<PAGE>

                                                                    EXHIBIT 10.7

                                   SUBLEASE
                                   --------

     THIS SUBLEASE (this "Sublease") is dated for reference purposes as of
August 23, 1999, and is made by and between Proxim, Inc., a Delaware corporation
("Sublessor"), and PlaceWare, Inc., a Delaware corporation ("Sublessee").
Sublessor and Sublessee hereby agree as follows:

     1.  Recitals: This Sublease is made with reference to the fact that the
         --------
Vanni Business Park General Partnership, as landlord ("Master Lessor"), and
Sublessor, as tenant, entered into that certain lease, dated as of August 28,
1992 (the "Lease"), which Lease incorporated certain of the terms of that
certain Lease Agreement dated February 20, 1986 between Master Lessor and
Equatorial Communications Company (the "Master Lease Terms"), and which Lease
was amended by a First Amendment to Vanni Business Park Industrial Lease dated
May 5, 1994, a Second Amendment to Vanni Business Park Industrial Lease dated
August 1994 and a Third Amendment to Vanni Business Park Industrial Lease dated
May 1999 (the Lease and the Master Lease Terms, as amended, shall be
collectively referred to herein as the "Master Lease"), with respect to premises
consisting of approximately 40,000 square feet of space, located at 295 North
Bernardo Avenue, Mountain View, California (the "Premises"). A copy of the
Master Lease is attached hereto as Exhibit A.
                                   ---------

     2.  Premises: Sublessor hereby subleases to Sublessee, and Sublessee hereby
         --------
subleases from Sublessor, all of the Premises (hereinafter, the "Subleased
Premises"), as more particularly described in the Master Lease.

     3.  Term: The term (the "Term") of this Sublease shall be for the period
         ----
commencing on October 1, 1999 (the "Commencement Date") and ending on September
30, 2002 (the "Expiration Date"), unless this Sublease is sooner terminated
pursuant to its terms or the Master Lease is sooner terminated pursuant to its
terms. If Sublessor permits Sublessee to occupy the Subleased Premises prior to
the Commencement Date, such occupancy (i) shall be subject to all of the
provisions of this Sublease, except for the obligation to pay Base Rent (as
defined below); and (ii) shall not advance the Expiration Date of this Sublease.

     4.  Rent:
         ----

         A.  Base Rent. Sublessee shall pay to Sublessor as base rent for the
             ---------
Subleased Premises for each month during the Term the following amounts per
month ("Base Rent"): (i) from the first (1st) through the twelfth (12th) months,
Ninety-Four Thousand Dollars ($94,000); (ii) from the thirteenth (13th) through
the twenty-fourth (24th) months, Ninety-Six Thousand Dollars ($96,000); and
(iii) from the twenty-fifth (25th) through the thirty-sixth (36th) months,
Ninety-Eight Thousand Dollars ($98,000). Base Rent and Additional Rent, as
defined in Section 4.B below, shall be paid on or before the first (1st) day of
each month. Base Rent and Additional Rent for any period during the Term hereof
which is for less than one (1) month of the Term shall be a pro rata portion of
the monthly installment based on a thirty (30) day month. Base Rent and
Additional Rent shall be payable without notice or demand and without any
deduction, offset, or abatement, in lawful money of the United States of
America. Base Rent and Additional Rent shall be paid directly to Sublessor at
510 DeGuigne Drive, Sunnyvale, California 94086, Attention: Chief Financial
Officer, or such other address as may be designated in writing by Sublessor.

         B.  Additional Rent. All monies other than Base Rent required to be
             ---------------
paid by Sublessee under this Sublease, including, without limitation, all
impositions, insurance premiums, operating costs, taxes, common area charges and
other amounts payable under Sections 4.03 and 7.02 and Articles 8 and 10 of the
Master Lease Terms shall be deemed additional rent ("Additional Rent"). Base
Rent and Additional
<PAGE>

Rent hereinafter collectively shall be referred to as "Rent". Sublessee and
Sublessor agree, as a material part of the consideration given by Sublessee to
Sublessor for this Sublease, that Sublessee shall pay all costs, expenses,
taxes, insurance, maintenance and other charges of every kind and nature arising
in connection with this Sublease, the Master Lease or the Subleased Premises,
except for rent due under the Master Lease or Master Lessor's obligations, such
that Sublessor shall receive, as a net consideration for this Sublease, the Base
Rent payable under Section 4.A. hereof.

