean the agreement between the
Company and an Optionee which contains the terms, conditions and restrictions
pertaining to the Optionee's Option.

      (z)   "STOCK PURCHASE AGREEMENT" shall mean the agreement between the
Company and a Purchaser who acquires Shares under the Plan which contains the
terms, conditions and restrictions pertaining to the acquisition of such Shares.

      (aa)  "SUBSIDIARY" means any corporation (other than the Company) in an
unbroken chain of corporations beginning with the Company, if each of the
corporations other than the last corporation in the unbroken chain owns stock
possessing 50% or more of the total combined voting power of all classes of
stock in one of the other corporations in such chain. A corporation that attains
the status of a Subsidiary on a date after the adoption of the Plan shall be
considered a Subsidiary commencing as of such date.



                                       11
<PAGE>   15
                                                                 EXHIBIT 10.1.2b

                 VINA TECHNOLOGIES, INC. 1998 STOCK OPTION PLAN:

                            SUMMARY OF STOCK PURCHASE


By your signature and the signature of the Company's representative below, you
and the Company agree that you are purchasing shares subject to the terms and
conditions of the 1998 Stock Option Plan and the Stock Purchase Agreement, both
of which are attached to and made a part of this document.


      Name of Purchaser:                  <<Name>>

      Total Number of Purchased Shares:   <<TotalShares>>

      Purchase Price Per Share:           $<<PricePerShare>>

      Date of Purchase:                   <<DatePurchase>>

      Vesting Commencement Date:          <<VestComDate>>

      Vesting Schedule:                   The Right of Repurchase shall lapse
                                          with respect to the first<<Percent>>%
                                          of the Purchased Shares when the
                                          Purchaser
                                          completes<<CliffPeriod>>months of
                                          continuous Service after the Vesting
                                          Commencement Date. The Right of
                                          Repurchase shall lapse with respect to
                                          an additional<<Fraction>>% of the
                                          Purchased Shares when the Purchaser
                                          completes each month of continuous
                                          Service thereafter.


PURCHASER:                                VINA TECHNOLOGIES, INC.


                                          By:
----------------------------------           ----------------------------------

                                          Title:
----------------------------------              -------------------------------
Print Name


<PAGE>   16

                 VINA TECHNOLOGIES, INC. 1998 STOCK OPTION PLAN:

                            STOCK PURCHASE AGREEMENT


SECTION 1. ACQUISITION OF SHARES.

      (a)   TRANSFER. On the terms and conditions set forth in the Summary of
Stock Purchase and this Agreement, the Company agrees to transfer to the
Purchaser the number of Shares set forth in the Summary of Stock Purchase. The
transfer shall occur at the offices of the Company on the date of purchase set
forth in the Summary of Stock Purchase or at such other place and time as the
parties may agree.

      (b)   CONSIDERATION. The Purchaser agrees to pay the Purchase Price set
forth in the Summary of Stock Purchase for each Purchased Share. The Purchase
Price is agreed to be at least 100% of the Fair Market Value of the Purchased
Shares. Payment shall be made on the transfer date in cash or cash equivalents.

      (c)   STOCK OPTION PLAN AND DEFINED TERMS. The transfer of the Purchased
Shares is subject to the Plan, a copy of which the Purchaser acknowledges having
received. The provisions of the Plan are incorporated into this Agreement by
this reference. Capitalized terms are defined in Section 12 of this Agreement.

SECTION 2. RIGHT OF REPURCHASE.

      (a)   SCOPE OF REPURCHASE RIGHT. All Purchased Shares initially shall be
Restricted Shares and shall be subject to a right (but not an obligation) of
repurchase by the Company. The Purchaser shall not transfer, assign, encumber or
otherwise dispose of any Restricted Shares, except as provided in the following
sentence. The Purchaser may transfer Restricted Shares (i) by beneficiary
designation, will or intestate succession or (ii) to the Purchaser's spouse,
children or grandchildren or to a trust established by the Purchaser for the
benefit of the Purchaser or the Purchaser's spouse, children or grandchildren,
provided in either case that the Transferee agrees in writing on a form
prescribed by the Company to be bound by all provisions of this Agreement. If
the Purchaser transfers any Restricted Shares, then this Section 2 shall apply
to the Transferee to the same extent as to the Purchaser.

