<PAGE>   1
                                                                 EXHIBIT 10.6


                           WARRANT ISSUANCE AGREEMENT


      THIS WARRANT ISSUANCE AGREEMENT (the "Agreement") is made effective as of
December 16, 1999, by and between Accelerated Networks, Inc., a California
corporation (the "Company") and Siemens Information and Communication Networks,
Inc., a Delaware corporation (the "Purchaser").

                                 R E C I T A L S

      A.    Company develops and manufactures certain network integration
products ("Products").

      B.    Purchaser desires to purchase Products from the Company, and the
Company and Purchaser have entered into an Agreement for Purchase of Products
dated January 21, 1999 (the "OEM Agreement") pursuant to which Purchaser may
purchase Products from the Company;

      C.    To provide an incentive to Purchaser to purchase its Products,
Company desires to issue Purchaser warrants to purchase the Company's Common
Stock, based on the amount of Products purchased by Purchaser pursuant to
purchase orders issued under the OEM Agreement.

                                A G R E E M E N T

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth herein and for good and valuable consideration, the receipt of which
is hereby acknowledged, the parties hereby agree as follows:

      1.    Issuance of Warrants.

            1.1   Warrants. Subject to the terms and conditions of this
Agreement, Company agrees to issue to Purchaser at each Determination Date (as
defined below), a warrant ("Warrant") to purchase shares of Common Stock of the
Company. The form of each such Warrant shall be as set forth in Exhibit A
hereto. The exercise price for, and the number of shares of, Common Stock
issuable upon exercise of each Warrant shall be determined pursuant to Sections
1.3 and 1.4 below, respectively. Notwithstanding anything to the contrary
herein, the aggregate number of shares of Common Stock issuable pursuant to the
Warrants issued under this Agreement shall not exceed 150,000 (as adjusted for
stock splits, dividends and recapitalizations, and excluding any additional
shares issuable pursuant to anti-dilution adjustments contained herein).

            1.2   Determination Dates. Beginning with the fiscal quarter ending
December 31, 1999 and ending with the fiscal quarter ending December 31, 2000,
the Company shall, within forty-five (45) days after the end of each fiscal
quarter within such period, determine in good faith (each such date of
determination, a "Determination Date") whether Siemens' (as that term is defined
in the OEM Agreement, including its permitted successors and assigns thereunder)
Net Purchases for such fiscal quarter meets or exceeds the applicable Minimum



<PAGE>   2

Threshold. If Siemens' Net Purchases meets or exceeds the applicable Minimum
Threshold, the Company shall promptly issue Purchaser a Warrant to purchase the
number of shares of Common Stock determined pursuant to Section 1.4 at the
exercise price determined pursuant to Section 1.3. As used herein, the "Minimum
Threshold" shall be (a) $4.0 million for the fiscal quarter ending December 31,
1999, (b) $6.0 million for the fiscal quarter ending March 31, 2000, and (c)
$8.0 million for each fiscal quarter ending thereafter, up to and including the
fiscal quarter ending December 31, 2000. Siemens' "Net Purchases" for any fiscal
quarter shall mean the aggregate net purchase price of Products purchased by
Siemens from the Company for such fiscal quarter, based on the date of shipment
by the Company under the terms of the OEM Agreement and of any purchase order
issued by Siemens thereunder; provided, that any purchases made by Siemens
pursuant to that certain Purchase Order No. 8299000014 dated December 16, 1999
shall be deemed to have been made for the fiscal quarter ending December 31,
1999, even if the Products subject to such purchase order are shipped after
December 31, 1999. If the Net Purchases for a fiscal quarter do not meet or
exceed the applicable Minimum Threshold for such fiscal quarter, such purchases
shall not be credited towards any future fiscal quarter in determining whether
the Minimum Threshold for such future fiscal quarter is met.

            1.3   Exercise Price. If, on any Determination Date, the Company is
required, pursuant to Section 1.2, to issue a Warrant to the Purchaser, the
exercise price for each share of Common Stock issuable upon exercise of such
Warrant shall be the price as determined below (as of the Determination Date):

            (a)   If the Common Stock is traded on a securities exchange or
                  through the Nasdaq National Market, the price shall be eighty
                  percent (80%) of the average of the closing prices of the
                  Common Stock on such exchange over the thirty (30) calendar
                  day period ending three (3) days prior to the Determination
                  Date;

            (b)   If the Common Stock is not so traded but is actively traded
                  over-the-counter, the price shall be eighty percent (80%) of
                  the average of the closing bid or sale prices (whichever is
                  applicable) of the Common Stock over the thirty (30) calendar
                  day period ending three (3) days prior to the Determination
                  Date; and

            (c)   If there is no active public market, the price shall be one
                  hundred percent (100%) of the fair market value of the Common
                  Stock, as determined in good faith by a majority of the Board
                  of Directors.

            1.4   Number of Shares. If, on any Determination Date, the Company
is required, pursuant to Section 1.2, to issue a Warrant to the Purchaser, the
number of shares of Common Stock such Warrant shall be exercisable for shall be
determined as follows:

            (a)   If the Determination Date is for the fiscal quarter ended
December 31, 1999, the number of shares shall be equal to the amount determined
by multiplying the Siemens' Net Purchases for such period by 0.05 and dividing
the product thereof by the applicable Exercise Price determined pursuant to
Section 1.3.



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<PAGE>   3

            (b)   If the Determination Date is for any fiscal quarter of the
year 2000, the number of shares shall be equal to the amount determined by
multiplying Siemens' Net Purchases for such period by 0.03 and dividing the
product thereof by the applicable Exercise Price determined pursuant to Section
1.3.

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

            2.1   Organization, Corporate Power and Licenses. The Company is a
corporation duly organized, validly existing and in good standing under the laws
of California and is duly qualified to do business in every jurisdiction in
which the failure to be so qualified would have a material adverse effect on the
business or properties of the Company. The Company possesses all requisite
corporate power and authority and all material licenses, permits and
authorizations necessary to own and operate its properties, to carry on its
business as now conducted and as proposed to be conducted and to carry out the
transactions contemplated by this Agreement.

