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                                                                    EXHIBIT 10.1


                                VOTING AGREEMENT


         THIS VOTING AGREEMENT (the "Voting Agreement") is entered into as of
May 1, 2000, by and between CLARENT CORPORATION., a Delaware corporation
("Parent"), and __________ ("Stockholder").

                                    RECITALS

         A. Parent, Copper Acquisition Sub, Inc., a Delaware corporation and a
wholly owned subsidiary of Parent ("Merger Sub"), and Aluminum, Inc., a Delaware
corporation (the "Company"), are entering into an Agreement and Plan of Merger
and Reorganization of even date herewith (as amended from time to time, the
"Reorganization Agreement"), which provides (subject to the conditions set forth
therein) for the merger of Merger Sub into the Company (the "Merger").

         B. As a condition to the willingness of Parent and Merger Sub to enter
into the Reorganization Agreement, Parent and Merger Sub have required that
Stockholder enter into this Voting Agreement; and Stockholder is entering into
this Voting Agreement in order to induce Parent and Merger Sub to enter into the
Reorganization Agreement.


                                    AGREEMENT

         The parties to this Voting Agreement, intending to be legally bound,
agree as follows:

SECTION 1.        CERTAIN DEFINITIONS

                  (a) All capitalized terms used but not otherwise defined in
this Voting Agreement have the meanings given to them in the Reorganization
Agreement.

                  (b) "SUBJECT SECURITIES" shall mean: (i) all securities of the
Company (including shares of Company Common Stock and options and other rights
to acquire shares of Company Common Stock) Owned by Stockholder as of the date
of this Voting Agreement; and (ii) all additional securities of the Company
(including any additional shares of Company Common Stock and any additional
options or other rights to acquire shares of Company Common Stock) of which
Stockholder acquires Ownership during the period from the date of this Voting
Agreement through the Expiration Date.

                  (c) Stockholder shall be deemed to "OWN" or to have acquired
"OWNERSHIP" of a security if Stockholder: (i) is the record owner of such
security; or (ii) is the "beneficial owner" (within the meaning of Rule 13d-3
under the Exchange Act) of such security.

                  (d) "EXPIRATION DATE" shall mean the earlier of the date upon
which the Reorganization Agreement is validly terminated or the date upon which
the Effective Time occurs.


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                  (e) The "RECORD DATE" for a particular matter shall be the
date fixed for Persons entitled: (i) to receive notice of, and to vote at, a
meeting of the stockholders of the Company called for the purpose of voting on
such matter; or (ii) to take action by written consent of the stockholders of
the Company with respect to such matter.


SECTION 2.        TRANSFER OF SUBJECT SECURITIES

         2.1 NO DISPOSITION OR ENCUMBRANCE OF SUBJECT SECURITIES. Stockholder
covenants and agrees that, from the date of this Voting Agreement until the
Expiration Date, Stockholder will not, directly or indirectly: (i) offer, sell,
offer to sell, contract to sell, pledge, grant any option to purchase or
otherwise dispose of or transfer (or permit or announce any offer, sale, offer
of sale, contract of sale or grant of any option for the purchase of, or permit
or announce any other disposition or transfer of) any of the Subject Securities,
or any interest in any of the Subject Securities, to any Person other than
Parent; (ii) create or permit to exist any Encumbrance on or otherwise affecting
any of the Subject Securities; or (iii) reduce Stockholder's Ownership of,
interest in or risk relating to any of the Subject Securities.

         2.2 TRANSFER OF VOTING RIGHTS. Stockholder covenants and agrees that,
from the date of this Voting Agreement until the Expiration Date, Stockholder
will not deposit any of the Subject Securities into a voting trust or grant a
proxy or enter into a voting agreement or similar Contract with respect to any
of the Subject Securities.