      (b)   CONDITION PRECEDENT TO EXERCISE. The Right of Repurchase shall be
exercisable only during the 60-day period next following the date when the
Purchaser's Service terminates for any reason, with or without cause, including
(without limitation) death or disability.

      (c)   LAPSE OF REPURCHASE RIGHT. The Right of Repurchase shall lapse with
respect to the Purchased Shares in accordance with the vesting schedule set
forth in the Summary of Stock Purchase. In addition, the Right of Repurchase
shall lapse and all of the remaining


<PAGE>   17

Restricted Shares shall become vested if (i) the Company is subject to a Change
in Control before the Purchaser's Service terminates and (ii) the Right of
Repurchase is not assigned to the entity that employs the Purchaser immediately
after the Change in Control or to its parent or subsidiary.

      (d)   REPURCHASE COST. If the Company exercises the Right of Repurchase,
it shall pay the Purchaser an amount equal to the Purchase Price for each of the
Restricted Shares being repurchased.

      (e)   EXERCISE OF REPURCHASE RIGHT. The Right of Repurchase shall be
exercisable only by written notice delivered to the Purchaser prior to the
expiration of the 60-day period specified in Subsection (b) above. The notice
shall set forth the date on which the repurchase is to be effected. Such date
shall not be more than 30 days after the date of the notice. The certificate(s)
representing the Restricted Shares to be repurchased shall, prior to the close
of business on the date specified for the repurchase, be delivered to the
Company properly endorsed for transfer. The Company shall, concurrently with the
receipt of such certificate(s), pay to the Purchaser the purchase price
determined according to Subsection (d) above. Payment shall be made in cash or
cash equivalents or by canceling indebtedness to the Company incurred by the
Purchaser in the purchase of the Restricted Shares. The Right of Repurchase
shall terminate with respect to any Restricted Shares for which it has not been
timely exercised pursuant to this Subsection (e).

      (f)   ADDITIONAL SHARES OR SUBSTITUTED SECURITIES. In the event of the
declaration of a stock dividend, the declaration of an extraordinary dividend
payable in a form other than stock, a spin-off, a stock split, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the
Company's outstanding securities without receipt of consideration, any new,
substituted or additional securities or other property (including money paid
other than as an ordinary cash dividend) which are by reason of such transaction
distributed with respect to any Restricted Shares or into which such Restricted
Shares thereby become convertible shall immediately be subject to the Right of
Repurchase. Appropriate adjustments to reflect the distribution of such
securities or property shall be made to the number and/or class of the
Restricted Shares. Appropriate adjustments shall also, after each such
transaction, be made to the price per share to be paid upon the exercise of the
Right of Repurchase in order to reflect any change in the Company's outstanding
securities effected without receipt of consideration therefor; provided,
however, that the aggregate purchase price payable for the Restricted Shares
shall remain the same.

      (g)   TERMINATION OF RIGHTS AS SHAREHOLDER. If the Company makes
available, at the time and place and in the amount and form provided in this
Agreement, the consideration for the Restricted Shares to be repurchased in
accordance with this Section 2, then after such time the person from whom such
Restricted Shares are to be repurchased shall no longer have any rights as a
holder of such Restricted Shares (other than the right to receive payment of
such consideration in accordance with this Agreement). Such Restricted Shares
shall be deemed to have been repurchased in accordance with the applicable
provisions hereof, whether or not the certificate(s) therefor have been
delivered as required by this Agreement.