         C.  Payment of First Month's Rent. Sublessor recognizes receipt of the
             -----------------------------
sum of Ninety-Four Thousand Dollars ($94,000), which shall constitute Base Rent
for the first month of the Term.

     5.  Security Deposit:
         ----------------

         A.  Upon execution hereof, Sublessee shall deposit with Sublessor the
sum of Two Hundred Ninety-Four Thousand Dollars ($294,000) (the "Security
Deposit"), in cash, as security for the performance by Sublessee of the terms
and conditions of this Sublease. If Sublessee fails to pay Rent or other charges
due hereunder or otherwise defaults with respect to any provision of this
Sublease, then Sublessor may draw upon, use, apply or retain all or any portion
of the Security Deposit for the payment of any Rent or other charge in default,
for the payment of any other sum which Sublessor has become obligated to pay by
reason of Sublessee's default, or to compensate Sublessor for any loss or damage
which Sublessor has suffered thereby. If Sublessor so uses or applies all or any
portion of the Security Deposit, then Sublessee, upon demand therefor, shall
deposit cash with Sublessor in the amount required to restore the Security
Deposit to the full amount stated above. Upon the expiration of this Sublease,
if Sublessee is not in default, Sublessor shall return to Sublessee so much of
the Security Deposit as has not been applied by Sublessor pursuant to this
paragraph, or which is not otherwise required to cure Sublessee's defaults.

         B.  Sublessee shall have the right to provide a portion of the Security
Deposit in the amount of One Hundred Ninety-Six Thousand Dollars ($196,000) in
the form of a letter of credit (the "Letter of Credit"). The Letter of Credit
shall be in a form and issued by a financial institution that is reasonably
acceptable to Sublessor. Sublessee shall cause the Letter of Credit to remain in
effect during the entire Sublease Term and for an additional sixty (60) days
following the expiration or earlier termination of this Sublease, and shall
extend or renew the Letter of Credit from time to time at least thirty (30) days
before its stated expiration date. If Sublessee fails to maintain, renew or
replace the Letter of Credit at least thirty (30) days before its stated
expiration date, Sublessor may, without prejudice to any other right or remedy,
draw upon the entire amount of the Letter of Credit. Any amount drawn by
Sublessor on the Letter of Credit but not applied by Sublessor to satisfy
Sublessee's obligations hereunder shall be held by Sublessor in accordance with
the other provisions of this section. If Sublessor draws on any portion of the
Letter of Credit, Sublessee shall, within three (3) days of demand by Sublessor,
deposit immediately available funds with Sublessor in the full amount of the
Security Deposit.

     6.  Holdover: In the event that Sublessee does not surrender the Subleased
         --------
Premises by the Expiration Date in accordance the terms of this Sublease,
Sublessee shall indemnify, defend, protect and hold harmless Sublessor from and
against all loss and liability resulting from Sublessee's delay in surrendering
the Subleased Premises and pay Sublessor holdover rent equal to one and one-half
times the Rent payable under this Sublease during the last month of the Term.

     7.  Repairs: Sublessor shall deliver the Subleased Premises to Sublessee
         -------
with the exterior walls, roof, interior structure, mechanical equipment,
heating, ventilating and air conditioning systems, fire and life safety systems
and plumbing and electrical distribution in the Subleased Premises in good
working order. Sublessee's failure to make an objection with respect to any
aspect of the foregoing within ninety (90) days of the Commencement Date shall
be deemed a conclusive presumption that Sublessor has complied with its

                                      -2-
<PAGE>

requirements with respect to such aspects. The parties acknowledge and agree
that Sublessee is subleasing the Subleased Premises on an "as is" basis, and
that Sublessor has made no representations or warranties with respect to the
condition of the Subleased Premises as of the Commencement Date except as set
forth in this paragraph. Sublessor shall have no obligation whatsoever to make
or, except as expressly set forth in Section 23 hereof, pay the cost of any
alterations, improvements or repairs to the Subleased Premises, including,
without limitation, any improvement or repair required to comply with any law,
regulation, building code or ordinance (including the Americans with
Disabilities Act of 1990). Sublessee shall look solely to Master Lessor for
performance of any repairs required to be performed by Master Lessor under the
terms of the Master Lease.