            2.2   Authorization. The execution, delivery and performance of this
Agreement and the Warrants have been duly authorized by the Company. This
Agreement constitutes, and each of the Warrants issuable hereunder will
constitute, a valid and binding obligation of the Company, enforceable against
the Company in accordance with its terms, subject, as to enforcement of
remedies, to applicable bankruptcy, insolvency, moratorium, reorganization and
similar laws affecting creditors' rights generally and to general equitable
principles.

            2.3   No Conflicts. The execution, delivery and performance by the
Company of this Agreement and compliance herewith and the sale and issuance of
the Warrants and the shares of Common Stock issuable upon exercise of the
Warrants (collectively, the "Securities") will not result in any violation of
and will not conflict with, or result in a breach of any of the terms of, or
constitute a default under, any provision of state or federal law to which the
Company is subject, the Company's Articles of Incorporation or Bylaws, each as
amended, or any provision of any material mortgage, indenture, agreement,
instrument, judgment, decree, order, rule or regulation or other restriction to
which the Company is a party or by which it is bound, the breach of or default
under which would have a material adverse effect upon the Company's business, or
result in the creation of any mortgage, pledge, lien, encumbrance or charge upon
any of the properties or assets of the Company pursuant to any such term;
provided, however, that Securities may be subject to restrictions on transfer
under state and/or federal securities laws and under that certain Investors'
Rights Agreement dated as of May 15, 1998, as amended (the "Rights Agreement"),
among the Company and certain of its shareholders, and that certain Amended and
Restated Voting Agreement dated as of February 24, 1999 (the "Voting
Agreement"), among the Company and certain of its shareholders.

            2.4   Valid Issuance of Stock. The Warrants, when issued and
delivered in accordance with the terms of this Agreement for the consideration
provided for herein, will be, duly and validly issued, fully paid and
nonassessable and will be free of any liens or encumbrances created by the
Company. The shares of Common Stock issuable upon exercise of the Warrants have
been duly and validly reserved for issuance, are not subject to any preemptive



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<PAGE>   4

rights or rights of first refusal, and upon issuance in accordance with the
terms of the Warrants, this Agreement and the Company's Articles of
Incorporation, will be duly and validly issued, fully paid and nonassessable.

            2.5   Governmental Consents. Except for filings of notices required
or permitted to be filed with certain federal and state securities commissions
(which the Company agrees to timely file), no consents, approvals, orders,
authorizations or registrations, qualifications, designations, declarations or
filings with any federal or state governmental authority on the part of the
Company is required in connection with the valid execution, delivery and
performance of this Agreement and the consummation of the transactions
contemplated herein. Based in part on the representations of Purchaser set forth
in Section 3 below, the offer, sale and issuance of the Securities in conformity
with the terms of this Agreement are exempt from the registration and prospectus
delivery requirements of the Securities Act of 1933, as amended (the "Securities
Act"), and have been qualified or are exempt from qualifications under all
applicable state securities qualification requirements.

            2.6   Third Party Consents. Except as set forth above in Section
2.5, all third party consents, approvals, orders or authorizations required to
be obtained by the Company in connection with the consummation of the
transactions contemplated herein have been obtained.

      3.    Representations and Warranties of the Purchaser. The Purchaser
hereby represents and warrants to the Company that:

            3.1   Authorization. It has full power and authority to enter into
this Agreement and this Agreement constitutes its valid and legally binding
obligation, subject, as to enforcement of remedies, to applicable bankruptcy,
insolvency, moratorium, reorganization and similar laws affecting creditors'
rights generally and to general equitable principles.

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

            3.3   Reliance Upon Purchasers' Representations. The Purchaser
understands that the Securities are not registered under the Securities Act on
the ground that the issuance of the Warrants hereunder and the issuance of
Common Stock upon exercise thereof is exempt from registration under the
Securities Act pursuant to section 4(2) thereof, and that the Company's reliance
on such exemption is predicated on the Purchasers' representations set forth
herein. The Purchaser realizes that the basis for the exemption may not be
present if, notwithstanding such representations, the Purchaser has in mind
merely acquiring the Securities for a fixed or determinable period in the
future, or for a market rise, or for sale if the market does not rise. The
Purchaser does not have any such intention.



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<PAGE>   5

            3.4   Receipt of Information. The Purchaser believes it has received
all the information it considers necessary or appropriate for deciding whether
to acquire the Securities. The Purchaser further represents that it has had an
opportunity to ask questions and receive answers from the Company regarding the
terms and conditions of the issuance of the Securities and the business,
properties, prospects and financial condition of the Company and to obtain
additional information (to the extent the Company possessed such information or
could acquire it without unreasonable effort or expense) necessary to verify the
accuracy of any information furnished to it or to which it had access.

            3.5   Investment Experience. The Purchaser represents that it is
experienced in evaluating and investing in securities of companies in the
development stage and acknowledges that it is able to fend for itself, can bear
the economic risk of its investment, and has such knowledge and experience in
financial or business matters that it is capable of evaluating the merits and
risks of the investment in the Securities. Purchaser also represents it has not
been organized for the purpose of acquiring the Securities.

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

            3.7   Restricted Securities. The Purchaser understands that the
Securities may not be sold, transferred, or otherwise disposed of without
registration under the Securities Act or an exemption therefrom, and that in the
absence of an effective registration statement covering the Securities or an
available exemption from registration under the Securities Act, the Securities
must be held indefinitely. In particular, the Purchaser is aware that the
Securities may not be sold pursuant to Rule 144 promulgated under the Securities
Act unless all of the conditions of that Rule are met. Among the conditions for
use of Rule 144 is the availability of current information to the public about
the Company. Such information is not now available and the Company has no
present plans to make such information available.