                                       2
<PAGE>   18

      (h)   ESCROW. Upon issuance, the certificates for Restricted Shares shall
be deposited in escrow with the Company to be held in accordance with the
provisions of this Agreement. Any new, substituted or additional securities or
other property described in Subsection (f) above shall immediately be delivered
to the Company to be held in escrow, but only to the extent the Purchased Shares
are at the time Restricted Shares. All regular cash dividends on Restricted
Shares (or other securities at the time held in escrow) shall be paid directly
to the Purchaser and shall not be held in escrow. Restricted Shares, together
with any other assets or securities held in escrow hereunder, shall be (i)
surrendered to the Company for repurchase and cancellation upon the Company's
exercise of its Right of Repurchase or Right of First Refusal or (ii) released
to the Purchaser upon the Purchaser's request to the extent the Purchased Shares
are no longer Restricted Shares (but not more frequently than once every six
months). In any event, all Purchased Shares which have vested (and any other
vested assets and securities attributable thereto) shall be released within 60
days after the earlier of (i) the Purchaser's cessation of Service or (ii) the
lapse of the Right of First Refusal.

SECTION 3. RIGHT OF FIRST REFUSAL.

      (a)   RIGHT OF FIRST REFUSAL. In the event that the Purchaser proposes to
sell, pledge or otherwise transfer to a third party any Purchased Shares, or any
interest in such Purchased Shares, the Company shall have the Right of First
Refusal with respect to all (and not less than all) of such Purchased Shares. If
the Purchaser desires to transfer Purchased Shares, the Purchaser shall give a
written Transfer Notice to the Company describing fully the proposed transfer,
including the number of Purchased Shares proposed to be transferred, the
proposed transfer price, the name and address of the proposed Transferee and
proof satisfactory to the Company that the proposed sale or transfer will not
violate any applicable federal or state securities laws. The Transfer Notice
shall be signed both by the Purchaser and by the proposed Transferee and must
constitute a binding commitment of both parties to the transfer of the Purchased
Shares. The Company shall have the right to purchase all, and not less than all,
of the Purchased Shares on the terms of the proposal described in the Transfer
Notice (subject, however, to any change in such terms permitted under Subsection
(b) below) by delivery of a notice of exercise of the Right of First Refusal
within 30 days after the date when the Transfer Notice was received by the
Company. The Company's rights under this Subsection (a) shall be freely
assignable, in whole or in part.

      (b)   TRANSFER OF SHARES. If the Company fails to exercise its Right of
First Refusal within 30 days after the date when it received the Transfer
Notice, the Purchaser may, not later than 90 days following receipt of the
Transfer Notice by the Company, conclude a transfer of the Purchased Shares
subject to the Transfer Notice on the terms and conditions described in the
Transfer Notice, provided that any such sale is made in compliance with
applicable federal and state securities laws and not in violation of any other
contractual restrictions to which the Purchaser is bound. Any proposed transfer
on terms and conditions different from those described in the Transfer Notice,
as well as any subsequent proposed transfer by the Purchaser, shall again be
subject to the Right of First Refusal and shall require compliance with the
procedure described in Subsection (a) above. If the Company exercises its Right
of First Refusal, the parties shall consummate the sale of the Purchased Shares
on the



                                       3
<PAGE>   19

terms set forth in the Transfer Notice within 60 days after the date when the
Company received the Transfer Notice (or within such longer period as may have
been specified in the Transfer Notice); provided, however, that in the event the
Transfer Notice provided that payment for the Purchased Shares was to be made in
a form other than cash or cash equivalents paid at the time of transfer, the
Company shall have the option of paying for the Purchased Shares with cash or
cash equivalents equal to the present value of the consideration described in
the Transfer Notice.

      (c)   ADDITIONAL SHARES OR SUBSTITUTED SECURITIES. In the event of the
declaration of a stock dividend, the declaration of an extraordinary dividend
payable in a form other than stock, a spin-off, a stock split, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the
Company's outstanding securities without receipt of consideration, any new,
substituted or additional securities or other property (including money paid
other than as an ordinary cash dividend) which are by reason of such transaction
distributed with respect to any Purchased Shares subject to this Section 3 or
into which such Purchased Shares thereby become convertible shall immediately be
subject to this Section 3. Appropriate adjustments to reflect the distribution
of such securities or property shall be made to the number and/or class of
Purchased Shares subject to this Section 3.

      (d)   TERMINATION OF RIGHT OF FIRST REFUSAL. Any other provision of this
Section 3 notwithstanding, in the event that the Stock is readily tradable on an
established securities market when the Purchaser desires to transfer Purchased
Shares, the Company shall have no Right of First Refusal, and the Purchaser
shall have no obligation to comply with the procedures prescribed by Subsections
(a) and (b) above.