SECTION 3.        VOTING OF SHARES

         3.1 VOTING AGREEMENT. Stockholder covenants and agrees that, from the
date of this Voting Agreement until the Expiration Date, at any meeting of the
stockholders of the Company, however called, and in any written action by
consent of stockholders of the Company, Stockholder shall (unless otherwise
directed in writing by Parent) cause to be voted all outstanding shares of
capital stock of the Company that (as of the Record Date for any of the matters
referred to in this Section 3.1) are Owned by Stockholder:

                           (i) in favor of the Merger and the adoption of the
         Reorganization Agreement and in favor of each of the other actions
         contemplated by the Reorganization Agreement and any action that could
         reasonably be expected to facilitate the consummation of the Merger;
         and

                           (ii) against the following actions (other than the
         Merger and the other transactions contemplated by the Reorganization
         Agreement): (A) any extraordinary corporate transaction, such as a
         merger, consolidation or other business combination involving any of
         the Acquired Companies; (B) any sale, lease or transfer of a material
         amount of assets of any of the Acquired Companies (other than in the
         ordinary course of business); (C) any reorganization, recapitalization,
         dissolution or liquidation of any of the Acquired Companies; (D) any
         removal of or change in a majority of the board of directors of the
         Company; (E) any amendment to the Company's certificate of
         incorporation; (F) any material change in the capitalization of the
         Company or the


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         Company's corporate structure; and (G) any other action that is
         inconsistent with the Merger or that is intended, or could reasonably
         be expected, to impede, interfere with, delay, postpone, discourage or
         adversely affect the Merger or any of the other transactions
         contemplated by the Reorganization Agreement or this Voting Agreement.

Stockholder shall not, from the date of this Voting Agreement until the
Expiration Date, enter into any agreement or understanding with any Person to
vote or give instructions inconsistent with clause "(i)" or "(ii)" of the
preceding sentence.

         3.2      PROXY.

                  (a) Concurrently with the execution of this Voting Agreement:
(i) Stockholder shall deliver to Parent a proxy in the form attached hereto as
Exhibit A, which shall be irrevocable to the fullest extent permitted by law,
with respect to the shares referred to therein (the "Proxy"); and (ii)
Stockholder shall cause to be delivered to Parent an additional proxy (in the
form attached hereto as Exhibit A) executed on behalf of the record owner of any
outstanding shares of Company Common Stock that are owned beneficially (but are
not owned of record) by Stockholder.

                  (b) After the execution of this Voting Agreement until the
Expiration Date, Stockholder shall execute or cause to be executed such further
proxies as may be requested by Parent with respect to any additional shares of
outstanding capital stock of the Company of which Stockholder acquires
Ownership, and Stockholder shall promptly notify Parent upon acquiring Ownership
of any additional securities of the Company.


SECTION 4.        WAIVER OF APPRAISAL RIGHTS.

         Stockholder hereby irrevocably and unconditionally waives any rights of
appraisal, dissenters' rights or similar rights that Stockholder may have in
connection with the Merger, and Stockholder shall cause to be irrevocably and
unconditionally waived any such rights that any affiliate of Stockholder may
have in connection with the Merger.


SECTION 5.        NO SOLICITATION

         Stockholder covenants and agrees that, during the period commencing on
the date of this Voting Agreement and ending on the Expiration Date, Stockholder
shall not, directly or indirectly, and shall not authorize or permit any
Representative of Stockholder, directly or indirectly, to (i) solicit, initiate,
encourage or induce the making, submission or announcement of any Acquisition
Proposal or take any action that would, individually or in the aggregate,
reasonably be expected to lead to an Acquisition Proposal, (ii) furnish any
information regarding any of the Acquired Companies to any Person in connection
with or in response to an Acquisition Proposal or an inquiry or indication of
interest that could lead to an Acquisition Proposal, (iii) engage in discussions
with any Person with respect to any Acquisition Proposal, (iv) approve, endorse
or recommend any Acquisition Proposal, or (v) enter into any letter of intent or
similar document or any Contract contemplating or otherwise relating to any


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Acquisition Transaction. Stockholder shall immediately cease any existing
discussions with any Person that relate to any Acquisition Proposal. Stockholder
shall promptly (and in no event later than 24 hours after receiving, or
obtaining knowledge of, any Acquisition Proposal, any inquiry or indication of
interest that could reasonably be expected to lead to an Acquisition Proposal or
any request for nonpublic information) advise Parent orally and in writing of
any Acquisition Proposal, any inquiry or indication of interest that could
reasonably be expected to lead to an Acquisition Proposal or any request for
nonpublic information relating to any of the Acquired Companies (including the
identity of the Person making or submitting such Acquisition Proposal, inquiry,
indication of interest or request, and the terms thereof) that is made or
submitted by any Person.


