Document:

<PAGE>

                                                                   EXHIBIT 10.15

[***]=Certain information in this Exhibit has been omitted and filed separately
with the Securities and Exchange Commission.

                                LEASE AGREEMENT

                                    between

                        NEXCOMM ASSET ACQUISITION I, LP,

                                  as Landlord,

                                      and

                                 EQUINIX, INC.,

                                   as Tenant

                                    Infomart
                           The Technology Community

                                      [*]
                              Dallas, Texas 75207
                                  214-800-8000

*CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       1
<PAGE>

                       INFOMART The Technology Community
                         is a registered servicemark of
                            IFM Services, LLC, [*],
                        Suite 6038, Dallas, Texas 75207

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       2
<PAGE>

                                LEASE AGREEMENT
                                    INFOMART
                          THE  TECHNOLOGY  COMMUNITY

THIS LEASE AGREEMENT ("Lease") is made and entered into as of the 21st day of
January, 2000, by and between NEXCOMM ASSET ACQUISITION I, LP, a Texas limited
partnership ("Landlord"), whose address is 1950 Stemmons Freeway, Dallas, Texas
75207 and EQUINIX, INC., a Delaware corporation ("Tenant"), whose address is 901
Marshall Street, Redwood City, California 94063, Attention:  Keith Taylor.

                                   ARTICLE 1

                   BASIC LEASE INFORMATION AND DEFINED TERMS

          Section 1.1.   Basic Lease Information.

                  (a)    Base Rent shall mean the following:
                         ---------
                         From the Commencement Date until the Rental
                         Commencement Date, Base Rent shall be [*] Dollars
                         ($[*]),

                         From the Rental Commencement Date through May 31, 2002,
                         Base Rent shall be [*] Dollars ($[*]) per month,

                         From the June 1, 2002 through May 31, 2004, Base Rent
                         shall be [*] Dollars ($[*]) per month,

                         From the June 1, 2004 through May 31, 2006, Base Rent
                         shall be [*] Dollars ($[*]) per month,

                         From the June 1, 2006 through May 31, 2008, Base Rent
                         shall be [*] Dollars ($[*]) per month,

                         From the June 1, 2008 through May 31, 2010, Base Rent
                         shall be [*] Dollars ($[*]) per month.

                  (b)    Base Year shall mean 2000.
                         ---------

                  (c)    Building shall mean the office building and information
                         --------
processing center located on the Land.

                  (d)    Building Rules shall mean all rules and regulations
                         --------------
adopted or modified by Landlord from time to time for the safety, care,
cleanliness, and reputation of the Building and for the preservation of good
order in the Building. The current Building Rules are attached at Exhibit "C."
                                                                  ----------

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       3
<PAGE>

               (e)       Commencement Date shall mean the Effective Date. Tenant
                         -----------------
shall be deemed to commence occupancy of the Premises on the date Tenant takes
possession of the Premises for the purpose of equipping, furnishing, and
improving the Premises. "Rental Commencement Date" shall mean the earlier of [*]
months after the Effective Date or June 1, 2000. Base Rent shall be adjusted
accordingly if the Rental Commencement Date is other than June 1, 2000.

               (f)       Common Areas shall mean those areas within the Project
                         ------------
devoted to corridors, elevator foyers, restrooms, lobby areas, meeting rooms,
and other similar facilities provided for the common use or benefit of tenants
generally.

               (g)       INFOMART shall mean "INFOMART - The Technology
                         --------
Community" and shall include the Project as it currently exists or as it may
from time to time hereafter be expanded or modified.

               (h)       Insurance Costs shall mean all costs incurred by
                         ---------------
Landlord in obtaining insurance on the Project, including property, liability,
and casualty insurance on the Building, but excluding all insurance costs which
Tenant is required to provide under Section 7.3 below.

               (i)       Land shall mean the tract of real property which is
                         ----
described in Exhibit "A" to this Lease.

               (j)       Lease Term shall mean a term commencing on the Rental
                         ----------
Commencement Date and continuing for one hundred twenty (120) full calendar
months.

               (k)       Permitted Use shall mean use for the installation,
                         -------------
maintenance and operation of information processing and telecommunications
products and services, for offices, and for storage and service areas incidental
and related to such uses, and to include collocation and other
telecommunications related operations.

               (l)       Premises shall mean Suite No. 1034 in the Building, as
                         --------
outlined on the floor plan of the Building which is attached as Exhibit "B" to
                                                                ----------
this Lease.

               (m)       Project shall mean, collectively, the Building, the
                         -------
Land, and all other improvements located on the Land (including parking areas,
parking garages, plaza areas, and other similar areas relating to the Building).

               (n)       Rent shall mean, collectively, the Base Rent; Tenant's
                         ----
Proportionate Share of Insurance Costs, Utility Costs and Taxes; and any other
amounts payable to Landlord by Tenant.

               (o)       Rentable Square Feet shall mean the Usable Square Feet
                         --------------------
within the Premises, together with an additional amount representing a portion
of the Common Areas, Service Areas and other non-tenant space on floors one (1)
through six (6) in the Building. For purposes of this Lease, the parties have
agreed that the Premises shall be deemed to consist of [*] Rentable Square Feet
and floors one (1) through six (6) of the Building shall be deemed to consist of
[*] Rentable Square Feet. However, both Landlord and Tenant acknowledge that

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       4
<PAGE>

neither of these figures was calculated by measuring the Common Areas, Service
Areas and other non-tenant spaces in the Building and that neither Landlord nor
Tenant shall have a right to demand remeasurement or recalculation of the
Rentable Square Feet applicable to the Premises or the Building.

               (p)       Security Deposit shall mean [*] Dollars ($[*]).
                         ----------------

               (q)       Service Areas shall mean those areas within the outside
                         -------------
walls of the Building which are used for mechanical rooms, stairs, elevator
shafts, flues, vents, stacks, pipe shafts, risers, raceways, and vertical
penetrations (but shall not include any such areas for the exclusive use of a
particular tenant).

               (r)       Taxes shall mean all taxes and assessments and
                         -----
governmental charges, whether federal, state, county or municipal, and whether
levied or assessed by taxing districts or authorities presently taxing the
Premises or the Project or any part of either, or by others, subsequently
created or otherwise, and any other taxes and assessments attributable to the
Project or its operation together with any costs incurred by Landlord (including
attorneys' fees and costs of investigation) relative to any negotiation,
contest, or appeal pursued by Landlord to reduce or prevent an increase in any
portion of the Taxes, regardless of whether any reduction or limitation is
obtained, provided that such costs are allocated only to the periods for which
Landlord is trying to have the Taxes revised.

               (s)       Tenant's Proportionate Share shall mean a fraction, the
                         ----------------------------
numerator of which is the number of Rentable Square Feet within the Premises,
and the denominator of which is the number of Rentable Square Feet on floors two
(2) through six (6) of the Building. Accordingly, the parties acknowledge and
agree that Tenant's Proportionate Share under this Lease is [*] percent.

               (t)       Trade Fixtures shall mean any and all signs and other
                         --------------
equipment, including without limitation, the switch and related equipment to be
installed by Tenant or placed by Tenant within the Premises pursuant to the
provisions of this Lease and any and all items of property used by Tenant in the
Premises, including furniture and equipment and "Tenant Equipment" as defined in
Exhibit "D" attached hereto. However, the term Trade Fixtures shall not include
any permanent leasehold improvements (including any floor, wall, or ceiling
coverings, any interior walls or partitions, , or any property which is a part
of or associated with any electrical, plumbing, or mechanical system other than
the generator and cooling equipment to be installed by Tenant in accordance with
the provisions of Exhibit D attached hereto and those items which are designated
as being "Trade Fixtures" on the Plans and Specifications approved by both
parties pursuant to the attached Work Letter), notwithstanding that the same may
have been installed within the Premises by Tenant.

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       5
<PAGE>

               (u)       Usable Square Feet shall mean the gross number of
                         ------------------
square feet enclosed by the surface of the exterior glass walls, the midpoint of
any walls separating portions of the Premises from those of adjacent tenants,
the slab penetration line of all walls separating the Premises from Service
Areas, and the corridor side of walls separating the Premises from Common Areas.

               (v)       Utility Costs shall mean all costs incurred by Landlord
                         -------------
in providing electricity, gas, water, and sewage disposal facilities to the
Building, (including electricity used for heating, air conditioning, operation
of office machines), and other equipment used on or about the Building, and
elevator and escalator service and lighting, but excluding all such costs which
Tenant may, from time to time, be obligated to pay on a separately metered basis
under the provisions of Section 4.3.

          Section 1.2.   Defined Terms. Each of the terms defined in Section 1.1
                         -------------
will be used as defined terms in this Lease (including the Exhibits to this
Lease). In addition, other terms are defined in various sections of this Lease.
All words which are used as defined terms in this Lease are delineated with
initial capital letters and, when delineated with initial capital letters, shall
have the meaning specified in the applicable provision of this Lease in which
such term is defined.

                                   ARTICLE 2

                               OCCUPANCY AND USE

          Section 2.1.   Premises and Term. In consideration for the obligation
                         -----------------
of Tenant to pay Rent and subject to and upon the terms and conditions stated in
this Lease, Landlord leases to Tenant, and Tenant leases from Landlord, the
Premises for the Lease Term. Landlord will deliver possession of the Premises to
Tenant on the Commencement Date. If Landlord requests, Tenant shall execute a
memorandum (in a form approved by Landlord) specifying the date upon which the
Commencement Date actually occurred.

          Section 2.2.   Leasehold Improvements. The Premises shall be delivered
                         ----------------------
to Tenant in an "as is" condition, and Tenant shall install the initial
leasehold improvements in the Premises in accordance with Section 5.1 below.
Tenant has made a complete examination and inspection of the Premises and
accepts the same in its current condition, "as is" and without recourse to
Landlord. Landlord shall have no obligation to provide any leasehold
improvements to the Premises or to repair, decorate, or paint the Premises,
unless otherwise expressly set forth in this Lease. Landlord has made no
representations or warranties to Tenant with respect to the condition of the
Premises, the Building, or the Project. Tenant's occupancy of the Premises shall
be deemed an acknowledgment by Tenant that the Premises are suitable for
Tenant's intended use, and Landlord expressly disclaims any warranty that the
Premises are suitable for Tenant's intended use. Landlord does not make any
warranties, express or implied, with respect to the Premises, the Building, or
the Project. All implied warranties (including those of habitability,
merchantability, or fitness for a particular purpose) are expressly negated and
waived.