      (e)   PERMITTED TRANSFERS. This Section 3 shall not apply to (i) a
transfer by beneficiary designation, will or intestate succession or (ii) a
transfer to the Purchaser's spouse, children or grandchildren or to a trust
established by the Purchaser for the benefit of the Purchaser or the Purchaser's
spouse, children or grandchildren, provided in either case that the Transferee
agrees in writing on a form prescribed by the Company to be bound by all
provisions of this Agreement. If the Purchaser transfers any Purchased Shares,
either under this Subsection (e) or after the Company has failed to exercise the
Right of First Refusal, then this Section 3 shall apply to the Transferee to the
same extent as to the Purchaser.

      (f)   TERMINATION OF RIGHTS AS SHAREHOLDER. If the Company makes
available, at the time and place and in the amount and form provided in this
Agreement, the consideration for the Purchased Shares to be purchased in
accordance with this Section 3, then after such time the person from whom such
Purchased Shares are to be purchased shall no longer have any rights as a holder
of such Purchased Shares (other than the right to receive payment of such
consideration in accordance with this Agreement). Such Purchased Shares shall be
deemed to have been purchased in accordance with the applicable provisions
hereof, whether or not the certificate(s) therefor have been delivered as
required by this Agreement.



                                       4
<PAGE>   20

SECTION 4. OTHER RESTRICTIONS ON TRANSFER.

      (a)   PURCHASER REPRESENTATIONS. In connection with the issuance and
acquisition of Shares under this Agreement, the Purchaser hereby represents and
warrants to the Company as follows:

            (i)   The Purchaser is acquiring and will hold the Purchased Shares
      for investment for his or her account only and not with a view to, or for
      resale in connection with, any "distribution" thereof within the meaning
      of the Securities Act.

            (ii)  The Purchaser understands that the Purchased Shares have not
      been registered under the Securities Act by reason of a specific exemption
      therefrom and that the Purchased Shares must be held indefinitely, unless
      they are subsequently registered under the Securities Act or the Purchaser
      obtains an opinion of counsel, in form and substance satisfactory to the
      Company and its counsel, that such registration is not required. The
      Purchaser further acknowledges and understands that the Company is under
      no obligation to register the Purchased Shares.

            (iii) The Purchaser is aware of the adoption of Rule 144 by the
      Securities and Exchange Commission under the Securities Act, which permits
      limited public resales of securities acquired in a non-public offering,
      subject to the satisfaction of certain conditions, including (without
      limitation) the availability of certain current public information about
      the issuer, the resale occurring only after the holding period required by
      Rule 144 has been satisfied, the sale occurring through an unsolicited
      "broker's transaction," and the amount of securities being sold during any
      three-month period not exceeding specified limitations. The Purchaser
      acknowledges and understands that the conditions for resale set forth in
      Rule 144 have not been satisfied and that the Company has no plans to
      satisfy these conditions in the foreseeable future.

            (iv)  The Purchaser will not sell, transfer or otherwise dispose of
      the Purchased Shares in violation of the Securities Act, the Securities
      Exchange Act of 1934, or the rules promulgated thereunder, including Rule
      144 under the Securities Act. The Purchaser agrees that he or she will not
      dispose of the Purchased Shares unless and until he or she has complied
      with all requirements of this Agreement applicable to the disposition of
      Purchased Shares and he or she has provided the Company with written
      assurances, in substance and form satisfactory to the Company, that (A)
      the proposed disposition does not require registration of the Purchased
      Shares under the Securities Act or all appropriate action necessary for
      compliance with the registration requirements of the Securities Act or
      with any exemption from registration available under the Securities Act
      (including Rule 144) has been taken and (B) the proposed disposition will
      not result in the contravention of any transfer restrictions applicable to
      the Purchased Shares under the Rules of the California Corporations
      Commissioner.