     8.  Right to Cure Defaults: If Sublessee fails to pay any sum of money to
         ----------------------
Sublessor, or fails to perform any other act on its part to be performed
hereunder, then Sublessor may, but shall not be obligated to, after passage of
any applicable notice and cure periods, make such payment or perform such act.
All such sums paid, and all reasonable costs and expenses of performing any such
act, shall be deemed Additional Rent payable by Sublessee to Sublessor upon
demand, together with interest thereon at the Interest Rate from the date of the
expenditure until repaid.

     9.  Assignment and Subletting. Sublessee may not assign this Sublease,
         -------------------------
sublet the Subleased Premises, transfer any interest of Sublessee therein or
permit any use of the Subleased Premises by another party (collectively,
"Transfer"), without the prior written consent of Sublessor (not to be
unreasonably withheld) and Master Lessor and without complying with the terms of
Article 12 of the Master Lease Terms, as incorporated herein. Sublessor shall
provide such consent or denial within ten (10) business days of a request for
consent, provided such consent includes all information reasonably required by
Sublessor to respond to such request. If Sublessee receives rent or other
consideration for any Transfer in excess of the Rent payable under this
Sublease, or in the case of a sublease of a portion of the Subleased Premises,
in excess of the Rent that is fairly allocable to such portion, Sublessee shall
pay Sublessor seventy-five percent (75%) of the difference between each such
payment of Rent or other consideration and the Rent required hereunder, after
recovering Sublessee's actual, reasonable costs of subleasing, including
attorneys' fees, commissions and alterations (to the extent Sublessor is
permitted to deduct such costs before paying any "profit" to Master Lessor).
Notwithstanding anything to the contrary herein, in the event that Sublessee
requests consent to a Transfer which would result in more than sixty percent
(60%) of the-Subleased Premises being Transferred, Sublessor shall have the
right, by giving notice to Sublessee within thirty (30) days after receipt of
any request by Sublessee to consent to a Transfer, to recapture the portion of
the Subleased Premises to be Transferred (the "Subject Space"). Such recapture
notice shall cancel and terminate this Sublease with respect to the Subject
Space as of the date of Sublessor's proposed Transfer. If this Sublease is
canceled with respect to less than the entire Subleased Premises, the Rent
hereunder shall be prorated on the basis of the number of square feet retained
by Sublessee in proportion to the number of rental square feet in the Subleased
Premises, and this Sublease, as so amended, shall continue thereafter in full
force and effect. Upon request by either party, the parties shall execute
written confirmation of the same, including any additional changes required as a
result of the Premises becoming a multi-tenant site, if applicable.

     10. Use: Sublessee may use the Subleased Premises only for the uses
         ---
identified in Section 6.01 of the Master Lease Terms. Sublessee shall not use,
store, transport or dispose of any hazardous material in or about the Subleased
Premises. Without limiting the generality of the foregoing, Sublessee, at its
sole cost, shall comply with all laws relating to hazardous materials. Sublessee
shall indemnify, defend with counsel reasonably acceptable to Sublessor and hold
Sublessor harmless from and against all claims, losses, costs, damages,
liabilities and expenses of every type and nature, to the extent caused by the
release, disposal, discharge or emission of hazardous materials on or about the
Subleased Premises by Sublessee or its agents, contractors, invitees or
employees. "Hazardous materials" shall mean any material or substance that is
now

                                      -3-
<PAGE>

or hereafter prohibited or regulated by any statute, law, rule, regulation or
ordinance or that is now or hereafter designated by any governmental authority
to be radioactive, toxic, hazardous or otherwise a danger to health,
reproduction or the environment.

