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                                                                   Exhibit 10.23
                              CLARENT CORPORATION

                             EMPLOYMENT AGREEMENT
                                      for
                                 BARRY FORMAN

     This Employment Agreement ("Agreement") is entered into as of the 5th day
of March 2001, by and between Barry Forman ("Executive") and Clarent
Corporation, a Delaware corporation (the "Company").

     Whereas, the Company desires to employ Executive to provide personal
services to the Company, and wishes to provide Executive with certain
compensation and benefits in return for his services; and

     Whereas, Executive wishes to be employed by the Company and provide
personal services to the Company in return for certain compensation;

     Now, Therefore, in consideration of the mutual promises and covenants
contained herein, it is hereby agreed by and between the parties hereto as
follows:

     1.   Employment by the Company.
          --------------------------

          1.1   Subject to the terms set forth herein, the Company agrees to
employ Executive in the position of Executive Chairman, and Executive hereby
accepts such employment, effective as of March 5, 2001 (the "Employment Date").
Executive shall report to the Company's Board of Directors (the "Board").
Executive shall serve in an executive capacity and shall perform such duties as
are directed to him by the Board. During the term of his employment with the
Company, Executive will devote his best efforts and full time and attention
(except for reasonable periods of illness or other incapacities permitted by the
Company's general employment policies) to the business of the Company.

          1.2   Executive's primary office location will be at the Company's
corporate headquarters in Redwood City, California; however, during the time
that he resides in the Seattle, Washington area, Executive may work from his
home office or another Seattle location, so long as he is able to perform
satisfactorily his job duties from such location(s). The Company will provide
Executive with appropriate administrative support staffing for his work from
such Washington location(s).

          1.3   The employment relationship between the parties shall also be
governed by the general employment policies and practices of the Company,
including those relating to protection of confidential information and
assignment of inventions,

                                       1.
<PAGE>

except that when the terms of this Agreement differ from or are in conflict with
the Company's general employment policies or practices, this Agreement shall
control.

     2.   Compensation.
          ------------

          2.1   Salary. Executive shall receive for services to be rendered
                ------
hereunder an annual base salary of $280,000, less required payroll deductions
and withholdings. Executive will be eligible to receive annual adjustments to
his base salary as determined by the Board, or a committee thereof, in its
discretion.

          2.2   Bonus. Executive shall be eligible to receive bonuses based on
                -----
the Company's financial performance. Executive will receive a bonus of $50,000,
less required payroll deductions and withholdings, if the Company fully meets
its revenue ("top line") targets for Fiscal Year 2001. Executive will also
receive, as a separate bonus, a bonus of $100,000, less required payroll
deductions and withholdings, if the Company fully meets its net profit ("bottom
line") targets for Fiscal Year 2001. The top line and bottom line targets
described above will be given to Executive in writing within thirty (30) days
after the date of this Agreement.

          2.3   Stock Option. The Company will grant Executive a stock option
                ------------
("Option") to purchase 600,000 shares of the Company's Common Stock under a plan
or agreement ("Forman Option") approved by the Board. The exercise price of the
Option shares shall be their fair market value at the time of the grant, as
determined by the Board. The Option will vest over four years, with twenty-five
percent (25%) of the shares vesting on the one-year anniversary of the vesting
commencement date, and the remaining shares vesting in equal monthly
installments thereafter. Subject to Sections 5.3 and 5.4 below, vesting of the
Option will cease immediately in the event that Executive's employment
relationship with the Company ends, for any reason, and Executive does not
continue to provide uninterrupted service to the Company as a consultant, and
such vesting shall cease even if Executive continues to serve as a Director on
the Company's Board. During any and all time periods in which Executive provides
service to the Company as an employee or consultant and the Option continues
vesting, he shall not be eligible to receive any stock option grants pursuant to
the Company's 1999 Non-Employee Directors' Stock Option Plan ("Directors
Grants").