          Section 2.3.   Use. The Premises may be used only for the Permitted
                         ---
Use specified in Section 1.1(k) and for no other purposes without the prior
written consent of

                                       6
<PAGE>

Landlord. Tenant's use of the Premises shall be in compliance with the Building
Rules and with all applicable Legal Requirements and Insurance Requirements.
Tenant shall not, even if technically within the Permitted Use, use the Premises
for any purpose which is dangerous to person or property, which creates a
nuisance, which would violate the Building Rules, or which would violate any
applicable Legal Requirement or Insurance Requirement. Tenant shall comply with,
and shall cause any Tenant Related Parties to comply with, all Building Rules
and all Legal Requirements and Insurance Requirements relating to the use,
condition, or occupancy of the Premises. "Insurance Requirements" shall mean all
terms of any insurance policy obtained by Landlord or Tenant covering or
applicable to the Premises or the Project; all requirements for the issuing of
each such insurance policy; and all orders, rules, regulations, and other
requirements of the National Board of Fire Underwriters (or any other bodies
exercising any similar functions) which are applicable to or affect the
Premises, the Building, or the Project or any use or condition of the Premises,
the Building, or the Project. "Legal Requirements" shall mean all laws,
statutes, codes, acts, ordinances, orders, judgments, decrees, injunctions,
rules, regulations, permits, licenses, authorizations, and requirements of all
governmental authorities, foreseen or unforeseen, which now or at any time
hereafter may be applicable to the Premises, the Building, or the Project,
including (a) the Americans with Disabilities Act, (b) all federal, state, and
local laws, regulations, and ordinances pertaining to air and water quality,
hazardous materials, waste disposal, and other environmental matters; and (c)
all laws, codes, and regulations pertaining to zoning, land use, health, or
safety. "Tenant Related Parties" shall mean Tenant's officers, partners,
employees, agents, contractors, licensees, concessionaires, subtenants,
customers, and invitees. In addition, the number of persons in the Premises
shall not exceed a ratio of three (3) persons per one thousand (1,000) Rentable
Square Feet within Premises ("Density Limit"). Notwithstanding the foregoing to
the contrary, Tenant shall not be responsible for (a) making any alterations to
the Premises, except to the extent such alterations are required due to Tenant's
particular use of the Premises or alterations to the Premises made by Tenant, or
(b) any remediation of hazardous materials which exist in the Premises prior to
the execution date of this Lease. Notwithstanding anything in this Lease to the
contrary, Landlord shall have the right to inspect the Density Limit within the
Premises upon forty-eight (48) hour prior written notice to Tenant. Tenant shall
have the right to accompany Landlord during any such inspection. In the event
Tenant fails to comply with the Density Limit two (2) times within a twelve (12)
month period within the Lease Term, such second (2nd) failure may, at Landlord's
sole election, constitute an event of default under this Lease; and Landlord
shall then have the right to exercise any of the remedies set forth in Section
8.2 of this Lease as a result of that default.

          Section 2.4.   Atrium Space.  Intentionally deleted.
                         ------------

          Section 2.5.   Peaceful Enjoyment. Tenant may peacefully occupy the
                         ------------------
Premises for the Permitted Use during the Lease Term subject to the terms and
provisions of this Lease and provided that Tenant pays the Rent and performs all
of Tenant's covenants and agreements contained in this Lease.

                                       7
<PAGE>

                                   ARTICLE 3

                                     RENT

          Section 3.1.   Rental Payments. Tenant shall pay Rent to Landlord for
                         ---------------
each month during the Lease Term as provided in this Lease. Rent shall be due
and payable in advance on the first (1st) day of each month during the Lease
Term. If the Commencement Date is a date other than the first (1st) day of a
calendar month, the Rent for the portion of the calendar month in which the
Commencement Date occurs shall be due and payable on the Commencement Date; and
the Rent for such partial month shall be prorated based upon the number of days
from the Commencement Date to the end of that calendar month. Rent for any
partial month at the end of the Lease Term shall be prorated based upon the
number of days from the beginning of that month to the end of the Lease Term.
Rent shall be payable at the address for Landlord designated in the first (1st)
paragraph of this Lease (or at such other address as may be designated by
Landlord from time to time). Tenant shall pay all Rent under this Lease at the
times and in the manner provided in this Lease, without abatement, notice,
demand, counterclaim, or set-off except as otherwise provided for in this
Lease.. Any charges or other sums payable by Tenant to Landlord under the terms
of this Lease shall be considered as additional Rent. No payment by Tenant or
receipt by Landlord of a lesser amount than the total amount of Rent then due
shall be deemed to be other than on account of the earliest past due installment
of Rent required to be paid under this Lease. No endorsement or statement on any
check or in any letter accompanying any check or payment of Rent shall ever be
deemed an accord and satisfaction, and Landlord may accept such check or payment
without prejudice to Landlord's right to recover the balance of the Rent then
due or to pursue any other remedy available under this Lease, at law, or in
equity.

          Section 3.2.   Interest/Late Charge. In the event that Tenant fails to
                         --------------------
pay any monthly Rent installment within five (5) days after the date on which
any such Rent installment becomes due and payable, then Tenant shall also be
obligated to pay interest on such past due amounts at a rate equal to the lesser
of eighteen percent (18%) per annum or the highest rate of interest permitted by
applicable law. Should Tenant make a partial payment of past due amounts, the
amount of such partial payment shall be applied first to reduce all accrued and
unpaid interest and late charges, in inverse order of their maturity, and then
to reduce all other past due amounts, in the inverse order of their maturity.
Tenant's failure to pay any installment of Rent when due may cause Landlord to
incur anticipated costs (including processing and accounting costs), and the
exact amount of these costs is extremely difficult to ascertain. Therefore, the
late charges permitted under this Section 3.2 shall be liquidated damages for
those costs and shall be in addition to and shall be cumulative of any other
rights and remedies which Landlord may have under this Lease with regard to the
failure of Tenant to make any payment of Rent or any other sum due under this
Lease.

          Section 3.3.   Consecutive Late Payments. If Tenant fails in two (2)
                         -------------------------
consecutive months to make Rent payments within five (5) days after the date
when due, Landlord may require that future Rent payments be paid quarterly in
advance instead of monthly and/or that all future Rent payments be made on or
before the due date by cash, cashier's check, or money order (in which event,
the delivery of Tenant's personal or corporate check will no longer constitute a
payment of Rent under this Lease). The election by Landlord to exercise either
or

                                       8
<PAGE>

both of the foregoing remedies shall be made by written notice to Tenant and
shall be in addition to any interest and late charges accruing under Section
3.2, as well as any other rights and remedies accruing as a result of such
default.  Any acceptance of a monthly Rent payment in the form of a personal or
corporate check by Landlord thereafter shall not be construed as a subsequent
waiver of these rights.

          Section 3.4.   Security Deposit. The parties have agreed that [*]
                         ----------------
Security Deposit will be required of Tenant at the outset of this Lease.
However, if Tenant is late in paying monthly rentals in two (2) consecutive
months, or if Tenant is late paying monthly rentals three (3) or more times in a
twelve (12) month period, then Landlord reserves the right at such time to
demand (in writing) that a Security Deposit in the amount of [*] the average
monthly rental payments be deposited with Landlord and retained for the
remainder of the Lease Term. Tenant hereby grants to Landlord a security
interest in the Security Deposit. Landlord shall have, and Landlord expressly
retains and reserves, all rights of setoff, recoupment, and similar remedies
available to Landlord under applicable laws or in equity. Landlord may commingle
the Security Deposit with its other funds and shall receive and hold the
Security Deposit without liability for interest. Upon default by Tenant,
Landlord may from time to time, and without prejudice to any other remedy, use
the Security Deposit to the extent necessary to make good any arrears of Rent or
other sums then due from Tenant to Landlord or to pay the cost of any damage,
injury, expense, or liability caused by any default by Tenant under this Lease.
After any such application of any portion of the Security Deposit, Tenant shall
pay to Landlord, immediately upon demand, the amount so applied so as to restore
the Security Deposit to its original amount; and such amount shall then be
deemed to be part of the Security Deposit. Tenant's failure to restore the
Security Deposit may, at Landlord's sole option, constitute a default under this
Lease. If Tenant is not in default under this Lease and after application of the
Security Deposit to the repair of any damage or injury to the Project caused by
Tenant or by any Tenant Related Party, any remaining balance of the Security
Deposit held by Landlord shall be returned by Landlord to Tenant within a
reasonable period of time after the expiration or termination of this Lease. The
Security Deposit shall not be considered an advance payment of rental or a
measure of Landlord's damages resulting from a default by Tenant.

          Section 3.5.   Tenant's Proportionate Share of Taxes, Insurance Costs
                         ------------------------------------------------------
and Utility Costs. In addition to the payment of the Base Rent, Tenant shall pay
-----------------
to Landlord Tenant's Proportionate Share of Utility Costs, Insurance Costs, and
Taxes in accordance with the following provisions:

                    (a)  Tenant shall pay to Landlord, either in the form of a
lump sum payment due and payable within twenty (20) days of receipt of invoice
by Landlord or on a monthly basis contemporaneously with the payment of Rent, as
Landlord may elect, (i) an amount reasonably estimated by Landlord to be
Tenant's Proportionate Share of all Utility Costs for each calendar year or
portion thereof during the Lease Term, (ii) an amount reasonably estimated by
Landlord to be Tenant's Proportionate Share of all Insurance Costs for each
calendar year or portion thereof during the Lease Term, and (iii) an amount
reasonably estimated by Landlord to be Tenant's Proportionate Share of the
amount, if any, by which Taxes for each calendar year or portion thereof during
the Lease Term exceeds Taxes for the Base Year.

*CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       9
<PAGE>

          (b)       If at any time Landlord shall have reasonable grounds to
believe that actual Utility Costs, Insurance Costs, or Taxes will vary from such
estimates, then Landlord reserves the right to revise such estimates
accordingly. Upon any such revision, Landlord may, at Landlord's election,
either (i) require Tenant to make a lump sum payment to Landlord reflecting such
revised estimate or (ii) require Tenant to make the monthly payments due and
payable to Landlord by Tenant under this Section be revised to an amount which
will amortize such revised estimate over the remainder of the calendar year in
which any such revision is made by Landlord.

          (c)       Within sixty (60) days after the end of any calendar year
during which such payments were made by Tenant, a lump sum payment (or credit
against the next succeeding installments of Base Rent, if any, in case of
amounts owed by Landlord to Tenant) shall be made by Tenant to Landlord or by
Landlord to Tenant, as the case may be, so that Tenant shall have paid to
Landlord only Tenant's Proportionate Share of (i) Utility Costs for the previous
calendar year, (ii) Insurance Costs for the previous calendar year, and (iii)
the amount, if any, by which Taxes for the previous calendar year exceed Taxes
for the Base Year, which obligation to make such reconciliation payment to
Landlord or Tenant shall survive the termination of the Lease.

          (d)       Tenant is aware that the provisions of (S) 41.413 the Texas
Property Tax Code (that statute or any successor thereto, being the "Protest
Provision") provides tenants with the right to protest ad valorem real estate
taxes under certain circumstances. Because Tenant recognizes that (a) due to the
size of the Project and the number of tenants who are or will be occupying space
in the Project during the Lease Term, Tenant's share of any Taxes will be
relatively small and (b) the confusion which could result if several tenants
file a real estate tax protest with respect to the Project, Tenant waives its
rights under the Protest Provision to the fullest extent allowed by law. In the
event that Tenant's rights under the Protest Provision cannot be waived, Tenant
will not protest any valuation of the Project unless Tenant notifies Landlord of
Tenant's intent to do so and Landlord then fails to protest that valuation
within thirty (30) days after Landlord receives Tenant's written notice. If
Tenant files a protest under the Protest Provision without giving the required
notice to Landlord, such filing shall, at Landlord's sole election, constitute a
default under this Lease; and no cure period shall be applicable to such
default. In addition, if Tenant exercises the right to protest under this
Protest Provision, Tenant shall pay all costs of such protest and, if the Taxes
are increased following that tax protest, Tenant shall pay such excess Taxes
until the determination of the appraised value of the Project is changed by the
appraisal review board, regardless of whether the increased Taxes are incurred
during the Lease Term or thereafter.

                                   ARTICLE 4

                        BUILDING SERVICES AND UTILITIES

     Section 4.1.   Services to be Furnished by Landlord to Tenant. Landlord
                    ----------------------------------------------
shall furnish Tenant (subject to the terms and conditions of this Article 4)
with the following services ("Building Standard Services") during the Lease
Term:

                                       10
<PAGE>

               (a)  Central Heating and air conditioning in season to the
enclosed public areas of the Building;

               (b)  Non-exclusive passenger escalator and/or elevator services
and non-exclusive freight elevator service;

               (c)  Maintenance and repair of the roof, exterior walls, and
public areas of the Building and electric lighting for all public areas of the
Building;

               (d)  Janitorial service for the corridors and other public areas
of the Building; and;

               (e)  Common use rest rooms and drinking fountains at locations
provided for general use of the tenants in the Building and their guests and
invitees.