SECTION 6.        REPRESENTATIONS AND WARRANTIES OF STOCKHOLDER

         Stockholder hereby represents and warrants to Parent as follows:

         6.1 AUTHORIZATION, ETC. Stockholder has all requisite power and
capacity to execute and deliver this Voting Agreement and the Proxy and to
perform Stockholder's obligations hereunder and thereunder. This Voting
Agreement and the Proxy have been duly executed and delivered by Stockholder
and, assuming the due authorization, execution and delivery by Parent,
constitute the legal, valid and binding obligations of Stockholder, enforceable
against Stockholder in accordance with their respective terms, subject to (i)
laws of general application relating to bankruptcy, insolvency and the relief of
debtors, and (ii) rules of law governing specific performance, injunctive relief
and other equitable remedies.

         6.2      NO CONFLICTS, REQUIRED FILINGS AND CONSENTS.

                  (a) The execution and delivery of this Voting Agreement and
the Proxy by Stockholder do not, and the performance of this Voting Agreement
and the Proxy by Stockholder will not: (i) conflict with or violate any Legal
Requirement, order, decree or judgment applicable to Stockholder or by which
Stockholder or any of Stockholder's properties is bound or affected; or (ii)
result in any breach of or constitute a default (with notice or lapse of time,
or both) under, or give to others any rights of termination, amendment,
acceleration or cancellation of, or result in the creation of an Encumbrance on
or otherwise affecting any of the Subject Securities pursuant to, any Contract
to which Stockholder is a party or by which Stockholder or any of Stockholder's
properties is bound or affected.

                  (b) The execution and delivery of this Voting Agreement and
the Proxy by Stockholder do not, and the performance of this Voting Agreement
and the Proxy by Stockholder will not, require any Consent of any Person.

         6.3 TITLE TO SUBJECT SECURITIES. As of the date hereof, Stockholder
Owns in the aggregate (including shares owned of record and shares owned
beneficially) the number of outstanding shares of capital stock of the Company
specified below Stockholder's name on the signature page hereof, and the number
of options and other rights to acquire shares of Company Common Stock specified
below Stockholder's name on the signature page hereof, and Stockholder does not
directly or indirectly Own any other securities of the Company.


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         6.4 ACCURACY OF REPRESENTATIONS. The representations and warranties
contained in this Voting Agreement are accurate in all respects as of the date
of this Voting Agreement, will be accurate in all respects at all times through
the Expiration Date and will be accurate in all respects as of the date of the
consummation of the Merger as if made on that date.


SECTION 7.        COVENANTS OF STOCKHOLDER

         Stockholder agrees to cooperate fully with Parent and to execute and
deliver (at Parent's expense) such further documents, certificates, agreements
and instruments and to take such other actions (at Parent's expense) as may be
reasonably requested by Parent to evidence or reflect the transactions
contemplated by this Voting Agreement and to carry out the intent and purposes
of this Voting Agreement.

SECTION 8.        LIMITATIONS

         This Voting Agreement is intended to bind Stockholder only with respect
to the specific matters set forth herein, and shall not prohibit Stockholder
from acting in accordance with his or her fiduciary duties as an officer or
director of the Company. Stockholder will retain at all times the right to vote
Stockholder's Subject Securities, in Stockholder's sole discretion, on all
matters other than those set forth in Section 3.1 which are at any time or from
time to time presented to the Company's stockholders generally.

SECTION 9.        MISCELLANEOUS

         9.1 SURVIVAL OF REPRESENTATIONS, WARRANTIES AND AGREEMENTS. None of the
representations, warranties and agreements made by Stockholder in this Voting
Agreement shall survive the Expiration Date; provided, however that the
termination of this Voting Agreement shall not relieve any party from any
liability for any breach of this Voting Agreement.