          2.4   Benefits. Executive shall be entitled to receive all standard
                --------
Company benefits for which he is eligible and that are provided to the Company's
executive-level employees generally.

          2.5   Car Allowance. Executive shall be entitled to participate in the
                -------------
Company's car allowance program for its executive-level employees.

          2.6   Housing Allowance. During the time that Executive's principal
                -----------------
residence is located in the Seattle, Washington area, the Company will provide
him with suitable living accommodations within a reasonable distance of the
Company's corporate headquarters, at the Company's expense, in the reasonable
determination of the Board.

                                       2.
<PAGE>

          2.7   Vacation. Executive shall be entitled to vacation and illness
                --------
days during the term of this Agreement consistent with the Company's standard
policies and practices for its executive-level employees generally.

     3.   Proprietary Information Obligations.
          -----------------------------------

          3.1   Agreement. Executive agrees to execute and abide by the
                ---------
Proprietary Information and Inventions Agreement in the form attached hereto as
Exhibit A.

          3.2   Remedies. Executive's duties under the Proprietary Information
                --------
and Inventions Agreement shall survive termination of his employment with the
Company. Executive acknowledges that a remedy at law for any breach or
threatened breach by him of the provisions of the Proprietary Information and
Inventions Agreement would be inadequate, and he therefore agrees that the
Company shall be entitled to injunctive relief in case of any such breach or
threatened breach.

     4.   Outside Activities.
          ------------------

          4.1   Except with the prior written consent of the Board, Executive
will not during the term of this Agreement undertake or engage in any other
employment, occupation or business enterprise, other than ones in which he is a
passive investor. Executive may engage in civic and not-for-profit activities so
long as such activities do not materially interfere with the performance of his
duties under this Agreement.

          4.2   Except as permitted by Section 4.3 below, Executive agrees not
to acquire, assume or participate in, directly or indirectly, any position,
investment or interest known by him to be adverse or antagonistic to the
Company, or its business or prospects, financial or otherwise.

          4.3   During the term of his employment by the Company, except on
behalf of the Company, Executive will not directly or indirectly, whether as an
officer, director, stockholder, partner, proprietor, associate, representative,
consultant, or in any capacity whatsoever, become financially interested in, be
employed by, perform services for, or have any business connection with, any
other person, corporation, firm, partnership or other entity whatsoever that
competes directly, or is preparing to engage in competition, with the Company,
throughout the world (collectively, "Competitor"), in any line of business
engaged in (or planned to be engaged in) by the Company; provided, however, that
anything above to the contrary notwithstanding, he may own, as a passive
investor, securities of any Competitor, so long as his direct holdings in any
one such corporation shall not in the aggregate constitute more than 2 percent
of the voting stock of such corporation.

     5.   Term; Termination.
          -----------------

          5.1   The term of this Agreement shall be for no specific period. The
Company may terminate this Agreement and Executive's employment with or without
Cause (as defined below), and Executive may terminate this Agreement and his

                                       3.
<PAGE>

employment with or without Good Reason (as defined below), by giving written
notice of termination to the other party.

          5.2   Subject to Section 5.3 below, in the event Executive's
employment is terminated pursuant to Section 5.1 above or upon his death, the
Company shall be obligated to pay Executive only his accrued and unpaid base
salary and accrued and unused vacation time as of such termination or
resignation date (the "Termination Date"), less required payroll deductions and
withholdings, and no further vesting of Executive's Option shall occur after the
Termination Date unless Executive continues to provide uninterrupted service to
the Company as a consultant; provided, however, that upon cessation of vesting
of the Option, Executive's vested Option shares will be exercisable in
accordance with the exercise periods set forth in the applicable Option
documentation.