The Building Standard Services shall be provided (i) during the hours and days
which Landlord establishes from time to time as the normal business hours of the
Building; (ii) at such locations, in such manner, and to the extent deemed by
Landlord to be reasonably adequate for the use and occupancy of the Building,
and with due regard for the prudent control of energy; (iii) subject to
temporary cessation for ordinary repair, maintenance, and cleaning and during
times when life safety systems override normal Building operating systems; and
(iv) subject to the other limitations described in this Article 4.

Landlord recognizes that Tenant has the right to operate in the Premises twenty-
four (24) hours a day, seven (7) days a week.

     Section 4.2.   Utilities. Landlord has caused the necessary mains,
                    ---------
conduits, and other facilities necessary to supply normal water, electricity,
telephone service, and sewage service to the Building. Landlord shall maintain
those facilities within the Building but shall have no responsibility with
respect to any of those facilities located outside the boundaries of the
Project. To the extent the Building Standard Services require electricity,
water, or other specified utilities supplied by public utilities, Landlord's
obligations under this Lease shall only require Landlord to use reasonable
efforts to cause the applicable public utilities to furnish those utilities; and
Landlord shall not be responsible for, and shall have no liability with respect
to, the quality, quantity, or condition of any services provided by such public
utilities.

     Section 4.3.   Electrical Services. The facilities furnishing electrical
                    -------------------
service to the Building have the capacity for furnishing electricity in the
amount of seven (7) watts per Usable Square Foot within the Premises ("Building
Standard Capacity") and Tenant's Proportionate Share of Utility costs will be
calculated on the basis that Tenant's electrical usage in the Premises is equal
to the Building Standard Capacity. Landlord shall allow electrical services to
the Premises to be provided from a mutually agreed upon transformer pad which is
to be installed by Tenant as a part of the Initial Improvements. Such
transformer pad and installed transformers shall serve the Premises with a
dedicated access of not less than 56 watts per the Usable Square Feet within the
Premises ("Approved Electrical Capacity"); and Tenant's lighting and
receptacle/equipment loads in the Premises shall not have an electrical design
load greater than the Approved Electrical Capacity. In the event Tenant's actual
electrical usage within the Premises exceeds the Approved Electrical Capacity,
such excess electrical usage may

                                       11
<PAGE>

affect the capability of such electrical systems to furnish electricity to other
tenants of the Building at the Building Standard Capacity. For this reason,
Landlord shall have the right to determine the amount of any electrical usage by
Tenant from time to time and, if such electrical usage by Tenant exceeds the
Building Standard Capacity, may either separately meter Tenant's electrical
usage within the Premises or require Tenant to reduce its electrical usage to
the Building Standard Capacity. The cost of purchasing, installing, maintaining,
and reading a separate meter shall be at Tenant's expense, and Tenant shall pay
to Landlord, on demand, the cost of the consumption of electrical services
within the Premises in excess of the Building Standard Capacity at rates
determined by Landlord in accordance with applicable laws. In addition, Tenant
shall pay for all costs of any wiring, risers, raceways, transformers,
electrical panels, and other items required by Landlord, in Landlord's
discretion, to accommodate Tenant's design loads and capacities that exceed the
Standard Building Capacity, including, without limitation, all installation and
maintenance costs relative to that equipment. Notwithstanding the foregoing,
Landlord may refuse to install, and may withhold consent for Tenant's
installation of, any wiring, transformers, electrical panels, or other equipment
required to accommodate Tenant's excess electrical usage if, in Landlord's sole
judgment, the same are not necessary or would cause damage or injury to the
Project or cause or create a dangerous or hazardous condition or entail
excessive or unreasonable alterations or repairs to the Project, or would
interfere with or create or constitute a disturbance to other tenants or
occupants of the Project. In no event shall Landlord incur any liability for
Landlord's refusal to install, or the withholding of consent for Tenant's
installation of, any such facilities or equipment; and Landlord shall have no
obligation to install any electrical facility or equipment to accommodate
Tenant's electrical usage in excess of the Approved Electrical Capacity.

     Section 4.4.   Adverse HVAC Effect.  Intentionally deleted."
                    -------------------

     Section 4.5.   Interruption of Utilities or Services. In the event that any
                    -------------------------------------
utility services to the Building or the Premises are interrupted, malfunction,
or are subject to partial curtailment; any equipment, machinery, or facility
within the Building furnished by Landlord breaks down or, for any cause, ceases
to function; or an interruption or malfunction occurs with respect to any
Building Standard Service, Landlord shall use reasonable efforts to repair (if
related to facilities or equipment within the Project) or obtain the restoration
of such services as soon as reasonably practicable. No such occurrence, nor
Landlord's compliance with any Legal Requirement or with any voluntary
governmental or business guidelines related to the conservation of energy, shall
ever (a) cause Landlord to be liable or responsible to Tenant for any loss or
damage which Tenant may sustain or incur as a result of any such occurrence, (b)
be construed as an eviction of Tenant or as a disturbance of Tenant's use or
possession of the Premises, (c) constitute a breach by Landlord of any of
Landlord's obligations under this Lease, (d) work an abatement or reduction of
Rent, (e) entitle Tenant to any right of setoff or recoupment, or (f) relieve
Tenant of any of Tenant's obligations under this Lease. Landlord shall, as soon
as reasonably practicable, notify Tenant of any interruption anticipated by
Landlord in any utility services to the Building or the Premises.

     Section 4.6.   Telecommunications. In the event that Tenant desires to
                    ------------------
utilize the services of a telephone or telecommunications provider who is not
then servicing the Project, such provider shall not be permitted to install its
lines or other equipment within the Project without first obtaining the prior
approval of Landlord (including Landlord's approval of any

                                       12
<PAGE>

plans or specifications for the installation of lines and/or other
telecommunications equipment within the Project). Neither Landlord's approval of
any provider nor Landlord's approval of any plans and specifications relative to
the installation of any telecommunications equipment will ever constitute an
indication, representation, or certification by Landlord as to the suitability,
competence, or financial strength of that provider or as to the suitability of
any telecommunications equipment provided. The failure of any provider to
satisfy the standards and conditions set forth in Landlord's "Telecommunications
Provider Requirements" shall constitute reasonable grounds for Landlord's
refusal to approve that provider. Landlord reserves the right to (a) impose
restrictions on any telecommunications provider that are reasonably necessary to
protect the safety, security, appearance, and condition of the Building, and the
safety and convenience of Landlord, tenants of the Building, and other persons;
(b) impose a reasonable limitation on the time during which any
telecommunication provider may have access to the Building to install any of its
telecommunications facilities; (c) impose reasonable limitations on the number
of telecommunications providers that have access to the Building; (d) require
that each telecommunications provider agree to indemnify Landlord for damage
caused in connection with the installation, operation, maintenance, repair, or
removal of any of its telecommunications facilities; (e) require Tenant or the
telecommunications providers selected by Tenant to bear the entire cost of
installing, operating, or removing all of its telecommunications facilities
(including wiring and cabling); and (f) require any telecommunications provider
to pay reasonable compensation to Landlord relevant to its installation.
Landlord shall have no obligation to repair, maintain or replace any
telecommunications facilities or equipment provided by a telephone or
telecommunications provider selected by Tenant, notwithstanding any provision of
this Lease to the contrary.

                                   ARTICLE 5

                    ALTERATIONS, REPAIRS AND TRADE FIXTURES

          Section 5.1.   Alterations, Improvements and Additions.
                         ---------------------------------------

                    (a)  Tenant shall, at Tenant's expense, furnish, equip, and
improve the Premises, to the extent necessary or appropriate for the proper
operation of the Premises for the Permitted Use. Tenant's obligations to provide
leasehold improvements within the Premises shall include partitions, lighting
fixtures, floor and wall coverings, and other interior decoration and shall be
of a design and quality consistent with the standards generally observed by
Landlord and other tenants of the Building.

                    (b)  All work to be done to improve, equip, or alter the
Premises and any work in any other areas of the Project for which Tenant is
responsible shall be subject to the following conditions:

                         (i)       all such work shall be done at Tenant's sole
cost, risk, and expense and in accordance with all Legal Requirements, Insurance
Requirements, Building Rules, and construction guidelines and standards of
Landlord;

                                       13
<PAGE>

                         (ii)      all such work shall be performed in a good
and workmanlike manner with labor and materials of such quality as Landlord may
reasonably approve;

                         (iii)     no such work shall be commenced until
approved in writing by Landlord. Notwithstanding the foregoing, Landlord shall
not unreasonably withhold its consent with respect to any alteration of the
Premises which (A) does not involve work above the ceiling of the Premises, or
(B) does not affect, in any way, the mechanical, electrical, plumbing and/or
structural components of the Building and Landlord's consent shall not be
required for work occurring entirely within the Premises which is necessary with
respect to electrical, mechanical, or security services provided by Tenant to
its Customers and provided that the requirements of clauses (A) and (B) in this
sentence are satisfied;

                         (iv)      all such work shall be performed in strict
accordance with the plans and/or specifications previously approved by Landlord;

                         (v)       all such work shall be prosecuted diligently
and continuously to completion;

                         (vi)      all such work shall be performed in a manner
so as to minimize interference with the normal business operations of other
tenants in the Building; the performance of Landlord's obligations under this
Lease, any other lease for space in the Building, or any Financing Lien or
Ground Lease covering or affecting all or any part of the Project; and any work
being done in any other portion of the Project;

                         (vii)     Landlord may impose such conditions with
respect to such work as Landlord deems reasonably appropriate, including,
without limitation, (A) requiring Tenant to furnish Landlord with security for
the payment of all costs to be incurred in connection with such work and (B)
requiring Tenant or Tenant's contractor to maintain insurance against
liabilities which may arise out of such work;

                         (viii)    such work shall be performed by contractors
approved in writing by Landlord and, if requested by Landlord, any such
contractor and all work to be performed by such contractor shall be fully bonded
(with Landlord named as co-obligee) with companies and in amounts acceptable to
Landlord in its reasonable discretion; and

                         (ix)      upon completion of any such work and upon
Landlord's request, Tenant shall deliver to Landlord evidence of payment,
contractors' affidavits, and full and final waivers of all liens for labor,
services, or material.

                    (c)  No alterations, improvements, or additions made to the
Premises by or on behalf of either Landlord or Tenant may be removed by Tenant
without Landlord's prior written consent. All such alterations, improvements, or
additions shall become the property of Landlord upon the termination or
expiration of this Lease. Tenant shall have no (and hereby waives all) rights to
payment or compensation for any such alteration, improvement, or addition to the
Premises. However, Tenant's Trade Fixtures shall remain the property of Tenant
as provided in Section 5.3 below.

                                       14
<PAGE>

                    (d)  Tenant shall not allow any liens to be filed against
the Premises or the Project in connection with the installation of any
alterations, improvements, or additions to the Premises. If any such liens shall
be filed, Tenant shall cause the same to be released immediately by payment,
bonding, or other method acceptable to Landlord. If Tenant shall fail to cancel
or remove any lien, then Landlord, at its sole option, may obtain the release of
that lien; and Tenant shall pay to Landlord, on demand, the amount incurred by
Landlord for the release of each lien, plus an additional charge (as determined
by Landlord) to cover Landlord's administrative overhead and expenses.