     11.  Effect of Conveyance: As used in this Sublease, the term "Sublessor"
          --------------------
means the holder of the tenant's interest under the Master Lease. In the event
of any assignment, transfer or termination of the tenant's interest under the
Master Lease, which assignment, transfer or termination may occur at any time
during the Term hereof in Sublessor's sole discretion, Sublessor shall be and
hereby is entirely relieved of all covenants and obligations of Sublessor
hereunder, and it shall be deemed and construed, without further agreement
between the parties, that any transferee has assumed and shall carry out all
covenants and obligations thereafter to be performed by Sublessor hereunder.
Sublessor may transfer and deliver any security of Sublessee to the transferee
of the tenant's interest under the Master Lease, and thereupon Sublessor shall
be discharged from any further liability with respect thereto.

     12.  Delivery and Acceptance: If Sublessor fails to deliver possession of
          -----------------------
the Subleased Premises to Sublessee on or before the date set forth in Section 3
hereof for any reason whatsoever, then this Sublease shall not be void or
voidable, nor shall Sublessor be liable to Sublessee for any loss or damage;
provided, however, that in such event, Rent shall abate until Sublessor delivers
possession of the Subleased Premises to Sublessee.

     13.  Improvements: No alteration or improvements shall be made to the
          ------------
Subleased Premises, except in accordance with the Master Lease, and with the
prior written consent of both Master Lessor and Sublessor, which shall not be
unreasonably withheld or delayed. Sublessee shall have no obligation to remove
alterations or improvements made to the Subleased Premises by Sublessor.

     14.  Release and Waiver of Subrogation: Sublessor and Sublessee hereby
          ---------------------------------
release each other from any damage to property or loss of any kind which is
caused by or results from any risk insured against under any property insurance
policy required to be carried by either party under this Sublease.

     15.  Insurance: Sublessee shall obtain and keep in full force and effect,
          ---------
at Sublessee's sole cost and expense, during the Term the insurance required of
the tenant under Article 8 of the Master Lease Terms. All such liability
insurance policies shall name Master Lessor, Sublessor and any additional
parties required by Master Lessor or Sublessor as additional insureds.

     16.  Default: Sublessee shall be in material default of its obligations
          -------
under this Sublease if any of the following events occur:

          A.  Sublessee fails to pay any Rent when due, when such failure
continues for two (2) days after written notice from Sublessor to Sublessee that
any such sum is due; or

          B.  Sublessee fails to perform any term, covenant or condition of this
Sublease (except those requiring payment of Rent) and fails to cure such breach
within ten (10) days after delivery of a written notice specifying the nature of
the breach; provided, however, that if more than ten (10) days reasonably are
required to remedy the failure, then Sublessee shall not be in default if
Sublessee commences the cure within the ten (10) day period and thereafter
completes the cure within sixty (60) days after the date of the notice; or

          C.  Sublessee commits any other act or omission which constitutes a
default under the Master Lease, which has not been cured after delivery of
written notice and passage of the applicable grace period provided in the Master
Lease as modified, if at all, by the provisions of this Sublease.

                                      -4-
<PAGE>

     17.  Remedies: In the event of any default by Sublessee, Sublessor shall
          --------
have all remedies provided pursuant to Section 13.02 of the Master Lease Terms
and by applicable law.

     18.  Broker: Sublessor and Sublessee each represent to the other that they
          ------
have dealt with no real estate brokers, finders, agents or salesmen other than
Donald H. Reimann and Michael S. Rosendin of Colliers International,
representing Sublessor, and Jack C. Spallino and Scott Lagan of Spallino Reid
Corporate Real Estate Services, representing Sublessee, in connection with this
transaction. Each party agrees to hold the other party harmless from and against
all claims for brokerage commissions, finder's fees or other compensation made
by any other agent, broker, salesman or finder as a consequence of said party's
actions or dealings with such agent, broker, salesman, or finder.