          5.3   In the event the Company terminates Executive's employment
without Cause or Executive terminates his employment for Good Reason, including
but not limited to within twelve (12) months after a Change in Control (as
defined below), as Executive's sole severance benefits: (a) the Company shall
pay Executive an amount equal to twelve (12) months of his base salary as of the
Termination Date, subject to standard payroll deductions and withholdings, and
payable, at the Company's sole discretion, either in a lump sum or in twelve
(12) equal monthly installments over the twelve-month period following the
Termination Date; (b) if Executive elects to continue his group health insurance
coverage following his termination pursuant to federal COBRA law, the Company
will reimburse Executive for the cost to continue his health insurance coverage
under COBRA at the same level of coverage in effect during his employment, for
twelve (12) months after the Termination Date, unless and until Executive
becomes eligible to receive comparable benefits from another employer; and (c)
the Company shall, in its sole discretion, either (i) accelerate the vesting of
Executive's unvested Option shares so that an additional twelve (12) months of
vesting will occur as of the Termination Date, or (ii) continue the vesting of
the Option for an additional twelve (12) months from the Termination Date, if
and as permitted by the applicable Option documentation.

          5.4   In the event Executive terminates his employment without Good
Reason after the one year anniversary of the Employment Date, the Company shall
continue the vesting of the Option for twelve (12) months from the Termination
Date; provided, however, that (a) during any such continued vesting period
Executive shall not be eligible to receive any Directors Grants, and (b) any
such continued vesting shall cease immediately as of the date Executive ceases
to serve as a Director on the Company's Board.

Executive agrees that the severance benefits due upon termination of employment
pursuant to Section 5.3 above shall be conditioned on Executive's signing and
delivering to the Company a full general release of claims as against the
Company, its officers, directors, shareholders, employees and agents, in a form
acceptable to the Company.

As used herein "Cause" shall mean Executive's:  (i) unauthorized use or
disclosure of trade secrets of the Company or other material breach of his
Proprietary Information and Inventions Agreement; (ii) conviction of any felony
under the laws of the United States or

                                       4.
<PAGE>

any state thereof; (iii) fraud or dishonesty in carrying out his duties or which
causes harm to the Company; or (iv) persistent failure to adequately perform his
job duties, as determined by the Board in good faith, after providing Executive
with notice of his performance deficiencies and an opportunity to cure such
deficiencies within thirty (30) days of such notice, except that such notice and
opportunity to cure are not required if they would be futile. Executive's
physical or mental disability shall not constitute Cause, except as permitted by
law.

As used herein "Good Reason" shall mean Executive's termination of his
employment for either of the following reasons:  (i) an involuntary reduction in
Executive's base salary; or (ii) an involuntary and material reduction in
Executive's position or job duties.

As used herein "Change in Control" shall have the meaning set forth in Section
8(b) or 8(c) of the Forman Option.

     6.   Golden Parachute Taxes. In the event that the severance and other
          ----------------------
benefits provided to Executive by this Agreement (i) constitute "parachute
payments" within the meaning of Section 280G of the Code, or any comparable
successor provisions, and (ii) but for this paragraph would be subject to the
excise tax imposed by Section 4999 of the Code, or any comparable successor
provisions (the "Excise Tax"), then Executive's benefits hereunder shall be
either

          (i)   provided to Executive in full, or

          (ii)  provided to Executive as to such lesser extent which would
                result in no portion of such benefits being subject to the
                Excise Tax,

whichever of the foregoing amounts, when taking into account applicable federal,
state, local and foreign income and employment taxes, the Excise Tax, and any
other applicable taxes, results in the receipt by Executive, on an after-tax
basis, of the greatest amount of benefits, notwithstanding that all or some
portion of such benefits may be taxable under the Excise Tax. Unless the Company
and Executive agree otherwise in writing, any determination required under this
paragraph shall be made in writing in good faith by a qualified third party (the
"Professional Service Firm"). In the event of a reduction of benefits hereunder
the reduction to zero dollars ($0) of all benefits paid in cash is insufficient
to avoid liability under the Excise Tax., Executive shall be given the choice of
which benefits to reduce. For purposes of making the calculations required by
this paragraph, the Professional Service Firm may make reasonable assumptions
and approximations concerning applicable taxes and may rely on reasonable, good
faith interpretations concerning the application of the Code, and other
applicable legal authority. The Company and Executive shall furnish to the
Professional Service Firm such information and documents as the Professional
Service Firm may reasonably request in order to make a determination under this
Section 6. The Company shall bear all costs the Professional Service Firm may
reasonably incur in connection with any calculations contemplated by this
paragraph.