                    (e)  Tenant hereby indemnifies and holds Landlord harmless
from all losses, costs, damages, claims, expenses (including attorneys' fees and
costs of suit), liabilities, or causes of action arising out of or relating to
any alterations, additions, or improvements that Tenant makes or causes to be
made to the Premises or to any repairs made to any portion of the Project,
including any occasioned by the filing of any mechanic's, materialman's,
construction, or other liens or claims (and all costs or expenses associated
with any such lien or claim) asserted, filed, or arising out of such work.
Nothing contained in this Lease shall be deemed or construed in any way as
constituting the consent of or request by Landlord, express or implied, to any
contractor, subcontractor, laborer, or materialman for the performance of any
labor or the furnishing of any materials for the improvement, alteration, or
repair of the Premises or the Project or as giving Tenant any right or authority
to contract for or permit the rendering of any labor or the furnishing of any
materials that would give rise to a lien against the Premises or the Project.

                    (f)  Tenant shall have the sole responsibility for
compliance with all applicable Legal Requirements and Insurance Requirements
relative to any such alterations, improvements, or additions. Landlord's
approval of any plans or specifications shall never constitute an indication,
representation, or certification that such alterations, improvements, or
additions will be in compliance with any applicable Legal Requirement or
Insurance Requirement or as to the adequacy or sufficiency of the alterations,
improvements, or additions to which such consent relates. In instances in which
several sets of requirements must be met, the strictest applicable requirements
shall control.

                    (g)  Tenant shall not permit any weight exceeding two
hundred fifty (250) pounds per square foot of floor area upon the floor of the
Premises.

          Section 5.2.   Maintenance and Repairs. Tenant shall take good care of
                         -----------------------
and maintain the Premises (including all plate glass, Trade Fixtures, and
improvements, additions, or alterations situated in the Premises) in a first
class, clean, and safe condition other than damage caused by the negligence of
Landlord. Tenant shall not commit or allow any waste or damage to be committed
on any portion of the Premises or the Project. Tenant shall repair or replace
any damage to any part of the Project, caused by Tenant or by a Tenant Related
Party. However, Landlord may, at its option, make such repairs, improvements, or
replacements; and Tenant shall repay Landlord on demand the actual costs
incurred by Landlord to make such repairs, improvements, or replacements plus an
additional charge (as determined by Landlord) to cover administrative overhead.
Landlord shall arrange for the repair and maintenance of the foundation,
exterior walls, and roof of the Building; the public areas within the Building;
the heating, air conditioning, and ventilation system within the Building; and
the facilities providing

                                       15
<PAGE>

utility services (other than facilities installed by a telephone or
telecommunications provider selected by Tenant) which are located within the
Project (collectively, "Landlord's Repair Obligations"). Landlord, however,
shall not be required to make any repairs arising as a result of, in whole or in
part the act or negligence of Tenant or any Tenant Related Party; and the cost
of those repairs shall be the obligation of Tenant. In the event that the
Premises become in need of repairs which are within Landlord's Repair
Obligations, Tenant shall give immediate notice to Landlord of the nature of
such repair needs; and Landlord shall not be responsible in any way for failure
to make any repairs until a reasonable time shall have elapsed after receipt by
Landlord of such written notice.

          Section 5.3.   Trade Fixtures. All Trade Fixtures shall be and remain
                         --------------
the property of Tenant and may be removed by Tenant prior to or upon the
expiration or termination of this Lease. Tenant shall repair any damage caused
by such removal and restore the Premises to the condition existing prior to the
installation of those Trade Fixtures. Any Trade Fixtures which are not removed
from the Premises upon the expiration or termination of this Lease shall be
deemed to have been abandoned by Tenant and shall, at Landlord's option, become
the property of Landlord. In that event, Tenant shall have no (and hereby waives
all) rights to payment or compensation for any such item.

          Section 5.4.   Surrender of Premises. Upon the expiration or
                         ---------------------
termination of this Lease, Tenant shall surrender the Premises to Landlord,
broom-clean and in a good state of repair and condition, excepting only ordinary
wear and tear. Upon request of Landlord, Tenant shall (a) demolish or remove all
or any portion of any Trade Fixtures and other property and all alterations,
improvements, or additions to the Premises made by or on behalf of Tenant and
(b) restore the Premises to the condition existing prior to the installation of
those Trade Fixtures or other property or the making of any such alterations,
improvements, or additions. Upon the expiration or termination of this Lease,
Tenant will deliver all keys to the Premises to Landlord and inform Landlord of
all combinations on locks, safes, and vaults, if any, which remain in the
Premises.

                                   ARTICLE 6

                          RIGHTS RESERVED BY LANDLORD

          Section 6.1.   Landlord's Access. Landlord (and its agents,
                         -----------------
representatives, and contractors) shall have the right to enter upon the
Premises with forty-eight (48) hours prior written to Tenant (and, in the case
of an emergency, at any time) to (a) inspect the Premises; (b) make repairs,
alterations, or additions; and (c) within six (6) months prior to the expiration
of the Lease Term, show the Premises to prospective tenants, subtenants,
mortgagees, and purchasers as Landlord may deem necessary or desirable. Except
in case of emergency, Tenant shall have the right to have a representative
present during any such entry into the Premises by Landlord Tenant shall not be
entitled to any abatement or reduction of any Rent by reason of any such entry
by Landlord, and no such entry shall ever be construed to be an eviction of
Tenant, a default by Landlord, or a breach of the covenant of quiet enjoyment.
In exercising its rights under this Section 6.1, Landlord shall use reasonable
efforts to avoid (to the extent reasonable and practicable under the
circumstances) material interference with Tenant's Permitted Use of the
Premises.

                                       16
<PAGE>

          Section 6.2.   Assignment, Subletting, or Other Transfers by Tenant.
                         ----------------------------------------------------
Landlord reserves the right to approve any transfers of any interest of Tenant
under this Lease. Tenant shall not, without having obtained Landlord's prior
written consent, (a) assign, convey, or otherwise transfer (whether voluntarily,
by operation of law, or otherwise) this Lease, the Premises, or any interest of
Tenant under this Lease, (b) mortgage, pledge, or otherwise encumber any
interest of Tenant under this Lease, (c) grant any concession or license within
the Premises, (d) grant or transfer any management privileges or rights with
respect to the Premises, (e) allow any lien, security interest, or other
encumbrance to be placed upon any interest of Tenant under this Lease, (f)
sublet all or any part of the Premises, or (g) permit any other party to occupy
or use all or any part of the Premises. Any attempted transfer by Tenant without
Landlord's prior written consent shall be of no force or effect and may, at
Landlord's option, be a default by Tenant under this Lease. If Tenant is other
than a natural person and if Tenant's voting securities are not traded on a
national securities exchange, any conveyance, assignment, or transfer of more
than a fifty-five percent (55%) interest in Tenant in a single transaction or in
a series of transactions shall be deemed an assignment prohibited by this Lease.
In the event of a transfer of any interest of Tenant under this Lease (whether
with or without Landlord's consent), (h) each transferee shall fully observe all
covenants and obligations of Tenant under this Lease; (i) no transferee shall
use the Premises for any use except the Permitted Use; (j) such transfer shall
be subject to all of the terms, covenants, and conditions of this Lease; (k) any
transferee must assume in writing all of the applicable obligations of the
Tenant under this Lease; and (l) any expansion, renewal, or like options granted
to Tenant under this Lease shall automatically terminate as of the date of such
transfer. No such transfer shall ever be construed to constitute a waiver of any
of Tenant's covenants contained in this Lease, a release of Tenant from any
obligation or liability of Tenant under this Lease, or a waiver of any of
Landlord's rights under this Lease. The consent by Landlord to a particular
transfer shall not constitute Landlord's consent to any other or subsequent
transfer. No transferee of Tenant shall have any right to further sublease or
assign, or otherwise transfer, encumber, pledge, or mortgage its interest under
this Lease. Neither the voluntary or other surrender of this Lease by Tenant nor
a mutual cancellation of this Lease shall ever constitute a merger of estates.
Instead, any such early termination of this Lease shall, at the option of
Landlord, either terminate all or any existing subleases or subtenancies or
operate as an assignment to Landlord of Tenant's interest in any or all such
subleases or subtenancies.

          Notwithstanding any provision of this Lease to the contrary, Tenant
shall have the right, without obtaining the prior written consent of Landlord,
to assign this Lease or sublet the Premises to (a  any parent corporation of
Tenant, (b) any subsidiary corporation of Tenant or of Tenant's parent
corporation, (c) any entity in which Tenant, any parent corporation of Tenant or
any subsidiary corporation of Tenant or of Tenant's parent corporation holds a
majority of the outstanding shares or ownership interests, or (d) any
corporation resulting from the merger, consolidation or reorganization of Tenant
or Tenant's parent corporation with another corporation (collectively,
"Affiliates"), but only if such Affiliate is "Credit Worthy" as of the date of
such assignment or subleasing.  As used herein, "Credit Worthy" shall mean that
such Affiliate's has a net worth equal to not less than $5,000,000.00. Landlord
agrees to release Tenant from all obligations under this Lease in the event the
obligations of Tenant under this Lease are assumed under the provisions of the
preceding sentence by a corporation whose Landlord acknowledges that Tenant's
business to be conducted on the Premises requires the installation on the
Premise of certain communications equipment by certain licensees and

                                       17
<PAGE>

customers of Tenant (collectively, "Customers") in order for such Customers to
interconnect with Tenant's terminal facilities or to permit Tenant to manage or
operate such Customers' equipment, or otherwise as may be required pursuant to
applicable statures and regulations. Notwithstanding anything to the contrary in
this Lease, Landlord hereby consents in advance to any sublease, license
agreement, co-location agreement or similar agreement (collectively, "Customer
License") between Tenant and such a Customer for the limited purpose of
permitting such arrangements as described above. Any and all of the transactions
permitted under this Section 6.2 shall not constitute an assignment, subletting
or other transaction requiring the consent of Landlord under the provisions of
this Section 6.2 and shall not be subject to any of the other provisions of this
Section 6.2.

          Notwithstanding the provisions of this Section 6.2, Landlord shall not
unreasonably withhold its consent in connection with an assignment of this Lease
or a subletting of all or any portion of the Premises to a qualified third party
if (i) rent is to be at not less than the then market rate for comparable space
within the Building, (ii) Landlord receives evidence satisfactory to Landlord
that such proposed third-party is "Creditworthy" (as defined above), (iii)
Landlord receives evidence satisfactory to Landlord that the proposed subtenant
or assignee will immediately occupy and thereafter use the Premises, or
applicable portion thereof, in accordance with the Permitted Use for the
remainder of the Lease Term, or for the entire term of any sublease, if such
expires prior to the expiration of the Lease Term, and (iv) the occupancy of the
Premises, or applicable portion thereof, by the proposed third-party would not
increase fire hazards, require substantial alterations to the Premises, or
applicable portions thereof, reduce the rental value of rentable space within
the Building, or adversely affect the reputation and image of the Building.  In
no event shall Landlord be deemed to have unreasonably withheld consent to an
assignment or sublease to a third party who is owned or controlled by a foreign
government, involved in lobbying activities, or reputed to be involved in
illegal or illicit activities.  Under no circumstances shall Tenant have the
right, without first obtaining Landlord's prior consent, to advertise or to
engage in any other promotional activities regarding an assignment or subletting
of all or any portion of the Premises.

          Landlord and Tenant shall divide equally the excess rentals from any
approved assignee or sublessee (such excess to be the amount which equals the
difference between the rentals or other consideration actually paid by such
assignee or sublessee to Landlord less the [i] rentals required to be paid by
Tenant hereunder, [ii] the brokerage commissions paid by Tenant in connection
with such assignment or sublease, and [iii] attorneys' fees paid by Tenant in
connection with such sublease or assignment).