     19.  Notices: Unless at least five (5) days' prior written notice is given
          -------
in the manner set forth in this paragraph, the address of each party for all
purposes connected with this Sublease shall be that address set forth below
their signatures at the end of this Sublease. All notices, demands or
communications in connection with this Sublease shall be (a) personally
delivered; or (b) properly addressed and (i) submitted to an overnight courier
service, charges prepaid, or (ii) deposited in the mail (registered or
certified, return receipt requested, and postage prepaid). Notices shall be
deemed delivered upon receipt, if personally delivered, one (1) business day
after being submitted to an overnight courier service and three (3) business
days after mailing, if mailed as set forth above. All notices given to Master
Lessor under the Master Lease shall be considered received only when delivered
in accordance with the Master Lease.

     20.  Other Sublease Terms:
          --------------------

          A.  Incorporation By Reference. Except as set forth below, the terms
              --------------------------
and conditions of this Sublease shall include all of the terms of the Master
Lease and such terms are incorporated into this Sublease as if fully set forth
herein, except that: (i) each reference in such incorporated sections to "Lease"
shall be deemed a reference to "Sublease"; (ii) each reference to the "Premises"
shall be deemed a reference to the "Subleased Premises"; (iii) each reference to
"Lessor" and "Lessee" shall be deemed a reference to "Sublessor" and
"Sublessee", respectively, except as otherwise expressly set forth herein; (iv)
with respect to work, services, repairs, restoration, insurance, indemnities,
representations, warranties or the performance of any other obligation of Master
Lessor under the Master Lease, the sole obligation of Sublessor shall be to
request the same in writing from Master Lessor as and when requested to do so by
Sublessee, and to use Sublessor's reasonable efforts (without requiring
Sublessor to spend more than a nominal sum) to obtain Master Lessor's
performance; (v) with respect to any obligation of Sublessee to be performed
under this Sublease, wherever the Master Lease grants to Sublessor a specified
number of days to perform its obligations under the Master Lease, except as
otherwise provided herein, Sublessee shall have three (3) fewer days to perform
the obligation, including, without limitation, curing any defaults; (vi) with
respect to any approval required to be obtained from the "Lessor" under the
Master Lease, such consent must be obtained from both Master Lessor and
Sublessor, and the approval of Sublessor may be withheld if Master Lessor's
consent is not obtained; (vii) in any case where the "Lessor" reserves or is
granted the right to manage, supervise, control, repair, alter, regulate the use
of, enter or use the Premises or any areas beneath, above or adjacent thereto,
such reservation or grant of right of entry shall be deemed to be for the
benefit of both Master Lessor and Sublessor; (viii) in any case where "Lessee"
is to indemnify, release or waive claims against "Lessor", such indemnity,
release or waiver shall be deemed to run from Sublessee to both Lessor and
Sublessor; (ix) in any case where "Lessee" is to execute and deliver certain
documents or notices to "Lessor", such obligation shall be deemed to run from
Sublessee to both Master Lessor and Sublessor; (x) in any case where "Lessee" is
to make a payment to "Lessor", such amounts shall be paid to Sublessor; (xi) the
reference to "Section 4.01" in Section 4.03 of the Master Lease Terms shall mean
Section 4 of this Sublease; (xii) the reference to "16.19" in Section 10.03 of
the Master Lease Terms shall be to "16.44"; (xiii) Sublessee shall have the
right to Transfer the Subleased Premises as described in Section 12.02 of the
Master Lease

                                      -5-
<PAGE>

Terms only after providing Sublessor with thirty (30) days prior written notice
and obtaining the prior written consent of Master Lessor, if applicable; (xiv)
the reference in Section 12.04 to "$350" shall be to "$1,000" as to Sublessor
only; (xv) the reference to the square footage of the Premises in Article 43 of
the Master Lease Terms shall be to "40,000"; and (xiv) the provisions of Section
9.05 shall apply only during the last year of the Option term.