                                       5.
<PAGE>

If, notwithstanding any reduction described in this paragraph, the Internal
Revenue Service ("IRS") determines that Executive is liable for the Excise Tax
as a result of the receipt of the payment of benefits described above, then
Executive shall be obligated to pay back to the Company, within thirty (30) days
after a final IRS determination or in the event that Executive challenges the
final IRS determination, a final judicial determination, a portion of the
payment equal to the "Repayment Amount." The Repayment Amount with respect to
the payment of benefits shall be the smallest amount, if any, as shall be
required to be paid to the Company so that Executive's net after-tax proceeds
with respect to any payment of benefits (after taking into account the payment
of the Excise Tax and all other applicable taxes imposed on such payment) shall
be maximized. The Repayment Amount with respect to the payment of benefits shall
be zero if a Repayment Amount of more than zero would not result in Executive's
net after-tax proceeds with respect to the payment of such benefits being
maximized. If the Excise Tax is not eliminated pursuant to this paragraph,
Executive shall pay the Excise Tax.

Notwithstanding any other provision of this paragraph, if (i) there is a
reduction in the payment of benefits as described in this paragraph, (ii) the
IRS later determines that Executive is liable for the Excise Tax, the payment of
which would result in the maximization of Executive's net after-tax proceeds
(calculated as if Executive's benefits previously had not been reduced), and
(iii) Executive pays the Excise Tax, then the Company shall pay to Executive
those benefits which were reduced pursuant to this paragraph contemporaneously
or as soon as administratively possible after Executive pays the Excise Tax so
that Executive's net after-tax proceeds with respect to the payment of benefits
is maximized.

     7.   Nonsolicitation. While employed by the Company, and for one (1) year
          ---------------
immediately following the termination of Executive's employment for any reason,
Executive agrees not to solicit, attempt to solicit, induce, or otherwise cause
any employee of the Company to terminate his or her employment in order to
become an employee, consultant or independent contractor of any person or entity
other than the Company.

     8.   General Provisions.
          ------------------

          8.1   Notices. Any notices provided hereunder must be in writing and
                -------
shall be deemed effective upon the earlier of personal delivery (including
personal delivery by facsimile) or the third day after mailing by first class
mail, to the Company at its primary office location and to Executive at his
address as listed on the Company payroll.

          8.2   Severability. Whenever possible, each provision of this
                ------------
Agreement will be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Agreement is held to be invalid,
illegal or unenforceable in any respect under any applicable law or rule in any
jurisdiction, such invalidity, illegality or unenforceability will not affect
any other provision or any other jurisdiction, but this Agreement will be
reformed, construed and enforced in such jurisdiction as if such invalid,
illegal or unenforceable provisions had never been contained herein.

                                       6.
<PAGE>

          8.3   Waiver. If either party should waive any breach of any
                ------
provisions of this Agreement, he or it shall not thereby be deemed to have
waived any preceding or succeeding breach of the same or any other provision of
this Agreement.

          8.4   Complete Agreement. This Agreement and its Exhibit A constitute
                ------------------
the entire agreement between Executive and the Company and it is the complete,
final, and exclusive embodiment of their agreement with regard to this subject
matter. It is entered into without reliance on any promise or representation
other than those expressly contained herein, and it cannot be modified or
amended except in a writing signed by an officer of the Company.