          Section 6.3.   Assignment by Landlord. Landlord shall have the right
                         ----------------------
at any time to transfer and assign, in whole and by operation of law or
otherwise, Landlord's rights, benefits, privileges, duties, and obligations
under this Lease, in the Building, or in any portion of the Project. Landlord
shall be released from any further obligation under this Lease, and Tenant
agrees to look solely to Landlord's successor in interest for the performance
of, all obligations of Landlord accruing subsequent to the date of such
transfer. All covenants of Landlord under this Lease shall be binding upon
Landlord and its successors only with respect to breaches occurring during its
or their respective periods of ownership of Landlord's interest under this
Lease.

                                       18
<PAGE>

          Section 6.4.  Alterations and Additions by Landlord. Landlord reserves
                        -------------------------------------
the right to make alterations or additions to the Project at any time and from
time to time. Landlord further reserves the right to construct (or permit others
to construct) other buildings or improvements within the Project at any time and
from time to time. Such rights set forth in the two preceding sentences include
the right to construct additional stories to any building within the Project,
the right to build adjoining buildings, the right to construct multi-level,
elevated, underground, and other parking facilities within the Project, and the
right to erect or build temporary scaffolds or other aids to such construction.
Neither the diminution nor the shutting off of any light, air, or view nor any
other effect on the Premises as a result of Landlord's exercise of the rights
reserved in this Section 6.4 shall affect this Lease, abate or reduce Rent, or
otherwise impose any liability on Landlord provided Landlord's exercise of such
rights does not materially interfere with Tenant's Permitted Use of or access to
the Premises.

          Section 6.5. Subordination to Mortgages and Leases. This Lease shall
                       -------------------------------------
be subject and subordinate at all times to (a) all ground or underlying leases
now existing or which may be subsequently executed affecting the Project
("Ground Lease"), (b) the lien or liens of all mortgages and deeds of trust now
existing or subsequently placed on the Project or Landlord's interest or estate
in the Project ("Financing Lien"), and (c) all renewals, modifications,
consolidations, replacements, and extensions of any Ground Lease or Financing
Lien. The provisions of this Section shall be self-operative without the
necessity of the execution of any other document by any party. However, Tenant
shall execute and deliver any instruments, releases, or other documents
requested by Landlord for the purpose of confirming the provisions of this
Section or further subjecting and subordinating this Lease to any Ground Lease
or Financing Lien. In the event of the enforcement by the lessor under any
Ground Lease or by the holder of any Financing Lien of the remedies provided for
by law or by such Ground Lease or Financing Lien, or in the event of the
transfer of the Building or Landlord's interest or estate in any part of the
Building by deed in lieu of foreclosure, Tenant, upon request of any person or
party succeeding to the interest of Landlord as a result of such enforcement or
deed in lieu of foreclosure, automatically will become the tenant of such
successor in interest without change in the terms or provisions of this Lease.
However, such successor in interest shall not be bound by any payment of Rent
for more than one (1) month in advance, except prepayments in the nature of
security for the performance by Tenant of its obligations under this Lease which
have been actually delivered to such successor; liable for the return of any
security deposit or other deposit unless such security deposit or other deposit
has actually been delivered to such successor; or bound by any amendment or
modification of this Lease made after the applicable Ground Lease or Financing
Lien is placed against the Project without the written consent of any trustee,
mortgagee, beneficiary, or lessor. Contemporaneously with Tenant's execution of
this Lease, Tenant shall execute and deliver an instrument ("SNDA"), in the form
attached hereto as Exhibit "F", confirming the attornment and other agreements
contemplated by this Section. Notwithstanding anything to the contrary set forth
in this Lease, the lessor under any Ground Lease or the holder of any Financing
Lien may elect at any time to cause their interest in the Project to be
subordinate to Tenant's interest under this Lease by filing an instrument in the
real property records of Dallas County, Texas, affecting such election; and
Tenant shall execute and deliver to Landlord immediately any such instruments or
documents requested by the lessor under such Ground Lease or the holder of such
Financing Lien for the purpose of confirming that such Ground Lease or Financing
Lien is subordinated to Tenant's interest under this Lease. Provided that Tenant
executes and delivers the SNDA to Landlord, Landlord shall, upon

                                      19

<PAGE>

execution of this Lease by Landlord, execute the SNDA and deliver the SNDA to
the current holder of the Financing Lien on the Project, with the request that
such current holder of the Financing Lien execute and return a fully executed
copy of the SNDA to Landlord. Within ninety (90) days of Landlord's submission
of the partially executed SNDA to the current holder of the Financing Lender,
Landlord shall obtain, and deliver to Tenant, a fully executed copy of the SNDA.
In addition, Landlord will use its reasonable efforts to obtain a non-
disturbance agreement from any future holder of a Financing Lien on the Project,
which shall be acceptable to Tenant if in form and content, except for the
completion of the applicable blanks therein and the identity of the holder of
the Financing Lien, reasonably comparable to the SNDA. Landlord's obligation to
use reasonable efforts to obtain a non-disturbance agreement from future holders
of a Financing Lien shall not, however, require Landlord to forego future
financing or refinancing relative to the Project or a prospective sale of the
Project; and Landlord shall have the sole and absolute discretion to determine
at what point in the negotiation process to withdraw or waive Landlord's request
that such lender execute a non-disturbance agreement.]

          Section 6.6. Certificates. Within ten (10) days after Landlord's
                       ------------
written request, Tenant will execute, acknowledge, and deliver to Landlord (and
any other persons specified by Landlord) a certificate certifying as to such
facts (to the extent true) as Landlord may reasonably request, including (a)
that this Lease is in full force and effect, (b) the date and nature of each
modification to this Lease, (c) the date to which Rent and other sums payable
under this Lease have been paid, and (d) that Tenant is not aware of any default
under this Lease which has not been cured, except such defaults as may be
specified in said certificate. Such request may be made by Landlord at any time,
and from time to time, during the Lease Term. Any such certificate may be relied
upon by Landlord and by such other persons specified by Landlord or to whom such
certificate may be delivered. Tenant's failure to deliver any such certificate
within the specified time period shall constitute a representation by Tenant
that all factual statements made by Landlord relative to those matters are true
and correct and may be relied upon by any person. Likewise, within ten (10) days
after Tenant's request, Landlord will execute, acknowledge, and deliver to
Tenant (and any other person specified by Tenant) a certificate certifying as to
(a) the date to which Rent has been paid and (b) that Landlord is not aware of
any default under the Lease that has not been cured, except such defaults as may
be specified in said certificate. This request may be made by Tenant at any
time, and from time to time, during the Lease Term. Any such certificate may be
relied upon by Tenant and by such other persons specified by Tenant or to whom
such certificate may be delivered.

          Section 6.7. Building Rules. Landlord reserves the right to rescind
                       --------------
any of the Building Rules and to make any modifications or additions to the
Building Rules as shall be necessary or advisable for the safety, protection,
care, and cleanliness of the Building and the Project, the operation of the
Project, the preservation of good order in the Project, the protection and
comfort of the tenants in the Building (and their agents, employees, and
invitees), and the reputation of the Project. All amendments, modifications, and
additions to the Building Rules shall be binding upon Tenant from the date on
which notice of any such Building Rules is delivered to Tenant. While the
Building Rules are intended to be of general applicability to all tenants of the
Building, Landlord reserves the right to waive the applicability of any one or
more of the Building Rules to a particular situation, but such waiver by
Landlord shall not be construed as a waiver of such Building Rules with respect
to any other comparable situation and shall not prevent Landlord from thereafter
enforcing any of such Building Rules against or any

                                      20

<PAGE>

or all of the tenants in the Building. If there is any conflict between any
subsequently enacted Building Rules and the terms and provisions of this Lease,
the terms and provisions of this Lease shall control.

          Section 6.8. Use of the Term "INFOMART". Landlord reserves the right
                       --------------------------
to approve Tenant's usage of the term "INFOMART", and Tenant shall not use the
term "INFOMART" in any of its activities (including advertising and marketing
activities) without the prior written consent of Landlord. Copies of all
proposed written materials and advertising containing references to the term
"INFOMART" shall be furnished to Landlord in advance for its review and
approval. Any permitted use of the term "INFOMART" by Tenant shall additionally
include the phrase "The Technology Community" immediately after such use. Tenant
shall not permit any third party to use the term "INFOMART" in any of its
activities and shall report to Landlord any unauthorized uses of such term as it
comes to its attention. The breach by Tenant of any provision in this Section
6.8 shall constitute an event of default under this Lease and shall entitle
Landlord to exercise any right or remedy available to Landlord under this Lease,
at law, or in equity. Tenant shall indemnify and hold Landlord harmless from and
against any loss, cost, claim, liability, cause of action, or expense whatsoever
(including attorney's fees and other costs and expenses of defending any such
claim) arising or alleged to arise from any unauthorized use by Tenant, or any
Tenant Related Party, of the term "INFOMART".

                                   ARTICLE 7

                           CONDEMNATION AND CASUALTY

          Section 7.1.  Condemnation. In the event of a Total Taking of the
                        ------------
Premises or the Building, then this Lease shall terminate as of the date when
physical possession of the Premises or Building, as applicable, is taken by the
condemning authority. If a Partial Taking occurs which relates to a material
portion of the Building or if Landlord is required to pay any of the proceeds
from such Partial Taking to the lessor under a Ground Lease or to the holder of
a Financing Lien, then this Lease, at the option of Landlord, exercised by
written notice to Tenant within thirty (30) days after the date of such Partial
Taking, shall terminate regardless of whether the Premises are affected by such
Partial Taking. In this event, Rent shall be apportioned as of the date when
physical possession of the applicable portion of the Building is taken by the
condemning authority. In the event of a Partial Taking of the Premises which
results in the Premises being Untenantable, then Tenant may terminate this Lease
as of the date of such Taking by giving Landlord written notice of Tenant's
termination election within thirty (30) days after the date of such Taking; and
Rent shall be apportioned as of the date of such Taking. If a Taking of the
Premises occurs which entitles Tenant to terminate this Lease but Tenant does
not do so in the manner and within the time period specified in the immediately
preceding sentence, then Tenant shall be deemed to have irrevocably waived its
termination right. If Tenant is deemed to have waived its termination right or
if a Partial Taking of the Premises occurs which does not result in the Premises
becoming Untenantable, then Landlord shall allow Tenant a fair diminution of
Rent as to that portion of the Premises subject to such Taking; and this Lease
shall otherwise continue in full force and effect. All proceeds (whether in a
lump sum or in separate awards) of any Taking shall be paid to Landlord, and
Tenant shall not be entitled to (and expressly waives any claim to) any portion
of Landlord's award. However, Tenant shall have the right to assert a separate
claim for any loss resulting to Tenant from such Taking if, and only

                                      21

<PAGE>

if, that claim does not in any way adversely affect the amount of Landlord's.
The term "Taking" means a transfer during the Lease Term of all or any part of
the Premises, the Building, or the Project, as applicable, as a result of, or in
lieu of or in anticipation of, the exercise of the right of condemnation or
eminent domain for any public or quasi-public use under any governmental law,
ordinance, or regulation. The term "Partial Taking" means a Taking of less than
the whole or substantially the whole of the Building and/or the Premises. The
term "Total Taking" means a Taking of the whole or substantially the whole of
the Building or the Premises or to a Taking which results in the termination of
an applicable Ground Lease. "Untenantable" shall mean that Tenant is unable to
conduct its business in the Premises in a manner reasonably comparable to that
conducted immediately before the applicable occurrence.