            3.8   Legends. To the extent applicable, each certificate or other
document evidencing any of the Warrants (and, as applicable, the shares of
Common Stock issued upon exercise of the Warrants) shall be endorsed with the
legends set forth below, and the Purchaser covenants that, except to the extent
such restrictions are waived by the Company, the Purchaser shall not transfer
the Securities represented by any such certificate without complying with the
restrictions on transfer described in the legends endorsed on such certificate:

            (a)   The following legend under the Act:

            "THIS WARRANT AND THE SHARES INTO WHICH IT IS EXERCISABLE
      HAVE NOT BEEN REGISTERED UNDER THE UNITED STATES SECURITIES ACT OF
      1933, AS AMENDED, AND MAY NOT BE SOLD, TRANSFERRED, ASSIGNED,
      PLEDGED, OR HYPOTHECATED ABSENT AN EFFECTIVE REGISTRATION THEREOF
      UNDER SUCH ACT OR COMPLIANCE WITH RULE 144 PROMULGATED UNDER SUCH
      ACT, OR UNLESS THE COMPANY HAS RECEIVED AN OPINION OF COUNSEL,
      SATISFACTORY TO



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<PAGE>   6

      THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT
      REQUIRED.

            (b)   "THE TRANSFER OF THIS WARRANT IS SUBJECT TO
      RESTRICTIONS CONTAINED IN THE WARRANT ISSUANCE AGREEMENT DATED AS
      OF DECEMBER __, 1999, BETWEEN ACCELERATED NETWORKS, INC. AND
      SIEMENS INFORMATION AND COMMUNICATION NETWORKS, INC."

            (c)   Any other legend required by applicable state or federal
      securities laws.

            3.9   Public Sale. Without in any way limiting the representations
set forth above, the Purchaser further agrees not to make any disposition of any
Securities unless and until the transferee has agreed in writing for the benefit
of the Company to be bound by this Section 3.9, the Rights Agreement and the
Voting Agreement; provided, and to the extent, this Section and such agreements
are then applicable, and:

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

            (b)   Purchaser shall have notified the Company of the proposed
disposition and shall have furnished the Company with a detailed statement of
the circumstances surrounding the proposed disposition, and (ii) if reasonably
requested by the Company, Purchaser shall have furnished the Company with an
opinion of counsel, reasonably satisfactory to the Company that such disposition
will not require registration of such shares under the Securities Act. It is
agreed that the Company will not require opinions of counsel from the Purchaser
for transactions made pursuant to Rule 144 under the Securities Act except in
unusual circumstances and will not require opinions of counsel in transactions
involving the transfer or distribution of Securities by the Purchaser to any
direct or indirect subsidiary, parent or affiliate of the Purchaser.

      4.    General Provisions.

            4.1   Construction. This Agreement shall be governed, construed and
enforced in accordance with the internal laws of the State of California.

            4.2   Notices. All payments, notices, requests, demands and other
communications hereunder shall be in writing and shall be deemed to have been
duly given at the earlier of (i) the time of actual delivery or (ii) one day
following the date sent by reputable overnight courier, or (iii) on the third
business day following the date deposited with the United States Postal Service,
postage prepaid, certified with return receipt requested, to the parties at the
following addresses or at such other address as shall be given in writing by a
party to the other parties:

            Purchaser:     Siemens Information and Communication Networks, Inc.
                           900 Broken Sound Parkway
                           Boca Raton, Florida 33487
                           Attn:  Executive Vice President and Chief Financial
                                  Officer



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<PAGE>   7

            The Company:   Accelerated Networks, Inc.
                           301 Science Drive
                           Moorpark, CA  93021
                           Attn:  Chief Financial Officer

            4.3   Successors and Assigns. This Agreement, and the rights or
obligations hereunder, may not be assigned without the prior written consent of
the parties hereto, provided that an assignment by the Company of its rights and
obligations hereunder to any person acquiring the Company by merger or acquiring
all or substantially all of the assets of the Company shall not require the
written consent of the Purchaser (without prejudice to any rights of Purchaser
as a stockholder of the Company or under any other agreement with the Company),
and provided that any assignment by the Purchaser of its rights and obligations
hereunder to any Affiliate of the Purchaser shall not require the written
consent of the Company. As used in this Section 4.3, an "Affiliate" of the
Purchaser shall mean any entity which directly or indirectly wholly owns the
Purchaser, is wholly-owned by the Purchaser, or is under the common ownership of
all of the entities owning, directly or indirectly, all of the interests of each
of the Purchaser and such other entities. An assignment by the Purchaser of its
rights and obligations under this Agreement shall not imply, or be conditioned
on, an assignment (to the same assignee or otherwise) of Siemens' rights and
obligations under the OEM Agreement, the assignability of which shall be
governed by the OEM Agreement. Subject to the foregoing sentence, this Agreement
shall inure to the benefit of, and shall be binding upon, the parties and their
successors and assigns.

            4.4   Severability. If any term, covenant or condition of this
Agreement is held to be invalid, void, or otherwise unenforceable by any court
of competent jurisdiction, the remainder of this Agreement shall not be affected
thereby and each term, covenant and condition of this Agreement shall be valid
and enforceable to the fullest extent permitted by law.

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

            4.6   Amendments and Waivers. Any term of this Agreement may be
amended only with the written consent of the Company and the Purchaser. The
observance of any term of this Agreement may be waived (either generally or in a
particular instance and either retroactively or prospectively), only by the
party who is otherwise adversely affected by the failure to observe such term.
Any amendment or waiver effected in accordance with this paragraph shall be
binding upon each holder of any Securities, each future holder of all such
Securities, and the Company.

            4.7   Each Party to Bear Own Costs. Each of the parties shall pay
all costs and expenses incurred or to be incurred by it in negotiating and
preparing this Agreement and in closing and carrying out the transactions
contemplated by this Agreement.