         9.2 INDEMNIFICATION. Without in any way limiting any of the rights or
remedies otherwise available to Parent, Stockholder shall hold harmless and
indemnify Parent from and against, and shall compensate and reimburse Parent
for, any loss, damage, injury, decline in value, lost opportunity, liability,
exposure, claim, demand, settlement, judgment, award, fine, penalty, tax, fee,
charge, cost or expense of any nature (whether or not relating to a third party
claim) which is directly or indirectly suffered or incurred at any time by
Parent or any of Parent's affiliates or to which Parent or any of Parent's
affiliates otherwise becomes subject and that arises from any inaccuracy in or
breach of any representation, warranty, covenant or obligation of Stockholder
contained in this Voting Agreement.

         9.3 EXPENSES. All costs and expenses incurred in connection with the
transactions contemplated by this Voting Agreement shall be paid by the party
incurring such costs and expenses.

         9.4 NOTICES. Any notice or other communication required or permitted to
be delivered to any party under this Voting Agreement shall be in writing and
shall be deemed properly delivered, given and received (a) when delivered by
hand, or (b) one business day after sent by


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internationally recognized courier or express delivery service (such as Federal
Express) or by facsimile (with confirmation of receipt), to the address or
facsimile telephone number set forth beneath the name of such party below (or to
such other address or facsimile telephone number as such party shall have
specified in a written notice given to the other parties hereto):

                  if to Stockholder:

                           at the address set forth below Stockholder's
                           signature on the signature page hereto;

                  if to Parent:

                           Clarent Corporation
                           700 Chesapeake Drive
                           Redwood City, CA 94063
                           Facsimile:  (650) 306-7512
                           Attention:  Chief Executive Officer

         9.5 SEVERABILITY. In the event that any term, provision, covenant or
restriction contained in this Voting Agreement, or the application of any such
term, provision, covenant or restriction to any Person or set of circumstances,
shall be determined to be invalid, unlawful, void or unenforceable to any
extent, the remainder of this Voting Agreement, and the application of such
term, provision, covenant or restriction to Persons or circumstances other than
those as to which it is determined to be invalid, unlawful, void or
unenforceable, shall not be impaired or otherwise affected and shall continue to
be valid and enforceable to the fullest extent permitted by law.

         9.6 ENTIRE AGREEMENT; COUNTERPARTS. This Voting Agreement, the Proxy,
the Reorganization Agreement and any Affiliate Agreement between Stockholder and
Parent constitute the entire agreement and supersede all prior agreements and
understandings, both written and oral, between the parties with respect to the
subject matter hereof and thereof. No addition to or modification of any
provision of this Voting Agreement shall be binding upon either party hereto
unless made in writing and signed by both parties hereto. This Voting Agreement
may be executed in several counterparts, each of which shall be deemed an
original and all of which shall constitute one and the same instrument.

         9.7 ASSIGNMENT; BINDING EFFECT. Except as provided herein, neither this
Voting Agreement nor any of the obligations hereunder of Stockholder shall be
assigned or delegated by Stockholder (whether by operation of law or otherwise)
without the prior written consent of Parent. Subject to the preceding sentence,
this Voting Agreement shall be binding upon Stockholder and Stockholder's heirs,
successors and assigns, and shall inure to the benefit of Parent and its
successors and assigns. Without limiting any of the restrictions set forth in
Section 2 or elsewhere in this Voting Agreement, this Voting Agreement shall be
binding upon any Person to whom any Subject Securities are transferred.
Notwithstanding anything contained in this Voting Agreement to the contrary,
nothing in this Voting Agreement, express or implied, is


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intended to confer on any Person, other than Parent and its successors and
assigns, any rights or remedies of any nature.

         9.8 SPECIFIC PERFORMANCE. Stockholder agrees that in the event of any
breach or threatened breach by Stockholder of any material covenant, obligation
or other provision contained in this Voting Agreement, Parent shall be entitled
(in addition to any other remedy that may be available to Parent) to: (a) a
decree or order of specific performance or mandamus to enforce the observance
and performance of such covenant, obligation or other provision; and (b) an
injunction restraining such breach or threatened breach. Stockholder further
agrees that neither Parent nor any other Person shall be required to obtain,
furnish or post any bond or similar instrument in connection with or as a
condition to obtaining any remedy referred to in this Section 9.8, and
Stockholder irrevocably waives any right he or she may have to require the
obtaining, furnishing or posting of any such bond or similar instrument.