          Section 7.2.  Casualty Damage. If the Premises shall be destroyed or
                        ---------------
damaged by fire or any other casualty, Tenant shall immediately give written
notice of that occurrence to Landlord. In the event that any portion of the
Project is damaged by fire or other casualty and if (a) such damage is such that
Landlord cannot reasonably be expected to substantially complete the repairs
which are within Landlord's Repair Obligations within two hundred forty (240)
days after the date of the casualty; (b) if, and only if, such casualty results
in material damage to the Project, Landlord, in Landlord's sole judgment, elects
not to repair or rebuild such damaged areas; or (c) less than one (1) year
remains in the Lease Term at the time of any damage to the Project, then
Landlord, at Landlord's sole option, shall have the right to terminate this
Lease, regardless of whether the Premises are affected by such casualty. In such
event, all Rent owed up to the date of that casualty shall be paid by Tenant to
Landlord; and this Lease shall cease and come to an end as of the date of
Landlord's written notice to Tenant regarding such termination. In the event
that (x) the Premises is rendered Untenantable by fire or any other casualty
which is not caused by the fault or neglect of Tenant or any Tenant Related
Parties; (y) such damage is such that Landlord cannot reasonably be expected to
substantially complete the repairs within the Premises which are within
Landlord's Repair Obligations within two hundred forty (240) days after the date
of that casualty, as reasonably estimated by Landlord; and (z) Landlord has not
terminated this Lease, then Tenant shall have the right to terminate this Lease
by delivering written notice to Landlord within thirty (30) days after receipt
of written notice of Landlord's estimate of the time to complete Landlord's
Repair Obligations relative to the Premises. If Tenant does not provide Landlord
with notice of Tenant's termination election in the manner and within the time
period specified in the preceding sentence, then Tenant shall be deemed to have
irrevocably waived its right to terminate the Lease as a result of such
casualty; and Landlord, in reliance upon Tenant's waiver of its termination
right, shall proceed to make the repairs which are within Landlord's Repair
Obligations. During any period of reconstruction or repair of the Premises,
Tenant shall continue the operation of Tenant's business within the Premises to
the extent practicable. During the period from the occurrence of a casualty
which was not caused, in whole or in part, by Tenant or any Tenant related
party, until the completion of the work within Landlord's Repair Obligations
which is necessary to render the Premises tenantable, Rent shall be reduced to
the extent that the Premises are unfit for the conduct of Tenant's Permitted Use
of the Premises. If, however, the Premises or any portion of the Project is
damaged by fire or other casualty resulting from the fault or negligence of
Tenant or any Tenant Related Party, the Rent shall not be reduced during the
repair of such damage. If neither Landlord nor Tenant elects, or has the right
to elect, to terminate this Lease as the result of such casualty, then Landlord
shall commence and proceed with reasonable diligence to restore the Premises to
the extent of Landlord's Repair Obligations. When the repairs described in the
preceding sentence have been

                                      22

<PAGE>

completed by Landlord, Tenant shall then complete the restoration of all
leasehold improvements in excess of Landlord's Repair Obligations which are
necessary to permit Tenant to re-occupy the Premises for the Permitted Use.
Tenant's restoration work shall be conducted in accordance with the provisions
of Section 5.1 above. In no event shall Landlord have the obligation to expend
for the restoration or repair of the Project an amount in excess of the
insurance proceeds actually received by Landlord as a result of such casualty;
and except for those repairs which are within Landlord's Repair Obligations, all
costs and expenses of restoring the Premises shall be borne by Tenant. Landlord
shall not be liable for any inconvenience or annoyance to Tenant or injury to
the business of Tenant resulting in any way from any casualty or the repair or
restoration work made necessary by the occurrence of any casualty.

          Section 7.3.  Insurance.
                        ---------
               (a)  Landlord shall not be obligated to insure any of Tenant's
goods, Trade Fixtures, leasehold improvements, or any other property placed in
or incorporated in the Premises by or on behalf of Tenant. Landlord shall
maintain fire and extended coverage insurance on the Building (excluding
leasehold improvements and tenants' personal property) in amounts desired by
Landlord and at the expense of Landlord. All payments for losses thereunder
shall be made solely to Landlord.

               (b)  Tenant shall procure and maintain, at its sole cost and
expense during and throughout the Lease Term, a policy or policies of (i)
commercial general liability insurance in an amount of not less than
$5,000,000.00 (which can be complied with by Commercial General Liability Limits
or by combination with additional Excess or Umbrella [commercial catastrophe]
Liability limits), (ii) fire and extended coverage insurance with respect to
Tenant's Trade Fixtures, inventory, and leasehold improvements located in the
Premises written on an "All Risk" basis for the full replacement cost, (iii)
worker's compensation and employer's liability insurance, and (iv) such other
insurance as Landlord may, from time to time, reasonably require with the
exception of business interruption insurance which Tenant chooses not to carry
coverage. In addition, Tenant shall obtain a fire legal liability endorsement or
other coverage satisfactory to Landlord which removes the "owned, rented, or
occupied" property exclusion from Tenant's liability policy. All such insurance
shall be maintained with companies authorized to transact business in the State
of Texas and of good financial standing on forms and in amounts acceptable to
Landlord. In addition, each such policy, other than the workers
compensation/employers liability policies and policies insuring only Tenant's
Trade Fixtures, shall name Landlord and the Landlord Related Parties as
"additional insureds" thereunder and shall contain a standard "other insurance"
clause, unmodified in any way that would make the coverage provided by the
policy excess over or contributory with any additional insured's own insurance
coverage.

               (c)  All policies of insurance required to be maintained by
Tenant shall provide that Landlord shall be given at least thirty (30) days'
prior written notice of any cancellation or non-renewal of any such policy. A
duly executed certificate of insurance with respect to each such policy shall be
deposited with Landlord by Tenant on or before the Commencement Date, and a duly
executed certificate of insurance with respect to each subsequent policy shall
be deposited with Landlord at least fifteen (15) days prior to the expiration of
the policy then in effect.

                                      23

<PAGE>

               (d)  Tenant shall not do or permit anything to be done in or
about the Premises, nor bring nor keep nor permit anything to be brought to or
kept in the Premises, which will in any way increase the existing rate of or
affect any fire insurance or other insurance which Landlord carries on the
Project or any of its contents, cause a cancellation or invalidation of any such
insurance or otherwise violate any Insurance Requirement. If the annual premiums
to be paid by Landlord with respect to any insurance obtained by Landlord
covering the Project or any of its contents shall be increased because either
the nature of Tenant's operations or the nature of Tenant's Trade Fixtures,
inventory, or leasehold improvements in the Premises may result in a hazardous
exposure, Tenant shall pay such increase upon demand by Landlord.

               (e)  All fire and extended coverage insurance policies carried by
either Landlord or Tenant shall provide for a waiver of rights of subrogation
against Landlord and Tenant on the part of the applicable insurance carrier
unless either (i) such waiver is then prohibited by applicable Texas law or (ii)
such waiver would invalidate, nullify, or provide a defense to coverage under
any such insurance policy. As long as the waivers contemplated by this
Subsection are in effect, Landlord and Tenant each hereby waives any and all
rights of recovery, claims, actions, or causes of action against the other (and
their respective employees, agents, officers, or partners) for any loss or
damage which may occur to the Premises or the Project which is covered by valid
and collectible insurance policies and to the extent that such loss is actually
recovered under any such insurance policy. The failure of Tenant to take out or
maintain any insurance policy required under this Section 7.3 shall be a defense
to any claim asserted by Tenant against Landlord by reason of any loss sustained
by Tenant which would have been covered by any such required policy. The waivers
set forth in this Subsection shall be in addition to, but shall not be in
substitution for, any other waivers, indemnities, or limitation of liabilities
set forth in this Lease.

          Section 7.4.  Indemnity. Tenant shall not be liable to Landlord or to
                        ---------
the Landlord Related Parties for any injury to person or damage to property
caused by the gross negligence or willful misconduct of Landlord or the Landlord
Related Parties. Subject to the provisions of Section 9.14 below, Landlord shall
indemnify and hold Tenant and the Tenant Related Parties harmless from any
liability, loss, cost, claim, or expense (including attorneys' fees and
expenses, court costs, and costs of investigation) arising out of, or alleged to
have arisen out of, the gross negligence or willful misconduct of Landlord or
the Landlord Related Parties. Landlord and the other Protected Parties shall not
be liable to Tenant or to the Tenant Related Parties for any injury to person or
damage to property caused by the negligence or misconduct of Tenant or the
Tenant Related Parties, or arising out of any use of, or the conduct of any
business in the Premises or other portions of the Project, by Tenant or the
Tenant Related Parties. Tenant shall indemnify and hold Landlord and the other
Protected Parties harmless from any liability, loss, cost, claim, or expense
(including attorneys' fees and expenses, court costs, and costs of
investigation) to the extent arising out of, or alleged to have arisen out of,
the negligence or misconduct of Tenant or the Tenant Related Parties or out of
any use of, or conduct of any business in, the Premises or any other portion of
the Project by Tenant or the Tenant Related Parties. The indemnifications
granted by both Landlord and Tenant in this Section 7.4 are subject to any
express limitations to the contrary in this Lease. "Landlord Related Parties"
means Landlord's officers, partners, employees, agents, and contractors.
"Protected Parties" means the Landlord Related Parties and, to the extent
applicable, the holder of any Financing

                                      24

<PAGE>

Lien, the lessor under any Ground Lease, and the management company for the
Building (and their respective directors, partners, officers, employees, and
agents).

          Section 7.5.  Damages from Certain Causes. Except to the extent caused
                        ---------------------------
by that Protected Party, none of the Protected Parties shall ever be liable or
responsible to Tenant, or any person claiming through Tenant, for any loss,
injury to person, or damage to property in, upon, or about the Premises or any
other portion of the Project resulting from (a) theft, fire, casualty,
vandalism, acts of God, public enemy, injunction, riot, strike, inability to
procure materials, insurrection, war, court order, requisition, or order of any
governmental body or authority; (b) the acts or omissions of other tenants of
the Project; (c) any other causes beyond Landlord's control; or (d) any damage
or inconvenience which may arise through repair or alteration of the Project.
All goods, property, or personal effects stored or placed by Tenant in or about
the Project shall be at the sole risk of Tenant.

                                   ARTICLE 8

                             DEFAULT AND REMEDIES

          Section 8.1.  Default by Tenant. The occurrence of any of the
                        -----------------
following events and the expiration of any grace periods hereafter described
shall constitute a default by Tenant under this Lease:

               (a)  The failure of Tenant to pay any Rent within ten (10) days
after Tenant's receipt of Landlord's written notice of such failure to pay;
provided Landlord shall be required to give such notice only twice in any twelve
(12) month period and thereafter Tenant shall be in default if any such payment
is not received when due and without notice;

               (b)  Tenant assigns its interest in this Lease or sublets any
portion of the Premises except as permitted in this Lease or Tenant otherwise
breaches the provisions of Section 6.2 of this Lease;

               (c)  Tenant uses the Premises for any purpose other than the
Permitted Use or otherwise breaches Tenant's operational covenants under
Sections 2.3, or 6.8 of this Lease after five (5) days Landlord's written notice
of such breach;

               (d)  Tenant breaches or fails to comply with any term, provision,
covenant, or condition of this Lease (other than as described in Subsections
[a], [b], or [c] above), or with any of the Building Rules now or subsequently
established, and such breach or failure continues for thirty (30) calendar days
after written notice by Landlord to Tenant or, if such condition cannot
reasonably be cured within such thirty (30) day period, Tenant shall fail to
commence such cure within such thirty (30) day period, or having commenced such
cure within such period shall thereafter diligently and continuously fail to
prosecute such cure to completion within sixty (60) days from the date of
Landlord's notice of such default;

               (e)  If the interest of Tenant under this Lease is levied on
under execution or other legal process, or if any petition in bankruptcy or
other insolvency proceedings is filed by or against Tenant, or any petition is
filed or other action taken to declare Tenant as bankrupt or to delay, reduces
or modify Tenant's debts or obligations or to reorganize or modify

                                      25

<PAGE>

Tenant's capital structure or indebtedness or to appoint a trustee, receiver or
liquidator of Tenant or of any property of Tenant, or any proceedings or other
action is commenced or taken by a governmental authority for the dissolution or
liquidation of Tenant (provided that no such levy, execution, legal process; or
petition filed against Tenant shall constitute a breach of this Lease if Tenant
shall vigorously contest the same by appropriate proceedings and shall remove or
vacate the same within thirty (30) calendar days from the date of its creation,
service, or filing);

               (f)  Tenant becomes insolvent, makes an assignment for the
benefit of creditors, or makes a transfer in fraud of creditors; or a receiver
or trustee is appointed for Tenant or any of its properties;

               (g)  Tenant abandons the Premises during the Lease Term; or

               (h)  If Tenant is an individual person, the death or legal
incapacity of Tenant; if Tenant is a corporation, Tenant ceases to exist as a
corporation in good standing in the state of its incorporation and/or ceases to
be duly authorized to transact business within the State of Texas; or if Tenant
is a partnership or other entity, Tenant is dissolved or otherwise liquidated.