            4.8   Representation. By executing this Agreement, Purchaser
acknowledges and agrees that Brobeck, Phleger & Harrison LLP represents the
Company solely and that



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<PAGE>   8

Purchaser has had an opportunity to consult with its own attorney and tax
advisor in connection with this Agreement and that Purchaser is responsible for
determining the tax consequences of this transaction on Purchaser.

            4.9   Entire Agreement. This Agreement, together with the agreements
and documents referred to herein, constitute the entire agreement between the
parties hereto with respect to the subject matter hereof and supersede all prior
and contemporaneous agreements and understandings.

            4.10  Option to Terminate. Notwithstanding anything herein to the
contrary, in the event of the transfer of all or substantially all the assets of
the Company to, or consolidation or merger of the Company with or into, any
other entity, such other entity shall have the option to immediately terminate
this Agreement and none of the parties hereto shall have any further obligation
to any other party pursuant to this Agreement; provided, the foregoing shall not
have any force or effect on any previously issued Warrants.



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<PAGE>   9

      IN WITNESS WHEREOF, the undersigned have executed this Agreement to be
effective as of the date first written above.

COMPANY:

ACCELERATED NETWORKS, INC.,
a California corporation

By:   /s/ Frederic T. Boyer
   ----------------------------------
Print Name: Frederic T. Boyer
Title: Chief Financial Officer


PURCHASER:

SIEMENS INFORMATION AND
COMMUNICATION NETWORKS, INC.

By:   /s/ Dieter Diehn
   ----------------------------------
Print Name: Dieter Diehn
Title: Exec. V.P. & CFO

Address:  900 Broken Sound Parkway
          Boca Raton, FL 33487




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<PAGE>   10

                                    EXHIBIT A

                                 FORM OF WARRANT

THE TRANSFER OF THIS WARRANT IS SUBJECT TO RESTRICTIONS CONTAINED IN THE WARRANT
ISSUANCE AGREEMENT DATED AS OF DECEMBER __, 1999, BETWEEN ACCELERATED NETWORKS,
INC. AND SIEMENS INFORMATION AND COMMUNICATION NETWORKS, INC.

THIS WARRANT AND THE SHARES INTO WHICH IT IS EXERCISABLE HAVE NOT BEEN
REGISTERED UNDER THE UNITED STATES SECURITIES ACT OF 1933, AS AMENDED, AND MAY
NOT BE SOLD, TRANSFERRED, ASSIGNED, PLEDGED, OR HYPOTHECATED ABSENT AN EFFECTIVE
REGISTRATION THEREOF UNDER SUCH ACT OR COMPLIANCE WITH RULE 144 PROMULGATED
UNDER SUCH ACT, OR UNLESS THE COMPANY HAS RECEIVED AN OPINION OF COUNSEL,
SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT
REQUIRED.

                           ACCELERATED NETWORKS, INC.

                               Warrant Certificate

Warrant Certificate No. ___



                              VOID AFTER 5:00 P.M.,
                                  PACIFIC TIME
                                December 31, 2001

      THIS CERTIFIES that, for value received, Siemens Information and
Communication Networks, Inc. (the "Holder"), or its permitted assigns hereunder,
is entitled, subject to the terms and conditions set forth below, to purchase
from Accelerated Networks, Inc., a California corporation (hereinafter called
the "Company"), at the Warrant Price (as defined below), from time to time, but
in any event at or prior to 5:00 p.m. Pacific time on December 31, 2001, the
Warrant Shares (as defined below).

      1.    Definitions.

            (a)   The "Warrant Price" shall be $_____ per Warrant Share.

            (b)   The "Warrant Shares" issuable upon exercise of this Warrant
shall be ____ shares of the Company's Common Stock.

            (c)   The "Issuance Date" shall be the date this Warrant is issued
as indicated on the signature page hereof.



                                      A-1
<PAGE>   11

      2.    Exercise of Warrant.

            (a)   The exercise of the purchase rights in whole or in part
evidenced by this Warrant shall be effected by: (a) (i) the surrender of this
Warrant, together with a duly executed copy of the form of Notice of Exercise
attached hereto, to the Company at its principal offices and (ii) the delivery
of the Warrant Price by check or bank draft payable to the Company's order or by
wire transfer in immediately available funds for the number of shares for which
the purchase rights hereunder are being exercised; or (b) the surrender of this
Warrant, together with a duly executed copy of the form of Notice of Net
Exercise attached hereto, to the Company at its principal offices (the "Net
Exercise Right"). Upon exercise of this Net Exercise Right, the Holder shall be
entitled to receive that number of shares of the Company's Common Stock computed
by using the following formula:

                            Y  =  X(A-B)
                                  ------
                                     A

Y  =  the number of Warrant Shares to be issued to the Holder based on this
      exercise.

A  =  the Fair Market Value (as defined below) of one share of the Company's
      Common Stock on the date of exercise of this Warrant.

B  =  The Warrant Price for one Warrant Share under this Warrant.

X  =  The number of Warrant Shares purchasable under this Warrant or, if only
      a portion of the Warrant is being exercised, the portion of the Warrant
      being canceled (at the date of such calculation).

      If the above calculation results in a negative number, then no Warrant
Shares shall be issued or issuable upon exercise of this Warrant pursuant to the
Net Exercise Right.

      "Fair Market Value" of a Warrant Share shall mean:

            (1)   If the Common Stock is traded on a securities exchange or
                  through the Nasdaq National Market, the value shall be deemed
                  to be the average of the closing prices of the Common Stock on
                  such exchange over the thirty (30) calendar day period ending
                  three (3) days prior to the exercise date;

            (2)   If the Common Stock is not so traded but is actively traded
                  over-the-counter, the value shall be deemed to be the average
                  of the closing bid or sale prices (whichever is applicable)
                  over the thirty (30) calendar day period ending three (3) days
                  prior to the exercise date; and

            (3)   If there is no active public market, the value shall be the
                  fair market value thereof, as determined in good faith by a
                  majority of the Board of Directors.