     Notwithstanding the provisions of subpart (iii) above, (a) the following
provisions of the Master Lease shall not be incorporated herein: Articles 1-3,
Sections 4.01, 4.02 and 4.03 (the last sentence of the first paragraph only),
Article 5, Sections 6.02(a), 6.02(b) (the first line only), 6.03(a) and (b),
7.04 and 13.03 (the last sentence only) and Articles 23, 25, 36 (the second
sentence only), 37, 38 (the last sentence only), 41 and 42 of the Master Lease
Terms, the Lease (except Section F), the First Amendment, the Second Amendment
(except Section 4) and the Third Amendment; (b) references in the following
provisions to "Lessor" shall mean Master Lessor only: Sections 7.01 (the first
reference only), 7.02, 8.01 (the first paragraph only), 8.03, 9.01, 9.02, 10.01
(the second paragraph only), 10.04 (except the reference in the second line of
subpart (c)) and 14.02 and Article 38 of the Master Lease Terms; (c) references
in the following provisions to "Lessor" shall mean Master Lessor and Sublessor:
Sections 8.04 and 12.04 of the Master Lease Terms; and (d) references in the
following provisions to "Lessor" shall mean Master Lessor or Sublessor: Sections
7.01, 10.02 and 10.04(c) (the reference in the second line) and Article 30 of
the Master Lease Terms.

          B.  Assumption of Obligations. This Sublease is and at all times shall
              -------------------------
be subject and subordinate to the Master Lease and the rights of Master Lessor
thereunder. Sublessee hereby expressly assumes and agrees: (i) to comply with
all provisions of the Master Lease which are incorporated hereunder; and (ii) to
perform all the obligations on the part of the "Lessee" to be performed under
the terms of the Master Lease during the term of this Sublease which are
incorporated hereunder. In the event of a conflict between the provisions of
this Sublease and the Master Lease, as between Sublessor and Sublessee, the
provisions of this Sublease shall control.

     21.  Conditions Precedent: This Sublease and Sublessor's and Sublessee's
          --------------------
obligations hereunder are conditioned upon the written consent of Master Lessor.
If Sublessor fails to obtain Master Lessor's consent within thirty (30) days
after execution of this Sublease by Sublessor, then Sublessor or Sublessee may
terminate this Sublease by giving the other party written notice thereof at any
time before receipt of Master Lessor's consent, and Sublessor shall return to
Sublessee the Security Deposit and the first month's rent paid hereunder.

     22.  Authority to Execute: Sublessee and Sublessor each represent and
          --------------------
warrant to the other that each person executing this Sublease on behalf of each
party is duly authorized to execute and deliver this Sublease on behalf of that
party.

     23.  Carpeting Allowance: Sublessor shall reimburse Sublessee the actual
          -------------------
and reasonable costs that Sublessee incurs to install new carpeting within the
Subleased Premises (the "Recarpeting"), up to and not to exceed an amount equal
to One Hundred Twenty Thousand Dollars ($120,000) (the "Cap"). Upon Sublessee's
lien free completion of the Recarpeting, Sublessee shall present to Sublessor
paid invoices, unconditional lien waivers and other items reasonably required by
Sublessor to evidence Sublessee's completion of and payment for the Recarpeting.
Within ten (10) days of Sublessor's receipt of all such items, Sublessor shall
reimburse Sublessee its actual, reasonable costs to perform the Recarpeting, not
to exceed the amount of the Cap. Sublessor's obligations under this section
shall terminate upon the first anniversary of the Commencement Date. Sublessee
shall perform the Recarpeting in a good and workmanlike manner, in compliance
with all laws and otherwise in compliance with the terms of the Master Lease.

                                      -6-
<PAGE>

     24.  Extension:
          ---------

          A.  Provided that a default has not occurred hereunder, Sublessee
shall have one option (the "Option") to extend the term of this Sublease for an
additional term of forty-two (42) months, commencing when the initial term
expires and terminating March 31, 2006, upon the terms and conditions set forth
in this section. Sublessee may exercise such option by giving Sublessor written
notice of its intention not less than nine (9) months nor more than twelve (12)
months prior to the expiration of the initial term of this Sublease. The Option
is personal to PlaceWare, Inc. or a corporate affiliate of PlaceWare, Inc., and
may be not exercised following an assignment of this Sublease or a sublease of
all or any portion of the Subleased Premises.