         9.9 OTHER AGREEMENTS. Nothing in this Voting Agreement shall limit any
of the rights or remedies of Parent or obligations of Stockholder under any
Affiliate Agreement or under any other agreement between Parent and Stockholder
or any certificate or instrument executed by Stockholder in favor of Parent; and
nothing in the Reorganization Agreement or in any other agreement, certificate
or instrument shall limit any of the rights or remedies of Parent or any of the
obligations of Stockholder under this Voting Agreement.

         9.10 APPLICABLE LAW; JURISDICTION. THIS VOTING AGREEMENT SHALL BE
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF
DELAWARE, REGARDLESS OF THE LAWS THAT MIGHT OTHERWISE GOVERN UNDER APPLICABLE
PRINCIPLES OF CONFLICTS OF LAWS THEREOF. In any action between any of the
parties arising out of or relating to this Voting Agreement or any of the
transactions contemplated by this Voting Agreement: (a) each of the parties
irrevocably and unconditionally consents and submits to the jurisdiction and
venue of the state and federal courts located in the State of Delaware; (b) if
any such action is commenced in any other state or federal court, then, subject
to applicable law, no party shall object to the removal of such action to any
federal court located in the State of Delaware; (c) each of the parties
irrevocably waives the right to trial by jury; and (d) the parties irrevocably
consent to service of process in the manner contemplated by Section 9.4.

         9.11 CONSTRUCTION.

                  (a) For purposes of this Voting Agreement, whenever the
context requires: the singular number shall include the plural, and vice versa;
the masculine gender shall include the feminine and neuter genders; the feminine
gender shall include the masculine and neuter genders; and the neuter gender
shall include masculine and feminine genders.

                  (b) The parties hereto agree that any rule of construction to
the effect that ambiguities are to be resolved against the drafting party shall
not be applied in the construction or interpretation of this Voting Agreement.


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                  (c) As used in this Voting Agreement, the words "include" and
"including," and variations thereof, shall not be deemed to be terms of
limitation, but rather shall be deemed to be followed by the words "without
limitation."

                  (d) Except as otherwise indicated, all references in this
Voting Agreement to "Sections" and "Exhibits" are intended to refer to Sections
of this Voting Agreement and Exhibits to this Voting Agreement.

                  (e) The headings contained in this Voting Agreement are for
convenience of reference only, shall not be deemed to be a part of this Voting
Agreement and shall not be referred to in connection with the construction or
interpretation of this Voting Agreement.


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         IN WITNESS WHEREOF, Parent and Stockholder have caused this Voting
Agreement to be executed as of the date first written above.


                                    CLARENT CORPORATION


                                    By:
                                       -----------------------------------------
                                    Name:  Richard J. Heaps
                                    Title: Chief Operating Officer and Chief
                                           Financial Officer


                                    --------------------------------------------
                                    Name:


                                    Address:
                                            ------------------------------------

                                    --------------------------------------------

                                    --------------------------------------------


                                    Facsimile:
                                              ----------------------------------

                                    Number of outstanding shares of Company
                                    Common Stock owned of record as of the date
                                    of this Voting Agreement:
                                                             -------------------

                                    Number of additional outstanding shares of
                                    Company Common Stock owned beneficially (but
                                    not of record) as of the date of this Voting
                                    Agreement:
                                              ----------------------------------



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                                    Number of options and other rights to
                                    acquire shares of Company Common Stock owned
                                    of record as of the date of this Voting
                                    Agreement:____________________


                                    Number of additional options and other
                                    rights to acquire shares of Company Common
                                    Stock owned beneficially (but not of record)
                                    as of the date of this Voting
                                    Agreement:____________________


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                                    EXHIBIT A