                                      A-2
<PAGE>   12

      In the event of any exercise of the rights represented by this Warrant, a
certificate or certificates for the Warrant Shares so purchased, registered in
the name of the Holder, or its nominee or other party designated in the purchase
form by the Holder hereof, shall be delivered to the Holder as soon as is
reasonably practicable after the date in which the rights represented by this
Warrant shall have been so exercised; and, unless this Warrant has expired or
has been exercised in full, a new Warrant representing the number of shares
(except a remaining fractional share), if any, with respect to which this
Warrant shall not then have been exercised shall also be issued to the Holder
within such time. (All other terms and conditions of such new Warrant shall be
identical to those contained herein, including, but not limited to the effective
date hereof.) The person in whose name any certificate for shares is issued upon
exercise of this Warrant shall for all purposes be deemed to have become the
Holder of record of such shares on the date on which this Warrant was
surrendered and payment of the Warrant Price, except that, if the date of such
surrender and payment is a date on which the stock transfer books of the Company
are closed, such person shall be deemed to have become the Holder of such shares
at the close of business on the next succeeding date on which the stock transfer
books are open. No fractional shares shall be issued upon exercise of this
Warrant and no payment or adjustment shall be made upon any exercise on account
of any cash dividends on the shares issued upon such exercise. If any fractional
interest in a share would, except for the provision of this Section 2, be
delivered upon such exercise, the Company, in lieu of delivery of a fractional
share thereof, shall pay to the Holder an amount in cash equal to the current
fair market value of such fractional share as determined as provided above.

      3.    Stock Splits, Consolidation; Reservation of Shares; Issuance Tax and
Closing of Books.

            3.1   If the Company at any time while this Warrant, or any portion
thereof, remains outstanding and unexpired shall, by stock split, combination,
reclassification or otherwise, change any of the securities as to which purchase
rights under this Warrant exist into the same or a different number of
securities of any other class or classes, this Warrant shall thereafter
represent the right to acquire such number and kind of securities as would have
been issuable as the result of such change with respect to the securities which
were subject to the purchase rights under this Warrant immediately prior to such
stock split, combination, reclassification or other change and the Warrant Price
therefore shall be appropriately adjusted, all subject to further adjustment as
provided herein.

            3.2   The Company will at all times through the expiration of the
Warrant term, reserve and keep available out of its authorized capital stock
solely for the purpose of issue upon the exercise of this Warrant as herein
provided, such number of shares as shall then be issuable upon the exercise of
this Warrant. The Company shall from time to time in accordance with applicable
law increase the authorized amount of its capital stock if at any time the
number of shares remaining unissued and available for issuance shall not be
sufficient to permit exercise of this Warrant. The Company covenants that all
shares which shall be so issued shall be duly and validly issued and fully paid
and nonassessable and free from all taxes, liens and charges with respect to the
issue thereof, and, without limiting such action as may be necessary to assure
that all such shares may be so issued without violation of any applicable law or
regulation, or of any requirement of any national securities exchange upon which
shares of capital stock of the Company may be listed.



                                      A-3
<PAGE>   13

            3.3   The issuance of certificates for shares upon exercise of this
Warrant shall be made without charge to the holder of this Warrant for any
issuance tax in respect thereof provided that the Company shall not be required
to pay any tax which may be payable in respect of any transfer involved in the
issuance and delivery of any certificate in a name other than that of Holder of
this Warrant.

            3.4   The Company will at no time close its transfer books against
the transfer of the shares issued or issuable upon the exercise of this Warrant
in any manner which interferes with the timely exercise of this Warrant.

            3.5   (a)   If the Company shall issue, after the Issuance Date, any
Additional Stock (as defined below) without consideration or for a consideration
per share less than the Warrant Price, the Warrant Price shall forthwith (except
as otherwise provided in this clause (i)) be adjusted to a price determined by
multiplying the then-existing Warrant Price by a fraction, the numerator of
which shall be the number of shares of Common Stock outstanding immediately
prior to such issuance plus the number of shares of Common Stock that the
aggregate consideration received by the Company for such issuance would purchase
at the then-existing Warrant Price; and the denominator of which shall be the
number of shares of Common Stock outstanding immediately prior to such issuance
plus the number of shares of such Additional Stock. Upon any adjustment of the
Warrant Price as provided above, the holder hereof shall thereafter be entitled
to purchase, at the Warrant Price resulting from such adjustment, the number of
shares of Common Stock obtained by multiplying the number of shares of Common
Stock purchasable hereunder immediately prior to such adjustment by a fraction,
the numerator of which is the Warrant Price in effect immediately prior to such
adjustment, and the denominator of which is the Warrant Price resulting from
such adjustment. For purposes of the foregoing computation, the number of shares
of Common Stock outstanding shall be deemed to include all shares of Common
Stock actually outstanding and all shares of Common Stock deemed to be
outstanding as a result of the application of Section 3.5(e).

                  (b)   No adjustment of the Warrant Price shall be made in an
amount less than one cent per share, provided that any adjustments which are not
required to be made by reason of this sentence shall be carried forward and
shall be either taken into account in any subsequent adjustment made prior to 3
years from the date of the event giving rise to the adjustment being carried
forward, or shall be made at the end of 3 years from the date of the event
giving rise to the adjustment being carried forward. Except to the limited
extent provided for in subsections (e)(iii) and (e)(iv), no adjustment of the
Warrant Price pursuant to this Section 3.5 shall have the effect of increasing
the Warrant Price above the Warrant Price in effect immediately prior to such
adjustment.

                  (c)   In the case of the issuance of Common Stock for cash,
the consideration shall be deemed to be the amount of cash paid therefor before
deducting any reasonable discounts, commissions or other expenses allowed, paid
or incurred by the Company for any underwriting or otherwise in connection with
the issuance and sale thereof.