            (v)   The Purchaser has been furnished with, and has had access to,
      such information as he or she considers necessary or appropriate for
      deciding whether to invest in the Purchased Shares, and the Purchaser has
      had an opportunity to ask questions and



                                       5
<PAGE>   21

      receive answers from the Company regarding the terms and conditions of the
      issuance of the Purchased Shares.

            (vi)  The Purchaser is aware that his or her investment in the
      Company is a speculative investment which has limited liquidity and is
      subject to the risk of complete loss. The Purchaser is able, without
      impairing his or her financial condition, to hold the Purchased Shares for
      an indefinite period and to suffer a complete loss of his or her
      investment in the Purchased Shares.

      (b)   SECURITIES LAW RESTRICTIONS. Regardless of whether the offering and
sale of Shares under the Plan have been registered under the Securities Act or
have been registered or qualified under the securities laws of any state, the
Company at its discretion may impose restrictions upon the sale, pledge or other
transfer of the Purchased Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in
the judgment of the Company, such restrictions are necessary or desirable in
order to achieve compliance with the Securities Act, the securities laws of any
state or any other law.

      (c)   MARKET STAND-OFF. In connection with any underwritten public
offering by the Company of its equity securities pursuant to an effective
registration statement filed under the Securities Act, including the Company's
initial public offering, the Purchaser shall not directly or indirectly sell,
make any short sale of, loan, hypothecate, pledge, offer, grant or sell any
option or other contract for the purchase of, purchase any option or other
contract for the sale of, or otherwise dispose of or transfer, or agree to
engage in any of the foregoing transactions with respect to, any Purchased
Shares without the prior written consent of the Company or its underwriters.
Such restriction (the "Market Stand-Off") shall be in effect for such period of
time following the date of the final prospectus for the offering as may be
requested by the Company or such underwriters. In no event, however, shall such
period exceed 180 days. The Market Stand-Off shall in any event terminate two
years after the date of the Company's initial public offering. In the event of
the declaration of a stock dividend, a spin-off, a stock split, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the
Company's outstanding securities without receipt of consideration, any new,
substituted or additional securities which are by reason of such transaction
distributed with respect to any Shares subject to the Market Stand-Off, or into
which such Shares thereby become convertible, shall immediately be subject to
the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may
impose stop-transfer instructions with respect to the Purchased Shares until the
end of the applicable stand-off period. The Company's underwriters shall be
beneficiaries of the agreement set forth in this Subsection (c). This Subsection
(c) shall not apply to Shares registered in the public offering under the
Securities Act, and the Purchaser shall be subject to this Subsection (c) only
if the directors and officers of the Company are subject to similar
arrangements.

      (d)   RIGHTS OF THE COMPANY. The Company shall not be required to (i)
transfer on its books any Purchased Shares that have been sold or transferred in
contravention of this Agreement or (ii) treat as the owner of Purchased Shares,
or otherwise to accord voting, dividend



                                       6
<PAGE>   22

or liquidation rights to, any transferee to whom Purchased Shares have been
transferred in contravention of this Agreement.

SECTION 5. SUCCESSORS AND ASSIGNS.

            Except as otherwise expressly provided to the contrary, the
provisions of this Agreement shall inure to the benefit of, and be binding upon,
the Company and its successors and assigns and be binding upon the Purchaser and
the Purchaser's legal representatives, heirs, legatees, distributees, assigns
and transferees by operation of law, whether or not any such person has become a
party to this Agreement or has agreed in writing to join herein and to be bound
by the terms, conditions and restrictions hereof.

SECTION 6. NO RETENTION RIGHTS.

            Nothing in this Agreement or in the Plan shall confer upon the
Purchaser any right to continue in Service for any period of specific duration
or interfere with or otherwise restrict in any way the rights of the Company (or
any Parent or Subsidiary employing or retaining the Purchaser) or of the
Purchaser, which rights are hereby expressly reserved by each, to terminate his
or her Service at any time and for any reason, with or without cause.

SECTION 7. TAX ELECTION.