                                IRREVOCABLE PROXY


         The undersigned stockholder of ACT Networks, Inc., a Delaware
corporation (the "Company"), hereby irrevocably (to the fullest extent permitted
by law) appoints and constitutes Jerry Shaw-Yau Chang, Richard J. Heaps and
Clarent Corporation, a Delaware corporation ("Parent"), and each of them, the
attorneys and proxies of the undersigned with full power of substitution and
resubstitution, to the full extent of the undersigned's voting rights on the
matters referred to in the third paragraph of this proxy with respect to (i) the
issued and outstanding shares of capital stock of the Company owned of record by
the undersigned as of the date of this proxy, which shares are specified beneath
the undersigned's signature on the signature page of this proxy and (ii) any and
all other shares of capital stock of the Company which the undersigned may
acquire after the date hereof. (The shares of the capital stock of the Company
referred to in clauses "(i)" and "(ii)" of the immediately preceding sentence
are collectively referred to as the "Shares.") Upon the execution hereof, all
prior proxies given by the undersigned with respect to any of the Shares are
hereby revoked, and no subsequent proxies will be given with respect to any of
the Shares.

         This proxy is irrevocable, is coupled with an interest and is granted
in connection with the Voting Agreement, dated as of the date hereof, between
Parent and the undersigned (the "Voting Agreement"), and is granted in
consideration of Parent entering into the Agreement and Plan of Merger and
Reorganization, dated as of the date hereof, among Parent, Copper Acquisition
Sub, Inc., a Delaware corporation and wholly owned subsidiary of Parent, and the
Company (the "Reorganization Agreement"). Capitalized terms used but not
otherwise defined in this proxy have the meanings given to such terms in the
Reorganization Agreement.

         The attorneys and proxies named above will be empowered, and may
exercise this proxy, to vote the Shares at any time until the earlier of the
date upon which the Reorganization Agreement is validly terminated or the date
upon which the Effective Time occurs (the "Expiration Date") at any meeting of
the stockholders of the Company, however called, or in any action by written
consent of stockholders of the Company:

                           (i) in favor of the Merger and the adoption of the
         Reorganization Agreement and in favor of each of the other actions
         contemplated by the Reorganization Agreement and any action that could
         reasonably be expected to facilitate the consummation of the Merger;
         and

                           (ii) in their discretion, with respect to the
         following actions (other than the Merger and the transactions
         contemplated by the Reorganization Agreement): (A) any extraordinary
         corporate transaction, such as a merger, consolidation or other
         business combination involving any of the Acquired Companies; (B) any
         sale, lease or transfer of a material amount of assets of any of the
         Acquired Companies (other than in the ordinary course of business); (C)
         any reorganization, recapitalization, dissolution or liquidation of any
         of the Acquired Companies; (D) any removal of or change in a majority
         of the board of directors of the Company; (E) any amendment to the
         Company's certificate of


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<PAGE>   12

         incorporation; (F) any material change in the capitalization of the
         Company or the Company's corporate structure; or (G) any other action
         which is intended, or could reasonably be expected to, impede,
         interfere with, delay, postpone, discourage or adversely affect the
         Merger or any of the other transactions contemplated by the
         Reorganization Agreement or the Voting Agreement.

         The undersigned stockholder may vote the Shares on all matters other
than the matters referred to in the preceding paragraph.

         This proxy shall be binding upon the heirs, successors and assigns of
the undersigned (including any transferee of any of the Shares).

         In the event that any term, provision, covenant or restriction
contained in this proxy, or the application of any such term, provision,
covenant or restriction to any Person or set of circumstances, shall be
determined to be invalid, unlawful, void or unenforceable to any extent, the
remainder of this proxy, and the application of such term, provision, covenant
or restriction to Persons or circumstances other than those as to which it is
determined to be invalid, unlawful, void or unenforceable, shall not be impaired
or otherwise affected and shall continue to be valid and enforceable to the
fullest extent permitted by law..

         This proxy shall terminate upon the Expiration Date.

Dated:  May 1, 2000


                                    --------------------------------------------
                                    Name:


                                    Number of shares of Company Common Stock
                                    owned of record as of the date of this
                                    proxy:
                                           -------------------------------------


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