          8.5   Counterparts. This Agreement may be executed in separate
                ------------
counterparts, any one of which need not contain signatures of more than one
party, but all of which taken together will constitute one and the same
Agreement.

          8.6   Headings. The headings of the sections hereof are inserted for
                --------
convenience only and shall not be deemed to constitute a part hereof or to
affect the meaning thereof.

          8.7   Successors and Assigns. This Agreement is intended to bind and
                ----------------------
inure to the benefit of and be enforceable by Executive and the Company, and
their respective successors, assigns, heirs, executors and administrators,
except that Executive may not assign any of his duties hereunder and he may not
assign any of his rights hereunder without the written consent of the Company,
which shall not be withheld unreasonably.

          8.8   Choice of Law. All questions concerning the construction,
                -------------
validity and interpretation of this Agreement will be governed by the law of the
State of California.

     In Witness Whereof, the parties have executed this Agreement on the day and
year first above written.

Clarent Corporation                          Barry Forman



By:  /s/ Jerry Chang                         By:  /s/ Barry Forman
     ----------------------------                 ------------------------------
     Name:  Jerry Chang                               Barry Forman
     Title: President & CEO

Date: March 5, 2001                          Date: March 5, 2001
     ----------------------------                 ------------------------------

                                       7.
<PAGE>

                                   Exhibit A

                              CLARENT CORPORATION

                       EMPLOYEE PROPRIETARY INFORMATION
                           AND INVENTIONS AGREEMENT

          In consideration of my employment or continued employment by Clarent
Corporation (the "Company"), and the compensation now and hereafter paid to me,
I hereby agree as follows:

                               1.  Nondisclosure

     1.1  Recognition of Company's Rights; Nondisclosure. At all times during my
employment and thereafter, I will hold in strictest confidence and will not
disclose, use, lecture upon or publish any of the Company's Proprietary
Information (defined below), except as such disclosure, use or publication may
be required in connection with my work for the Company, or unless an officer of
the Company expressly authorizes such in writing. I will obtain Company's
written approval before publishing or submitting for publication any material
(written, verbal, or otherwise) that relates to my work at Company and/or
incorporates any Proprietary Information. I hereby assign to the Company any
rights I may have or acquire in such Proprietary Information and recognize that
all Proprietary Information shall be the sole property of the Company and its
assigns.

     1.2  Proprietary Information. The term "Proprietary Information" shall mean
any and all confidential and/or proprietary knowledge, data or information of
the Company. By way of illustration but not limitation, "Proprietary
Information" includes (a) trade secrets, inventions, mask works, ideas,
processes, formulas, source and object codes, data, programs, other works of
authorship, know-how, improvements, discoveries, developments, designs and
techniques (hereinafter collectively referred to as "Inventions"); and (b)
information regarding plans for research, development, new products, marketing
and selling, business plans, budgets and unpublished financial statements,
licenses, prices and costs, suppliers and customers; and (c) information
regarding the skills and compensation of other employees of the Company.
Notwithstanding the foregoing, it is understood that, at all such times, I am
free to use information which is generally known in the trade or industry, which
is not gained as result of a breach of this Agreement, and my own, skill,
knowledge, know-how and experience to whatever extent and in whichever way I
wish.

     1.3  Third Party Information. I understand, in addition, that the Company
has received and in the future will receive from third parties confidential or
proprietary information ("Third Party Information") subject to a duty on the
Company's part to maintain the confidentiality of such information and to use it
only for certain limited purposes. During the term of my employment and
thereafter, I will hold Third Party Information in the strictest confidence and
will not disclose to anyone (other than Company personnel who need to know such
information in connection with their work for the Company) or use, except in
connection with my work for the Company, Third Party Information unless
expressly authorized by an officer of the Company in writing.