            The acquisition of the Purchased Shares may result in adverse tax
consequences that may be avoided or mitigated by filing an election under Code
Section 83(b). Such election may be filed only within 30 days after the date of
purchase set forth in the Summary of Stock Purchase. The form for making the
Code Section 83(b) election is attached to this Agreement as an Exhibit. THE
PURCHASER SHOULD CONSULT WITH HIS OR HER TAX ADVISOR TO DETERMINE THE TAX
CONSEQUENCES OF ACQUIRING THE PURCHASED SHARES AND THE ADVANTAGES AND
DISADVANTAGES OF FILING THE CODE SECTION 83(b) ELECTION. THE PURCHASER
ACKNOWLEDGES THAT IT IS HIS OR HER SOLE RESPONSIBILITY, AND NOT THE COMPANY'S,
TO FILE A TIMELY ELECTION UNDER CODE SECTION 83(b), EVEN IF THE PURCHASER
REQUESTS THE COMPANY OR ITS REPRESENTATIVES TO MAKE THIS FILING ON HIS OR HER
BEHALF.

SECTION 8. LEGENDS.

            All certificates evidencing Purchased Shares shall bear the
following legends:

      "THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED,
      ENCUMBERED OR IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH THE
      TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER
      OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH
      AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF FIRST REFUSAL UPON AN
      ATTEMPTED



                                       7
<PAGE>   23

      TRANSFER OF THE SHARES AND CERTAIN REPURCHASE RIGHTS UPON TERMINATION OF
      SERVICE WITH THE COMPANY. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN
      REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT
      CHARGE."

      "THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
      SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
      OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH
      ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL,
      THAT SUCH REGISTRATION IS NOT REQUIRED."

If required by the authorities of any state in connection with the issuance of
the Purchased Shares, the legend or legends required by such state authorities
shall also be endorsed on all such certificates.

SECTION 9. NOTICE.

            Any notice required by the terms of this Agreement shall be given in
writing and shall be deemed effective upon personal delivery or upon deposit
with the United States Postal Service, by registered or certified mail, with
postage and fees prepaid. Notice shall be addressed to the Company at its
principal executive office and to the Purchaser at the address that he or she
most recently provided to the Company.

SECTION 10. ENTIRE AGREEMENT.

            The Summary of Stock Purchase, this Agreement and the Plan
constitute the entire contract between the parties hereto with regard to the
subject matter hereof. They supersede any other agreements, representations or
understandings (whether oral or written and whether express or implied) which
relate to the subject matter hereof.

SECTION 11. CHOICE OF LAW.

            This Agreement shall be governed by, and construed in accordance
with, the laws of the State of California, as such laws are applied to contracts
entered into and performed in such State.

SECTION 12. DEFINITIONS.

      (a)   "AGREEMENT" shall mean this Stock Purchase Agreement.

      (b)   "BOARD OF DIRECTORS" shall mean the Board of Directors of the
Company, as constituted from time to time or, if a Committee has been appointed,
such Committee.



                                       8
<PAGE>   24

      (c)   "CHANGE IN CONTROL" shall mean:

            (i)   The consummation of a merger or consolidation of the Company
      with or into another entity or any other corporate reorganization, if more
      than 50% of the combined voting power of the continuing or surviving
      entity's securities outstanding immediately after such merger,
      consolidation or other reorganization is owned by persons who were not
      shareholders of the Company immediately prior to such merger,
      consolidation or other reorganization; or

            (ii)  The sale, transfer or other disposition of all or
      substantially all of the Company's assets.

            A transaction shall not constitute a Change in Control if its sole
purpose is to change the state of the Company's incorporation or to create a
holding company that will be owned in substantially the same proportions by the
persons who held the Company's securities immediately before such transaction.

            (d)   "CODE" shall mean the Internal Revenue Code of 1986, as
amended.

            (e)   "COMMITTEE" shall mean a committee of the Board of Directors,
as described in Section 2 of the Plan.

            (f)   "COMPANY" shall mean Vina Technologies, Inc., a California
corporation.

            (g)   "CONSULTANT" shall mean a person who performs bona fide
services for the Company, a Parent or a Subsidiary as a consultant or advisor,
excluding Employees and Outside Directors.

            (h)   "EMPLOYEE" shall mean any individual who is a common-law
employee of the Company, a Parent or a Subsidiary.