          B.  If the Option is exercised, the base rent for the Subleased
Premises shall become the greater of Ninety-Eight Thousand Dollars ($98,000) per
month and the then current fair market monthly rent ("FMR") for the Subleased
Premises as of the commencement date of the extended term, and shall be subject
to rent escalations, if appropriate, as determined by the agreement of the
parties or, if the parties cannot agree within sixty (60) days prior to the
commencement of the extended term, then by an appraisal. All other terms and
conditions contained in this Sublease shall remain in full force and effect and
shall apply during the Option term. If it becomes necessary to determine the FMR
by appraisal, real estate appraiser(s), all of whom shall be Members of the
Appraisal Institute and shall have at least five (5) years experience appraising
comparable space located in the vicinity of the Subleased Premises, shall be
appointed and shall act in accordance with the following procedures:

              (i)  If the parties are unable to agree on the FMR within the
allowed time, either party may demand an appraisal by giving written notice to
the other party, which demand to be effective must state the name, address and
qualifications of an appraiser selected by the party demanding an appraisal (the
"Notifying Party"). Within ten (10) days following the Notifying Party's
appraisal demand, the other party (the "Non-Notifying Party") shall either
approve the appraiser selected by the Notifying Party or select a second
properly qualified appraiser by giving written notice of the name, address and
qualification of such appraiser to the Notifying Party. If the Non-Notifying
Party fails to select an appraiser within the ten (10) day period, the appraiser
selected by the Notifying Party shall be deemed selected by both parties and no
other appraiser shall be selected. If two appraisers are selected, they shall
select a third appropriately qualified appraiser. If the two appraisers fail to
select a third qualified appraiser, the third appraiser shall be appointed by
the then presiding judge of the county where the Subleased Premises are located
upon application by either party.

              (ii) If only one appraiser is selected, that appraiser shall
notify the parties in simple letter form of its determination of the FMR within
fifteen (15) days following his selection, which appraisal shall be conclusively
determinative and binding on the parties as the appraised FMR. If multiple
appraisers are selected, the appraisers shall meet not later than ten (10) days
following the selection of the last appraiser. At such meeting the appraisers
shall attempt to determine the FMR as of the commencement date of the extended
term by the agreement of at least two (2) of the appraisers. If two (2) or more
of the appraisers agree on the FMR at the initial meeting, such agreement shall
be determinative and binding upon the parties hereto and the agreeing appraisers
shall, in simple letter form executed by the agreeing appraisers, forthwith
notify both Sublessor and Sublessee of the amount set by such agreement. If
multiple appraisers are selected and two (2) appraisers are unable to agree on
the FMR, all appraisers shall submit to Sublessor and Sublessee an independent
appraisal of the FMR in simple letter form within twenty (20) days following
appointment of the final appraiser. The parties shall then determine the FMR by
averaging the appraisals; provided that any high or low appraisal, differing
from the middle appraisal by more than ten percent (10%) of the middle
appraisal, shall be disregarded in calculating the average.

                                      -7-
<PAGE>

          (iii)  If only one appraiser is selected, then each party shall pay
one-half of the fees and expenses of that appraiser. If three appraisers are
selected, each party shall bear the fees and expenses of the appraiser it
selects and one-half of the fees and expenses of the third appraiser.

     25.  Hazardous Materials: To Sublessor's actual knowledge, Sublessor has
          -------------------
not released, discharged or emitted hazardous materials on or about the
Subleased Premises in violation of applicable laws.

     IN WITNESS WHEREOF, the parties have executed this Sublease as of the day
and year first above written.