     1.4  No Improper Use of Information of Prior Employers and Others. During
my employment by the Company I will not improperly use or disclose any
confidential information or trade secrets, if any, of any former employer or any
other person to whom I have an obligation of confidentiality, and I will not
bring onto the premises of the Company any unpublished documents or any property
belonging to any former employer or any other person to whom I have an
obligation of confidentiality unless consented to in writing by that former
employer or person. I will use in the performance of my duties only information
which is generally known and used by persons with training and experience
comparable to my own, which is common knowledge in the industry or otherwise
legally in the public domain, or which is otherwise provided or developed by the
Company.

2.   Assignment of Inventions.

     2.1  Proprietary Rights. The term "Proprietary Rights" shall mean all trade
secret, patent, copyright, mask work and other intellectual property rights
throughout the world.

     2.2  Prior Inventions. Inventions, if any, patented or unpatented, which I
made prior to the commencement of my employment with the Company

                                      A-1
<PAGE>

are excluded from the scope of this Agreement. To preclude any possible
uncertainty, I have set forth on Exhibit B (Previous Inventions) attached hereto
a complete list of all Inventions that I have, alone or jointly with others,
conceived, developed or reduced to practice or caused to be conceived, developed
or reduced to practice prior to the commencement of my employment with the
Company, that I consider to be my property or the property of third parties and
that I wish to have excluded from the scope of this Agreement (collectively
referred to as "Prior Inventions"). If disclosure of any such Prior Invention
would cause me to violate any prior confidentiality agreement, I understand that
I am not to list such Prior Inventions in Exhibit B but am only to disclose a
cursory name for each such invention, a listing of the party(ies) to whom it
belongs and the fact that full disclosure as to such inventions has not been
made for that reason. A space is provided on Exhibit B for such purpose. If no
such disclosure is attached, I represent that there are no Prior Inventions. If,
in the course of my employment with the Company, I incorporate a Prior Invention
into a Company product, process or machine, the Company is hereby granted and
shall have a nonexclusive, royalty-free, irrevocable, perpetual, worldwide
license (with rights to sublicense through multiple tiers of sublicensees) to
make, have made, modify, use and sell such Prior Invention. Notwithstanding the
foregoing, I agree that I will not incorporate, or permit to be incorporated,
Prior Inventions in any Company Inventions without the Company's prior written
consent.

     2.3  Assignment of Inventions. Subject to Sections 2.4, and 2.6, I hereby
assign and agree to assign in the future (when any such Inventions or
Proprietary Rights are first reduced to practice or first fixed in a tangible
medium, as applicable) to the Company all my right, title and interest in and to
any and all Inventions (and all Proprietary Rights with respect thereto) whether
or not patentable or registrable under copyright or similar statutes, made or
conceived or reduced to practice or learned by me, either alone or jointly with
others, during the period of my employment with the Company. Inventions assigned
to the Company, or to a third party as directed by the Company pursuant to this
Section 2, are hereinafter referred to as "Company Inventions."

     2.4  Nonassignable Inventions. This Agreement does not apply to an
Invention which qualifies fully as a nonassignable Invention under Section 2870
of the California Labor Code (hereinafter "Section 2870"). I have reviewed the
notification on Exhibit A (Limited Exclusion Notification) and agree that my
signature acknowledges receipt of the notification.

     2.5  Obligation to Keep Company Informed. During the period of my
employment and for six (6) months after termination of my employment with the
Company, I will promptly disclose to the Company fully and in writing all
Inventions authored, conceived or reduced to practice by me, either alone or
jointly with others. In addition, I will promptly disclose to the Company all
patent applications filed by me or on my behalf within a year after termination
of employment. At the time of each such disclosure, I will advise the Company in
writing of any Inventions that I believe fully qualify for protection under
Section 2870; and I will at that time provide to the Company in writing all
evidence necessary to substantiate that belief. The Company will keep in
confidence and will not use for any purpose or disclose to third parties without
my consent any confidential information disclosed in writing to the Company
pursuant to this Agreement relating to Inventions that qualify fully for
protection under the provisions of Section 2870. I will preserve the
confidentiality of any Invention that does not fully qualify for protection
under Section 2870.