                  (d)   In the case of the issuance of the Common Stock for a
consideration in whole or in part other than cash, the consideration other than
cash shall be



                                      A-4
<PAGE>   14

deemed to be the fair value thereof as determined by the Board of Directors
irrespective of any accounting treatment.

                  (e)   In the case of the issuance of options to purchase or
rights to subscribe for Common Stock, securities by their terms convertible into
or exchangeable for Common Stock or options to purchase or rights to subscribe
for such convertible or exchangeable securities, the following provisions shall
apply for all purposes of this Section 3.5.

                        (i)   The aggregate maximum number of shares of Common
Stock deliverable upon exercise (assuming the satisfaction of any conditions to
exercisability, including without limitation, the passage of time, but without
taking into account potential antidilution adjustments) of such options to
purchase or rights to subscribe for Common Stock shall be deemed to have been
issued at the time such options or rights were issued and for a consideration
equal to the consideration (determined in the manner provided in subsections
3.5(c) and 3.5(d), if any, received by the Company upon the issuance of such
options or rights plus the minimum exercise price provided in such options or
rights (without taking into account potential antidilution adjustments) for the
Common Stock covered thereby.

                        (ii)  The aggregate maximum number of shares of Common
Stock deliverable upon conversion of or in exchange (assuming the satisfaction
of any conditions to convertibility or exchangeability, including, without
limitation, the passage of time, but without taking into account potential
antidilution adjustments) for any such convertible or exchangeable securities or
upon the exercise of options to purchase or rights to subscribe for such
convertible or exchangeable securities and subsequent conversion or exchange
thereof shall be deemed to have been issued at the time such securities were
issued or such options or rights were issued and for a consideration equal to
the consideration, if any, received by the Company for any such securities and
related options or rights (excluding any cash received on account of accrued
interest or accrued dividends), plus the minimum additional consideration, if
any, to be received by the Company (without taking into account potential
antidilution adjustments) upon the conversion or exchange of such securities or
the exercise of any related options or rights (the consideration in each case to
be determined in the manner provided in subsections 3.5(c) and 3.5(d).

                        (iii) In the event of any change in the number of shares
of Common Stock deliverable or in the consideration payable to the Company upon
exercise of such options or rights or upon conversion of or in exchange for such
convertible or exchangeable securities, including, but not limited to, a change
resulting from the antidilution provisions thereof, the Warrant Price, to the
extent in any way affected by or computed using such options, rights or
securities, shall be recomputed to reflect such change, but no further
adjustment shall be made for the actual issuance of Common Stock or any payment
of such consideration upon the exercise of any such options or rights or the
conversion or exchange of such securities.

                        (iv)  Upon the expiration of any such options or rights,
the termination of any such rights to convert or exchange or the expiration of
any options or rights related to such convertible or exchangeable securities,
the Warrant Price, to the extent in any way affected by or computed using such
options, rights or securities or options or rights related



                                      A-5
<PAGE>   15

to such securities, shall be recomputed to reflect the issuance of only the
number of shares of Common Stock (and convertible or exchangeable securities
which remain in effect) actually issued upon the exercise of such options or
rights, upon the conversion or exchange of such securities or upon the exercise
of the options or rights related to such securities.

                        (v)   The number of shares of Common Stock deemed issued
and the consideration deemed paid therefor pursuant to (e)(i) and (e)(ii) shall
be appropriately adjusted to reflect any change, termination or expiration of
the type described in either subsection (e)(iii) or (e)(iv).

                  (f)   "Additional Stock" shall mean any shares of Common Stock
issued (or deemed to have been issued pursuant to Section 3.5(e) by the Company
after the date this Warrant is issued other than

                        (i)   Common Stock issued pursuant to a transaction
described in Section 3.5(g) hereof,

                        (ii)  shares of Common Stock or Common Stock Equivalents
(as defined below) issuable or issued to employees, consultants, or directors
(if in transactions with primarily non-financing purposes) of the Company
directly or pursuant to a stock option plan or restricted stock plan approved by
the Board of Directors of the Company,

                        (iii) shares of Common Stock or Common Stock Equivalents
issued in connection with a bona fide business acquisition of or by the Company
approved by the Board of Directors, whether by merger, consolidation, sale of
assets, sale or exchange of stock or otherwise,

                        (iv)  shares of Common Stock or Common Stock Equivalents
issued in connection with a bona fide lease transaction or bank financing
approved by the Board of Directors,

                        (v)   shares of Common Stock or Common Stock Equivalents
issued to persons or entities with which the Company has a potential or existing
customer or supplier relationship, so long as such issuance is approved by the
Board of Directors, or

                        (vi)  shares of Common Stock issued or issuable in a
public offering in connection with which all outstanding shares of the Company's
Preferred Stock will be converted to Common Stock.

                  (g)   In the event the Company should at any time or from time
to time after the Issuance Date fix a record date for the effectuation of a
split or subdivision of the outstanding shares of Common Stock or the
determination of holders of Common Stock entitled to receive a dividend or other
distribution payable in additional shares of Common Stock or other securities or
rights convertible into, or entitling the holder thereof to receive directly or
indirectly, additional shares of Common Stock (hereinafter referred to as
"Common Stock Equivalents") without payment of any consideration by such holder
for the additional shares of



                                      A-6
<PAGE>   16

Common Stock or the Common Stock Equivalents (including the additional shares of
Common Stock issuable upon conversion or exercise thereof), then, as of such
record date (or the date of such dividend distribution, split or subdivision if
no record date is fixed), the Warrant Price shall be appropriately decreased so
that the number of shares of Common Stock issuable on exercise of this Warrant
shall be increased in proportion to such increase of the aggregate of shares of
Common Stock outstanding and those issuable with respect to such Common Stock
Equivalents with the number of shares issuable with respect to Common Stock
Equivalents determined from time to time in the manner provided for deemed
issuances in Section 3.5(e).