          Section 8.2.  Landlord's Remedies. Upon the occurrence of any default
                        -------------------
by Tenant under this Lease, Landlord, at Landlord's sole option, may exercise
any one or more of the following described remedies, in addition to all other
rights and remedies provided at law or in equity:

               (a)  Landlord may at any time thereafter (without being under any
obligation to do so) re-enter the Premises and correct or repair any condition
which shall constitute a failure on the part of Tenant to observe, perform, or
satisfy any term, condition, covenant, agreement, or obligation of Tenant under
this Lease; and Tenant shall fully reimburse and compensate Landlord on demand
for the costs incurred by Landlord in doing so, plus profit and overhead in any
amount equal to fifteen percent (15%) of such cost. No action taken by Landlord
under this subsection shall relieve Tenant from any of Tenant's obligations
under this Lease or from any consequences or liabilities arising from the
failure of Tenant to perform such obligations.

               (b)  Landlord may terminate this Lease and repossess the
Premises. In the event that Landlord elects to terminate this Lease, Landlord
shall be entitled to recover damages equal to the total of (i) the cost of
recovering the Premises (including attorneys' fees and costs); (ii) the cost of
removing and storing Tenant's or any other occupant's property; (iii) the unpaid
Rent owed at the time of termination, plus interest thereon from the date when
due at the maximum rate of interest then allowed by law; (iv) the cost of
reletting the Premises (as reasonably estimated by Landlord and including
alterations or repairs to the Premises and brokerage commissions); (v) the costs
of collecting any sum due to Landlord (including without limitation, attorneys'
fees and costs); and (vi) any other sum of money or damages owed by Tenant to
Landlord as a result of the default by Tenant, whether under this Lease, at law,
or in equity.

               (c)  Landlord may terminate Tenant's right of possession of the
Premises without terminating this Lease and repossess the Premises. In the event
that Landlord

                                      26

<PAGE>

elects to take possession of the Premises without terminating this Lease, Tenant
shall remain liable for, and shall pay to Landlord, from time to time on demand,
(i) all costs and damages described in Subsection (ii) of this Section 8.2 and
(b) any deficiency between the total Rent due under this Lease for the remainder
of the Lease Term and rents, if any, which Landlord is able to collect from
another tenant for the Premises during the remainder of the Lease Term ("Rental
Deficiency"). Landlord may file suit to recover any sums falling due under the
terms of this Lease from time to time, and no delivery to or recovery by
Landlord of any portion of the sums owed to Landlord by Tenant under this Lease
shall be a defense in any action to recover any amount not previously reduced to
judgment in favor of Landlord. Landlord may use reasonable efforts to relet the
Premises on such terms and conditions and to such parties as Landlord, in
Landlord's sole discretion, may determine (including a term different from the
Lease Term, rental concessions, and alterations and improvements to the
Premises); but Landlord shall never be obligated to relet the Premises before
leasing other rentable areas within the Project, it being the intent of the
parties that Tenant shall not be placed in a preferential position by reason of
Tenant's own default. Any sums received by Landlord through reletting shall
reduce the sums owing by Tenant to Landlord, but Tenant shall not be entitled to
any excess of any sums obtained by reletting over and above the Rent provided in
this Lease under any circumstances. For the purpose of such reletting, Landlord
is authorized to decorate or to make any repairs, changes, alterations, or
additions in and to the Premises that Landlord may deem necessary or advisable.
No reletting shall be construed as an election on the part of Landlord to
terminate this Lease unless a written notice of such intention is given to
Tenant by Landlord. Notwithstanding any such reletting without termination,
Landlord may, at any time thereafter, elect to terminate this Lease for such
previous default. In the alternative (but only in the event that Tenant's
default constitutes a material breach), Landlord may elect to terminate Tenant's
right to possession of the Premises and to immediately recover as damages, in
lieu of the Rental Deficiency, a sum equal to the difference between (a) the
total Rent due under this Lease for the remainder of the Lease Term and (b) the
then fair market rental value of the Premises during such period, discounted to
present value using a discount rate of eight percent (8%) per annum ("Discounted
Future Rent"). In such event, Landlord shall have no obligation to relet the
Premises or to apply any rentals received by Landlord as a result of any
reletting to Tenant's obligations under this Lease; and the aggregate amount of
all damages due to Landlord, including the Discounted Future Rent, shall be
immediately due and payable to Landlord upon demand.

               (d)  In the event that Landlord elects to re-enter or take
possession of the Premises after Tenant's default, Tenant hereby waives notice
of such re-entry or re-possession and of Landlord's intent to re-enter or retake
possession. Landlord may, without prejudice to any other remedy which Landlord
may have for possession or arrearages in or future Rent, expel or remove Tenant
or any other person who may be occupying the Premises. Landlord may also change
or alter the locks or other security devices on the doors to the Premises
and/or, if applicable, remove Tenant's access media from the security system;
and Tenant waives, to the fullest extent allowed by law, any requirement that
notice be posted on the Premises as to the location of a key to such new locks
and any rights to obtain such a key.

               (e)  If Tenant abandons the Premises, Landlord may remove and
store any property of Tenant that remains within the Project at Tenant's
expense. In addition to Landlord's other rights and remedies, Landlord may
dispose of the stored property if Tenant does not claim that property within ten
(10) days after the date on which that property is first

                                      27

<PAGE>

stored by Landlord. Landlord shall deliver by certified mail to Tenant, at
Tenant's last known address, a notice stating that Landlord will dispose of
Tenant's property if Tenant does not claim such property within ten (10) days
after the date the property was first seized and stored by Landlord. In
addition, Tenant shall be liable to Landlord for all costs and expenses incurred
by Landlord in moving, storing, and disposing of the abandoned property and
shall indemnify and hold harmless Landlord from and against any and all loss,
damage, costs, expenses, and liability related to or in connection with such
removal, storage, and disposal of Tenant's property after abandonment.

               (f)  In the event that Rent is to be increased at various
intervals during the Lease Term, then Landlord may, at Landlord's sole election,
calculate the amount of unpaid Rents owed at the time of termination of this
Lease or calculate the amount of any Rental Deficiency or Discounted Future Rent
based upon the difference between the average rate of Rent payable by Tenant
over the entire Lease Term instead of on the amount of Rent payable by Tenant
during the applicable period. If Landlord agreed to allow Tenant to pay a lower
rate of rent during the earlier portions of the Lease Term and to then increase
the Rent at various stages during the Lease Term, Tenant acknowledges and agrees
that (i) such agreement was made as an accommodation to Tenant and in reliance
upon Tenant performing all of Tenant's obligations and paying Rent throughout
the entire Lease Term and (ii) such method of calculation is intended to provide
Landlord with the benefit of Landlord's bargain in this Lease.

               (g)  No termination of this Lease shall ever be deemed to have
occurred unless Landlord specifically notifies Tenant in writing that Landlord
has elected to terminate this Lease. No election of Landlord to re-enter the
Premises or to retake possession of the Premises shall ever be deemed or
construed to be a termination of this Lease.

               (h)  The provisions of this Section 8.2 shall override and
control over any conflicting provisions of Section 93.002 of the Texas Property
Code (as amended), and Tenant expressly waives any and all rights Tenant may
have under Section 93.002.

               (i)  Tenant hereby expressly waives notice of any default for
which notice is not specifically required under Section 8.1.

               (j)  All rights and remedies of Landlord under this Lease shall
be non-exclusive and shall be in addition to an cumulative of all other rights
or remedies available to Landlord under this Lease or by law or in equity.

          Section 8.3.  Landlord's Lien.  Intentionally deleted.
                        ---------------

          Section 8.4.  Attorney's Fees and Other Expenses of Enforcement. In
                        -------------------------------------------------
the event Tenant defaults in the performance or observance of any of the terms,
covenants, agreements, or conditions contained in this Lease, Tenant, to the
extent permitted by applicable law, shall pay to Landlord (a) all reasonable
expenses incurred by Landlord in collecting any sums due under, or enforcing any
of the terms of, this Lease; and (b) if Landlord places the enforcement of all
or any part of this Lease in the hands of an attorney, all attorneys' fees and
other costs of collection and enforcement incurred by Landlord.

                                      28

<PAGE>

          Section 8.5. Default by Landlord. Landlord shall be in default under
                       -------------------
this Lease in the event Landlord has not begun and pursued with reasonable
diligence the cure of any failure of Landlord to meet its obligations under this
Lease within thirty (30) days of the receipt by Landlord of written notice from
Tenant of Landlord's alleged failure to perform. In no event shall Tenant have
the right to terminate or rescind this Lease as a result of Landlord's default.
Tenant waives such remedies of termination and rescission and agrees that
Tenant's remedies for default under this Lease and for breach of any promise or
inducement are limited to a suit for damages and/or injunction. In addition,
Tenant shall, prior to the exercise of any such remedies, provide each holder of
a Financing Lien and each lessor under a Ground Lease with written notice and a
reasonable time to cure any default by Landlord.

                                   ARTICLE 9

                           MISCELLANEOUS PROVISIONS

          Section 9.1.  Amendments. This Lease may not be altered, changed, or
                        ----------
amended except by an instrument in writing signed by both Landlord and Tenant.

          Section 9.2.  Non-Waiver. No course of dealing between Landlord and
                        ----------
Tenant or any other person, nor any delay on the part of Landlord in exercising
any rights under this Lease, nor any failure to enforce any provision of this
Lease, nor the acceptance of any Rent by Landlord shall operate as a waiver or a
modification of the terms of this Lease or of any right which Landlord has to
demand strict compliance by Tenant with the terms of this Lease. If Landlord or
Tenant waives any agreement, condition, or provision of this Lease, such waiver
must be expressly set forth in a writing signed by either party and shall not be
deemed a waiver of any subsequent breach of the same or any other agreement,
condition, or provision contained in this Lease.