SUBLESSEE:                               SUBLESSOR:


PROXIM, INC.,                            PLACEWARE, INC.,
a Delaware corporation.                  a Delaware corporation

By:    /s/ Keith E. Glover               By:    /s/ XXX
      ------------------------------           -----------------------------
Name:  Keith E. Glover                   Name:  XXX
      ------------------------------           -----------------------------
Its:   V.P. & C.F.O.                     Its:   CFO
      ------------------------------           -----------------------------

Address: 510 DeGuigne Drive              Address:  201 Ravendale Drive
         Sunnyvale, California 94086               Mountain View, CA 94043
         Attn.: Chief Financial Officer            Attn: Chief Financial Officer

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<PAGE>

                              CONSENT TO SUBLEASE

The undersigned ("Lessor") hereby consents to the sublease by PROXIM, INC.,
("Sublessor"), a Delaware corporation to PLACEWARE, INC., ("Sublessee"), a
Delaware corporation, of the entire premises leased by Sublessor as Lessee under
that certain Lease between Lessor and Proxim, Inc., which Lease is dated August
28, 1992, (the "Lease"), which Lease incorporated certain of the terms of that
certain Lease Agreement dated February 20, 1986 between Master Lessor and
Equatorial Communications Company, and which Lease was amended by a First
Amendment to Vanni Business Park Industrial Lease dated May 5, 1994, a Second
Amendment to Vanni Business Park Industrial Lease dated August 1994 and a Third
Amendment to Vanni Business Park Industrial Lease (the "Third Amendment") dated
May 1999, respecting (the "Premises") commonly known as 295 Noah Bernardo
Avenue, Building "C", Mountain View, California, subject to the following:

1. Such sublease shall be effectuated pursuant to the form of Sublease prepared
by Sublessor and delivered by Sublessor to Lessor, a copy of which is attached
hereto as Exhibit A. Such document, when executed by both Sublessor and
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Sublessee, shall be deemed the "Sublease" for all purposes under the this
Consent.

2. Sublessor shall pay to Lessor its attorneys fees incurred in connection with
this sublease in the amount of $350.00 pursuant to section 12.04 of the Lease.

3. Sublessor shall pay to Lessor with its regularly scheduled rent payments
(50%) of all sums collected by Sublessor from Sublessee or assignee which are in
excess of the rent owing by Sublessor to Lessor pursuant to provisions of the
Lease and each Amendment thereto after first deducting the cost of (i) broker's
commission paid by Sublessor with regard to the sublease; (ii) reasonable legal
fees related directly to the sublease paid by Sublessor; (iii) the cost of
improvements made to the subleased premises by Sublessor at Sublessor's expense
for the sole purpose of subletting.

4. Sublessor shall effectuate the Third Amendment to Vanni Business Park
Industrial Lease by paying to Lessor the increased security deposit pursuant to
paragraph 3 of the Third Amendment. The Third Amendment shall not be effective
and Lessor's Consent to Sublease deemed null and void at Lessors' option should
Sublessor not pay to Lessor the increased deposit pursuant to paragraph 3 of the
Third Amendment.

5. In accordance with Section 12.03 of the Lease, this Consent does not relieve
Sublessor of any liability as Lessee under the Lease.

6. This Consent shall not be construed to be a consent to any subsequent
sublease, extension of sublease, assignment, mortgage, or other transfer of all
or any portion of the Premises or of all or any interest in the Lease.

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<PAGE>

7. Notwithstanding anything to the contrary contained in the Sublease, nothing
in this Consent shall be deemed to be or construed as an agreement be Lessor to
amend or otherwise modify any of the terms of the Lease. In the event of any
inconsistencies between the provisions of the Sublease and the Provisions of the
Lease, the provisions of the Lease control.

8. Without limiting the generality of paragraphs 6 & 7 above, any subsequent
sublease, extension of sublease, assignment, mortgage or other transfer of all
or any portion of the Premises or of any interest under the Lease shall be
subject to Lessor's consent as provided for in Section 12 of the Lease. Such
consent is further subject to approval and rejection rights that Lessor's lender
may currently have or accrue in the future.

                                   LESSOR

                                   Vanni Business Park LLC,
                                   a Delaware limited liability company


                                   By   /s/ David V. Vanni
                                      ----------------------------
                                      David V. Vanni, Member

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