     2.6  Government or Third Party. I also agree to assign all my right, title
and interest in and to any particular Company Invention to a third party,
including without limitation the United States, as directed by the Company.

     2.7  Works for Hire. I acknowledge that all original works of authorship
which are made by me (solely or jointly with others) within the scope of my
employment and which are protectable by copyright are "works made for hire,"
pursuant to United States Copyright Act (17 U.S.C., Section 101).

     2.8  Enforcement of Proprietary Rights. I will assist the Company in every
proper way to obtain, and from time to time enforce, United States and foreign
Proprietary Rights relating to Company Inventions in any and all countries. To
that end I will execute, verify and deliver such documents and perform such
other acts (including appearances as a witness) as the Company may reasonably
request for use in applying for, obtaining, perfecting, evidencing, sustaining
and enforcing such Proprietary Rights and the assignment thereof. In addition, I
will execute, verify and deliver assignments of such Proprietary Rights to the
Company or its designee. My obligation to assist the Company with respect to
Proprietary Rights relating to such Company Inventions in any and all countries
shall continue beyond the termination of my employment, but the Company

                                      A-2
<PAGE>

shall compensate me at a reasonable rate after my termination for the time
actually spent by me at the Company's request on such assistance.

In the event the Company is unable for any reason, after reasonable effort, to
secure my signature on any document needed in connection with the actions
specified in the preceding paragraph, I hereby irrevocably designate and appoint
the Company and its duly authorized officers and agents as my agent and attorney
in fact, which appointment is coupled with an interest, to act for and in my
behalf to execute, verify and file any such documents and to do all other
lawfully permitted acts to further the purposes of the preceding paragraph with
the same legal force and effect as if executed by me. I hereby waive and
quitclaim to the Company any and all claims, of any nature whatsoever, which I
now or may hereafter have for infringement of any Proprietary Rights assigned
hereunder to the Company.

3.   Records. I agree to keep and maintain adequate and current records (in the
form of notes, sketches, drawings and in any other form that may be required by
the Company) of all Proprietary Information developed by me and all Inventions
made by me during the period of my employment at the Company, which records
shall be available to and remain the sole property of the Company at all times.

4.   Additional Activities. I agree that during the period of my employment by
the Company I will not, without the Company's express written consent, engage in
any employment or business activity which is competitive with, or would
otherwise conflict with, my employment by the Company. I agree further that for
the period of my employment by the Company and for one (l) year after the date
of termination of my employment by the Company, I will not directly or
indirectly, on behalf of myself or any other person or entity, solicit, call
upon, divert, take away, or recruit, or attempt to solicit, call upon, divert,
take away, or recruit, any employees, customers, licensors, or licensees of the
Company.

5.   No Conflicting Obligation. I represent that my performance of all the terms
of this Agreement and as an employee of the Company does not and will not breach
any agreement to keep in confidence information acquired by me in confidence or
in trust prior to my employment by the Company. I have not entered into, and I
agree I will not enter into, any agreement either written or oral in conflict
herewith.

6.   Return of Company Documents. When I leave the employ of the Company, I will
deliver to the Company any and all drawings, notes, memoranda, specifications,
devices, formulas, and documents, together with all copies thereof, and any
other material containing or disclosing any Company Inventions, Third Party
Information or Proprietary Information of the Company. I further agree that any
property situated on the Company's premises and owned by the Company, including
disks and other storage media, filing cabinets or other work areas, is subject
to inspection by Company personnel at any time with or without notice. Prior to
leaving, I will cooperate with the Company in completing and signing the
Company's termination statement.

7.   Legal and Equitable Remedies. Because my services are personal and unique
and because I may have access to and become acquainted with the Proprietary
Information of the Company, the Company shall have the right to enforce this
Agreement and any of its provisions by injunction, specific performance or other
equitable relief, without bond and without prejudice to any other rights and
remedies that the Company may have for a breach of this Agreement.