                  (h)   If the number of shares of Common Stock outstanding at
any time after the Issuance Date is decreased by a combination of the
outstanding shares of Common Stock, then, following the record date of such
combination, the Warrant Price shall be appropriately increased so that the
number of shares of Common Stock issuable on exercise of this Warrant shall be
decreased in proportion to such decrease in outstanding shares.

                  (i)   In the event the Company shall declare a distribution
payable in securities of other persons, evidences of indebtedness issued by the
Company or other persons, assets (excluding cash dividends) or options or rights
not referred to in Section 3.5(g), then, in each such case for the purpose of
this Section 3.5(i), the Holder shall be entitled to a proportionate share of
any such distribution as though it were the holder of the number of shares of
Common Stock of the Company into which this Warrant is exercisable as of the
record date fixed for the determination of the holders of Common Stock of the
Company entitled to receive such distribution.

                  (j)   If at any time or from time to time there shall be a
recapitalization of the Common Stock (other than a subdivision, combination or
merger or sale of assets transaction) provision shall be made so that the Holder
shall thereafter be entitled to receive upon exercise of this Warrant the number
of shares of stock or other securities or property of the Company or otherwise,
to which a holder of Common Stock deliverable upon exercise would have been
entitled on such recapitalization. In any such case, appropriate adjustment
shall be made in the application of the provisions of this Section 3.5(j) with
respect to the rights of the Holder after the recapitalization to the end that
the provisions of this Section 3.5(j) (including adjustment of the Warrant Price
then in effect and the number of shares purchasable upon exercise of this
Warrant) shall be applicable after that event as nearly equivalent as may be
practicable.

                  (k)   In case of any reclassification, change or conversion of
securities in the class issuable upon exercise of this Warrant (other than a
change in par value, or from par value to no par value, or from no par value to
par value, or as a result of a subdivision or combination), or in case of any
merger of the Company with or into another corporation (other than a merger with
another corporation in which the Company is a continuing corporation and which
does not result in any reclassification or change of outstanding securities
issuable upon exercise of this Warrant), or in case of any sale of all or
substantially all of the assets of the Company, unless this Warrant shall have
been exercised or terminated in accordance with its terms, the Holder of this
Warrant shall continue to have the right to exercise this Warrant in accordance
with its terms and upon such exercise to receive, in lieu of each share of
Common



                                      A-7
<PAGE>   17

Stock theretofore issuable upon exercise of this Warrant, the kind and amount of
shares of stock, other securities, money and property receivable upon such
reclassification, change or merger by a holder of one share of Common Stock. The
provisions of this subparagraph shall similarly apply to successive
reclassifications, changes, mergers and transfers.

                  (l)   Within fifteen (15) days following the occurrence of
each adjustment or readjustment of the Warrant Price pursuant to this Section 3,
the Company, at its expense, shall promptly compute such adjustment or
readjustment in accordance with the terms hereof and prepare and furnish to the
Holder a certificate setting forth such adjustment or readjustment and showing
in detail the facts upon which such adjustment or readjustment is based. The
Company shall, upon the written request at any time of the Holder, furnish or
cause to be furnished to the Holder a like certificate setting forth (A) such
adjustment and readjustment, (B) the Warrant Price at the time in effect, and
(C) the number of shares of Common Stock and the amount, if any, of other
property which at the time would be received upon the exercise of the Warrant.

      4.    Notice of Record Dates. In the event of:

            4.1   any taking by the Company of a record of the holders of any
class of securities for the purpose of determining the holders thereof who are
entitled to receive any dividend or other distribution (other than cash
dividends out of earned surplus), or any right to subscribe for, purchase or
otherwise acquire any shares of stock of any class or any other securities or
property, or to receive any other right, or

            4.2   any capital reorganization of the Company, any
reclassification or recapitalization of the capital stock of the Company or any
transfer of all or substantially all the assets of the Company to or
consolidation or merger of the Company with or into any other entity, or

            4.3   any voluntary or involuntary dissolution, liquidation or
winding-up of the Company,

            4.4   then and in each such event the Company will give notice to
the Holder of this Warrant specifying (i) the date on which any such record is
to be taken for the purpose of such dividend, distribution or right and stating
the amount and character of such dividend, distribution or right, and (ii) the
date on which any such reorganization, reclassification, recapitalization,
transfer, consolidation, merger, dissolution, liquidation or winding-up is to
take place, and the time, if any is to be fixed, as of which the Holders of
record will be entitled to exchange their shares for securities or other
property deliverable upon such reorganization, reclassification,
recapitalization, transfer, consolidation, merger, dissolution, liquidation or
winding-up. Such notice shall be given at least 20 days and not more than 90
days prior to the date therein specified, and such notice shall state that the
action in question or the record date is subject to the effectiveness of a
registration statement under the Securities Act of 1933, as amended (the
"Securities Act") or to a favorable vote of stockholder, if either is required.

      5.    No Stock Rights or Liabilities. Except as expressly provided herein,
this Warrant shall not entitle the Holder to any voting rights or other rights
as a stockholder of the Company.



                                      A-8
<PAGE>   18

No provision hereof, in the absence of actual exercise hereof by the holder
hereof as provided herein, and no mere enumeration hereon of the rights or
privileges of the Holder hereof, shall give rise to any liability of such Holder
for the Warrant Price or as a stockholder of the Company, whether such liability
is asserted by the Company or by creditors of the Company.

      6.    Notice of Proposed Transfers. The Holder, by acceptance hereof,
agrees to comply in all respects with the provisions of Section 3.9 of the
Warrant Issuance Agreement with respect to this Warrant and any Warrant Shares
issued upon exercise thereof.

      7.    Lost, Stolen, Mutilated or Destroyed Warrant. If this Warrant is
lost, stolen, mutilated or destroyed, the Company shall, on such terms as to
indemnity or otherwise as it may in its discretion reasonably impose (which
shall, in the case of a mutilated Warrant, include the surrender thereof), issue
a new Warrant of like denomination and tenor as the Warrant so lost, stolen,
mutilated or destroyed. Any such new Warrant shall constitute an original
contractual obligation of the Company, whether or not the allegedly lost,
stolen, mutilated or destroyed Warrant shall be at any time enforceable by
anyone.