            (i)   "FAIR MARKET VALUE" shall mean the fair market value of a
Share, as determined by the Board of Directors in good faith. Such determination
shall be conclusive and binding on all persons.

            (j)   "OUTSIDE DIRECTOR" shall mean a member of the Board of
Directors who is not an Employee.

            (k)   "PARENT" shall mean any corporation (other than the Company)
in an unbroken chain of corporations ending with the Company, if each of the
corporations other than the Company owns stock possessing 50% or more of the
total combined voting power of all classes of stock in one of the other
corporations in such chain.

            (l)   "PLAN" shall mean the Vina Technologies, Inc. 1998 Stock
Option Plan, as amended.



                                       9
<PAGE>   25

            (m)   "PURCHASED SHARES" shall mean the Shares purchased by the
Purchaser pursuant to this Agreement.

            (n)   "PURCHASE PRICE" shall mean the amount for which one Share may
be purchased pursuant to this Agreement, as specified in the Summary of Stock
Purchase.

            (o)   "PURCHASER" shall mean the individual named in the Summary of
Stock Purchase.

            (p)   "RESTRICTED SHARE" shall mean a Purchased Share that is
subject to the Right of Repurchase.

            (q)   "RIGHT OF FIRST REFUSAL" shall mean the Company's right of
first refusal described in Section 3.

            (r)   "RIGHT OF REPURCHASE" shall mean the Company's right of
repurchase described in Section 2.

            (s)   "SECURITIES ACT" shall mean the Securities Act of 1933, as
amended.

            (t)   "SERVICE" shall mean service as an Employee, Outside Director
or Consultant.

            (u)   "SHARE" shall mean one share of Stock, as adjusted in
accordance with Section 8 of the Plan (if applicable).

            (v)   "STOCK" shall mean the Common Stock of the Company.

            (w)   "SUBSIDIARY" shall mean any corporation (other than the
Company) in an unbroken chain or corporations beginning with the Company, if
each of the corporations other than the last corporation in the unbroken chain
owns stock possessing 50% or more of the total combined voting power of all
classes of stock in one of the other corporations in such chain.

            (x)   "SUMMARY OF STOCK PURCHASE" shall mean the document so
entitled to which this Agreement is attached.

            (y)   "TRANSFEREE" shall mean any person to whom the Purchaser has
directly or indirectly transferred any Purchased Share.

            (z)   "TRANSFER NOTICE" shall mean the notice of a proposed transfer
of Purchased Shares described in Section 3.



                                       10
<PAGE>   26

                                                                       EXHIBIT I


                             SECTION 83(b) ELECTION

This statement is made under Section 83(b) of the Internal Revenue Code of 1986,
as amended, pursuant to Treasury Regulations Section 1.83-2.

(1)   The taxpayer who performed the services is:

      Name:

      Address:

      Social Security No.:

(2)   The property with respect to which the election is made is ______ shares
      of the common stock of Vina Technologies, Inc.

(3)   The property was transferred on ________ __, 199_.

(4)   The taxable year for which the election is made is the calendar year 199_.

(5)   The property is subject to a repurchase right pursuant to which the issuer
      has the right to acquire the property at the original purchase price if
      for any reason taxpayer's service with the issuer is terminated. The
      issuer's repurchase right lapses in a series of installments over a
      ______-year period ending on ___________ __, _____.

(6)   The fair market value of such property at the time of transfer (determined
      without regard to any restriction other than a restriction which by its
      terms will never lapse) is $___ per share.

(7)   The amount paid for such property is $____ per share.

(8)   A copy of this statement was furnished to Vina Technologies, Inc., for
      whom taxpayer rendered the services underlying the transfer of such
      property.

(9)   This statement is executed on _______ __, 199__.



----------------------------------        -------------------------------------
Spouse (if any)                           Taxpayer

This election must be filed with the Internal Revenue Service Center with which
the Purchaser files his or her Federal income tax returns and must be filed
within 30 days after the date of purchase. This filing should be made by
registered or certified mail, return receipt requested. The Purchaser must
retain two copies of the completed form for filing with his or her Federal and
state tax returns for the current tax year and an additional copy for his or her
records.