8.   Notices. Any notices required or permitted hereunder shall be given to the
appropriate party at the address specified below or at such other address as the
party shall specify in writing. Such notice shall be deemed given upon personal
delivery to the appropriate address or if sent by certified or registered mail,
three (3) days after the date of mailing.

9.   Notification of New Employer. In the event that I leave the employ of the
Company, I hereby consent to the notification of my new employer of my rights
and obligations under this Agreement.

10.  Insider trading policy. Attached to this Agreement, as Exhibit C, is the
Company's Insider Trading Policy, as may be issued from time to time by the
Company. Upon execution of this Agreement, I acknowledge and agree to adhere to
such Insider Trading Policy.

11.  General Provisions.

     11.1 Governing Law; Consent to Personal Jurisdiction. This Agreement will
be governed by and construed according to the laws of the State of California,
as such laws are applied to agreements entered into and to be performed entirely
within California between California residents. I hereby expressly consent to
the personal jurisdiction of the state and federal courts located in San Mateo
County, California for any lawsuit filed there against me by Company arising
from or related to this Agreement.

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<PAGE>

     11.2 Severability. In case any one or more of the provisions contained in
this Agreement shall, for any reason, be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect the other provisions of this Agreement, and this Agreement
shall be construed as if such invalid, illegal or unenforceable provision had
never been contained herein. If moreover, any one or more of the provisions
contained in this Agreement shall for any reason be held to be excessively broad
as to duration, geographical scope, activity or subject, it shall be construed
by limiting and reducing it, so as to be enforceable to the extent compatible
with the applicable law as it shall then appear.

     11.3 Successors and Assigns. This Agreement will be binding upon my heirs,
executors, administrators and other legal representatives and will be for the
benefit of the Company, its successors, and its assigns.

     11.4 Survival. The provisions of this Agreement shall survive the
termination of my employment and the assignment of this Agreement by the Company
to any successor in interest or other assignee.

     11.5 Employment. I agree and understand that nothing in this Agreement
shall confer any right with respect to continuation of employment by the
Company, nor shall it interfere in any way with my right or the Company's right
to terminate my employment at any time, with or without cause.

     11.6 Waiver. No waiver by the Company of any breach of this Agreement shall
be a waiver of any preceding or succeeding breach. No waiver by the Company of
any right under this Agreement shall be construed as a waiver of any other
right. The Company shall not be required to give notice to enforce strict
adherence to all terms of this Agreement.

     11.7 Entire Agreement. The obligations pursuant to Sections 1 and 2 of this
Agreement shall apply to any time during which I was previously employed, or am
in the future employed, by the Company as a consultant if no other agreement
governs nondisclosure and assignment of inventions during such period. This
Agreement is the final, complete and exclusive agreement of the parties with
respect to the subject matter hereof and supersedes and merges all prior
discussions between us. No modification of or amendment to this Agreement, nor
any waiver of any rights under this Agreement, will be effective unless in
writing and signed by the party to be charged. Any subsequent change or changes
in my duties, salary or compensation will not affect the validity or scope of
this Agreement.

    This Agreement shall be effective as of the first day of my employment with
the Company, namely: 12 March, 2001.

    I have read this Agreement carefully and understand its terms. I have
completely filled out Exhibit B to this Agreement.

Dated:  March 12, 2001
        --------------

/s/ Barry Forman
------------------------------
(Signature)

Barry Forman
------------------------------
(Printed Name)

Accepted and Agreed To:

Clarent Corporation

By: /s/ Julien Nepomucero
    --------------------------

Title: HR Assistant
       -----------------------

 700 Chesapeake Drive
------------------------------
(Address)

Redwood City, CA 94063
------------------------------

Dated: 03/12/01
       -----------------------

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