      8.    Presentment. Prior to due presentment of this Warrant together with
a completed assignment form attached hereto for registration of transfer, the
Company may deem and treat the Holder as the absolute owner of the Warrant,
notwithstanding any notation of ownership or other writing thereon, for the
purpose of any exercise thereof and for all other purposes, and the Company
shall not be affected by any notice to the contrary.

      9.    Notice. Notice or demand pursuant to this Warrant shall be
sufficiently given or made, in accordance with the notice provisions set forth
in Section 4.2 of the Warrant Issuance Agreement.

            9.1   Disputes. If the parties are unable, after good faith
negotiations, which each hereby covenants to undertake, to resolve any dispute
arising between them within fifteen (15) days after notice is given of such
dispute, then the dispute will be referred to arbitration (which the parties
agree is the exclusive means of resolving any such dispute) before one (1)
arbitrator in Los Angeles County, California, or any other place mutually agreed
upon by the parties hereto, in accordance with the applicable commercial
arbitration rules then in effect of the American Arbitration Association (the
"AAA Rules") (or any other form of arbitration mutually acceptable to the
parties). The determination made in accordance with the AAA Rules shall be
delivered in writing to the parties hereto and shall be final, binding and
conclusive on the parties hereto, and the amount of the claim, if any,
determined to exist shall be a valid claim and no further remedy shall be
available to either party with respect to such dispute and judgment may be
entered upon such decision in accordance with applicable law in any court having
jurisdiction thereof. The arbitration award shall include (i) a provision that
the prevailing party in such arbitration recover its costs relating to the
arbitration and reasonable attorneys' fees from the other party, (ii) the amount
of such costs and fees, and (iii) an order that the losing party pay the fees
and expenses of the arbitrator.

      10.   Governing Law. The validity, interpretation and performance of this
Warrant shall be governed by the laws of the State of California without regard
to principles of conflicts of laws.



                                      A-9
<PAGE>   19

      11.   Successors, Assigns. Subject to the restrictions on transfer by
Holder set forth in Section 7 hereof and in the Warrant Issuance Agreement, all
the terms and provisions of the Warrant shall be binding upon and inure to the
benefit of and be enforceable by the respective successors and assigns of the
parties hereto.

      12.   Amendment. This Warrant is one of a series of warrants being issued
pursuant to that certain Warrant Issuance Agreement dated as of December ____,
1999 (the "Warrant Issuance Agreement"). This Warrant may be modified or amended
only by a writing signed by the Company and the holder of this Warrant.

      13.   Severability. Should any part but not the whole of this Warrant for
any reason be declared invalid, such decision shall not affect the validity of
any remaining portion, which remaining portion shall remain in force and effect
as if this Warrant had been executed with the invalid portion thereof
eliminated, and it is hereby declared the intention of the parties hereto that
they would have executed the remaining portion of this Warrant without including
therein any such part which may, for any reason, be hereafter declared invalid.

      IN WITNESS WHEREOF, the Company has caused this Warrant to be duly
executed and delivered on and as of the day and year first above written by one
of its officers thereunto duly authorized.

Dated:  December ___, 1999                ACCELERATED NETWORKS, INC.
                                          a California corporation


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



                                      A-10
<PAGE>   20





                     [SIGNATURE PAGE TO WARRANT CERTIFICATE]







                                      A-11
<PAGE>   21

                               NOTICE OF EXERCISE


(To be executed by the Warrant holder if he desires to exercise the Warrant in
whole or in part)


To:   ACCELERATED NETWORKS, INC.


      The undersigned, whose Social Security or other identifying number is
_____________, hereby irrevocably elects the right of purchase represented by
the within warrant for, and to purchase thereunder, ___________________________
___________________shares of securities provided for therein and tenders payment
herewith to the order of





                           ACCELERATED NETWORKS, INC.

                                in the amount of




                                $_______________




The undersigned requests that certificates for such shares be issued as follows:


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

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

Deliver to:
           --------------------------------------------------------------------

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



                                      A-12
<PAGE>   22

and, if said number of shares shall not be all the shares purchasable hereunder,
that a new Warrant for the balance remaining of the shares purchasable under the
within Warrant be registered in the name of, and delivered to, the undersigned
at the address stated below:


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

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

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


Dated:                      , 19
      ----------------------    ----





                                          Signature:
                                                    ---------------------------

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

                                          (Signature must conform in all
                                          respects to the name of the Warrant
                                          holder as specified on the face of
                                          the Warrant, without alternation,
                                          enlargement or any change whatsoever)



                                      A-13
<PAGE>   23

                             NOTICE OF NET EXERCISE

To:   Accelerated Networks, Inc.
      301 Science Drive
      Moorpark, CA  _________.

            1.    The undersigned hereby elects to exercise that portion of the
attached Warrant representing the right to purchase __________________ shares of
Common Stock of Accelerated Networks, Inc. ("Accelerated") and thereby acquire
such number of shares of Common Stock as is determined pursuant to Section 2 of
such Warrant, which exercise shall be effected pursuant to the terms of the
attached Warrant.

            2     Please issue a certificate or certificates representing said
shares in the name of the undersigned.

            3.    The undersigned represents that the aforesaid shares being
acquired for the account of the undersigned for investment and not with a view
to, or for resale in connection with, the distribution thereof and that the
undersigned has no present intention of distributing or reselling such shares.

            4.    If exercise of the attached Warrant is in connection with a
merger or initial public offering of Accelerated, exercise shall occur upon the
condition of, and simultaneously with, the consummation of such merger or
initial public offering, as the case may be.


Date:                                     SIEMENS INFORMATION AND
     ------------------------
                                          COMMUNICATION NETWORKS, INC.



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

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

                                          Title:
                                                -------------------------------



                                      A-14