          Section 9.3.  Holding Over. In the event Tenant remains in possession
                        ------------
of the Premises after the expiration or termination of this Lease without the
consent of Landlord, Tenant shall be deemed to be occupying the Premises as a
tenant at will and shall pay Rent for each month (or partial month) during the
first thirty (30) days any such holdover period at a rate equal to 125% of the
Rent which Tenant was obligated to pay for the month immediately preceding the
end of the Lease Term and 200% of the amount of such Rent thereafter. No holding
over by Tenant after the expiration or termination of this Lease shall be
construed to extend the Lease Term or in any other manner be construed as
permission by Landlord to holdover. Additionally, in the event of any
unauthorized holding over by Tenant, Tenant shall indemnify Landlord against all
claims for any damages by any other person or entity to whom Landlord may have
leased all or any part of the Premises and for any other loss, cost, damage, or
expense (including attorneys' fees and costs of suit) incurred by Landlord as a
result of such holding over.

          Section 9.4.  Notices. Any notice, demand, consent, approval, request,
                        -------
or other communication required or permitted to be given pursuant to this Lease
(including any Exhibit to this Lease) or by applicable law shall be in writing
and shall be delivered by registered or certified mail, postage prepaid, return
receipt requested, telegram, facsimile, or expedited delivery service with proof
of delivery, addressed to Landlord or Tenant, as applicable, at the
<PAGE>

address for each specified in the first paragraph of this Lease. Any such
communication transmitted by telegram, facsimile, or personal delivery shall be
deemed to have been delivered as of the date actually received by the addressee.
Any such communication transmitted by registered or certified mail shall be
deemed to have been given or served on the third (3rd) business day following
the date on which such notice was deposited in a receptacle maintained by the
United States Postal Service for such purpose. Any notice of default from Tenant
to Landlord shall also be delivered to any holder of a Financing Lien or any
lessor under a Ground Lease who has notified Tenant of its interest and the
address to which notices are to be sent; and such notice shall not be effective
until delivered to such parties. Either Landlord or Tenant may, by ten (10)
days' prior notice to the other in accordance with this Section 9.4, designate a
different address or different addresses to which communications intended for
the party are to be sent.

          Section 9.5.  Independent Obligations. The obligations of Tenant under
                        -----------------------
this Lease are independent of Landlord's obligations, and Tenant shall not, for
any reason, withhold or reduce Tenant's required payments of Rent or fail to
fully perform Tenant's obligations under this Lease. In the event that Landlord
commences any proceedings against Tenant as a result of Tenant's default under
this Lease, Tenant will not interpose any counterclaim or other claim against
Landlord of whatever nature or description in any such proceedings. In the event
that Tenant attempts to interpose any such counterclaim or other claim against
Landlord in such proceedings, Landlord and Tenant stipulate and agree that such
counterclaim or other claim asserted by Tenant shall, upon motion by Landlord,
be severed out of the proceedings instituted by Landlord and that those
proceedings may proceed to final judgment separately and apart from, and without
consolidation with or reference to the status of, such counterclaim or other
claim asserted by Tenant.

          Section 9.6.  Survival. Neither the expiration or termination of the
                        --------
Lease Term pursuant to the provisions of this Lease, by operation of law, or
otherwise, nor any repossession of the Premises pursuant to any remedy granted
to Landlord under this Lease or otherwise shall ever relieve Tenant of Tenant's
liabilities and obligations under this Lease, all of which shall survive such
expiration, termination, or repossession.

          Section 9.7.  Other Tenants of Building. Neither this Lease nor
                        -------------------------
Tenant's continued occupancy of the Premises is conditioned upon either (a) the
opening of any showroom or business in the Building or in any portion of the
Project by any other person or entity or (b) the continued operations of any
such showroom or business.

          Section 9.8.  Name of Building and Project. Tenant shall not utilize
                        ----------------------------
the name of the Building or the Project for any purpose whatsoever, except to
identify the location of the Premises in Tenant's address. Landlord shall have
the right to change the name of the Building and/or the Project whenever
Landlord, in its sole discretion, deems it appropriate without any liability to
Tenant and without any consent of Tenant being necessary.

          Section 9.9.  Consent by Landlord. In each circumstance under this
                        -------------------
Lease in which the prior consent or permission of Landlord is required before
Tenant is authorized to take any particular type of action, the decision of
whether to grant or deny such consent or permission shall be within the sole and
exclusive judgment and discretion of Landlord unless otherwise
<PAGE>

specifically provided in this Lease with respect to that specific matter. Unless
(a) Landlord has specifically agreed otherwise in this Lease that Landlord will
not unreasonably withhold its consent with respect to that specific matter and
(b) Landlord then unreasonably withholds its consent with respect to that
specific matter, Tenant shall not have any claim for breach by Landlord or any
defense to performance of any covenant, duty, or obligation of Tenant under this
Lease on the basis that Landlord delayed or withheld the granting of such
consent or permission. Landlord's consent or approval to any particular act by
Tenant which requires such consent or approval shall not be deemed to waive or
render unnecessary consent to or approval of any subsequent similar act.

          Section 9.10.  Legal Interpretation. This Lease, and the rights and
                         --------------------
obligations of Landlord and Tenant under this Lease, shall be interpreted,
construed, and enforced in accordance with the laws of the State of Texas. All
obligations of the parties shall be performable in, and all legal actions to
enforce or construe this Lease shall be instituted in, the courts of, Dallas
County, Texas. All defined terms and other words used in this Lease shall
include the singular and plural, as applicable. References to the Premises, the
Building, the Land, or the Project shall also include any portion of each.
References to the Project shall include the Building and the Premises, and
references to the Building shall include the Premises. Words which are not used
as defined terms in this Lease shall be construed in accordance with the
meanings commonly ascribed to those words, relative to the context in which each
is used. The word "including" shall be construed as if followed, in each
instance, by the phrase "but not limited to." All article, section, and
subsection headings used in this Lease are for reference and identification
purposes only and are not intended to, and shall not under any circumstances,
alter, amend, amplify, vary, or limit the express provisions in this Lease. All
rights, powers, and remedies provided in this Lease may be exercised only to the
extent that their exercise does not violate any applicable law and are intended
to be limited to the extent necessary so that such provision will not render
this Lease invalid or unenforceable under applicable law. In the event that any
provision in this Lease, or the application of such provision to any person or
circumstance, shall be invalid or unenforceable to any extent, the remainder of
this Lease, or the application of such term or provision to persons or
circumstances other than those to which it is held invalid or unenforceable,
shall not be affected thereby. Landlord and Tenant hereby respectively
acknowledge that each such party has substantial experience in negotiation
commercial real estate leases, that this Lease is the product of extensive
negotiations between the parties, and that, therefore, neither Landlord nor
Tenant shall be charged with having promulgated this Lease and that no rule of
strict construction with respect to the provisions of this Lease shall be
applicable.

          Section 9.11.  Entire Agreement. Tenant agrees that (a) this Lease
                         ----------------
supersedes and cancels any and all previous statements, negotiations,
arrangements, brochures, agreements, and understandings, if any, between
Landlord and Tenant or displayed by Landlord to Tenant with respect of the
subject matter of this Lease, the Premises, the Building, or the Project and (b)
there are no representations, agreements or warranties (express or implied, oral
or written) between Landlord and Tenant with respect to the subject matter of
this Lease, the Premises, the Building, or the Project other than as set forth
in this Lease.

          Section 9.12.  Authority. Tenant represents and warrants that (a)
                         ---------
Tenant has the full right, power, and authority to enter into, and to perform
its obligations under, this Lease, and
<PAGE>

(b) upon execution of this Lease by Tenant, this Lease shall constitute a valid
and legally binding obligation of Tenant. If Tenant signs as a corporation, each
of the persons executing this Lease on behalf of Tenant covenant and warrant
that Tenant is a duly and validly existing corporation, that the execution of
this Lease by such persons on behalf of Tenant has been duly authorized by all
necessary corporate action, and that Tenant is qualified to do business in the
State of Texas. Likewise, Landlord represents and warrants that Landlord has the
full right, power, and authority to enter into, and to perform its obligations
under, this Lease, and that, upon execution of this Lease by Landlord, this
Lease shall constitute a valid and legally binding obligation of Landlord.

          Section 9.13.  Taxes on Tenant's Property. Tenant shall be liable for
                         --------------------------
all taxes levied against Tenant's Trade Fixtures, inventory, leasehold
improvements, and any other property of Tenant in the Premises or the Project.
If any such taxes are ever assessed against Landlord or Landlord's property and
Landlord elects to pay the same or if the assessed value of Landlord's property
is increased by the inclusion of Tenant's property, Tenant shall pay to
Landlord, within fifteen (15) days of demand, that part of such taxes
attributable to Tenant's property as additional Rent. Landlord shall be
responsible for paying all real property taxes levied against the Project.
However, if any alteration, addition, or improvement shall be made by Tenant
which causes an increase in the real property taxes, assessments, or other
governmental charges levied against the Building, Tenant shall pay to Landlord,
     within fifteen (15) days of demand, the amount of any such increase as
additional Rent.

          Section 9.14.  Landlord's Liability. Notwithstanding anything to the
                         --------------------
contrary set forth in this Lease, Tenant agrees that no personal, partnership,
or corporate liability of any kind or character whatsoever shall attach to
Landlord or its partners or venturers for payment of any amounts payable under
this Lease or for the performance of any obligation under this Lease. The
exclusive remedies of Tenant for the failure of Landlord to perform any of
Landlord's obligations under this Lease shall be to proceed against the interest
of Landlord in and to the Project. Landlord shall not be responsible in any way
to Tenant or any Tenant Related Party for any loss of property from the Premises
or public areas of the Building or for any damages to any property from any
cause whatever. Nor shall Landlord be responsible for lost or stolen personal
property, money, or jewelry from the Premises, regardless of whether such loss
occurs when the Premises are locked. Landlord shall never be liable for
consequential or special damages.

          Section 9.15.  Time of the Essence. In all instances in which Tenant
                         -------------------
or Landlord is required to pay any sum or do any act at a particular time or
within a particular period, it is understood that time is of the essence.

          Section 9.16.  Instruments and Evidence Required to be Submitted to
                         ----------------------------------------------------
Landlord. Each written instrument and all evidence of the existence or non-
--------
existence of any circumstances or conditions which is required by this Lease to
be furnished to Landlord shall in all respects be in form and substance
satisfactory to Landlord, and the duty to furnish such written instrument or
evidence shall not be considered satisfied until Landlord shall have
acknowledged that Landlord is satisfied with the form and content of each.

          Section 9.17.  Counterparts. This Lease may be executed in any number
                         ------------
of counterparts, each of which, when executed and delivered, shall be an
original; but such counterparts shall together constitute one and the same
instrument.
<PAGE>

          Section 9.18.  Recordation. Tenant shall not record (a) this Lease,
                         -----------
(b) any instrument to which this Lease may now or hereafter be attached, or (c)
any memorandum of this Lease.

          Section 9.19.  Effective Date. The submission of this Lease to Tenant
                         --------------
for examination does not constitute a reservation of or offer or option for the
Premises, and this Lease shall become effective only upon execution by both
Landlord and Tenant. The term "Effective Date" shall mean the date on which this
Lease is first fully executed by both Landlord and Tenant.

          Section 9.20.  Successors and Assigns. From and after the Effective
                         ----------------------
Date, this Lease shall be binding upon, inure to the benefit of, and be
enforceable by the parties to this Lease and their respective successors and
assigns (subject to the provisions of this Lease). As used in this Lease, the
phrase "successors and assigns" is used in its broadest possible context and
includes, without limitation and as applicable, the respective heirs, personal
representatives, successors, and assigns of each of the parties to this Lease
and any person, partnership, corporation, or other entity succeeding to any
interest in this Lease, the Premises, the Building, or the Project. Nothing
contained in this Section 9.20 nor in the definition of Tenant Related Parties
shall serve to alter or vary the provisions of Section 6.2 prohibiting the types
of transfers by Tenant described in that Section.

          Section 9.21.  Joint and Several Liability. If there is more than one
                         ---------------------------
party executing this Lease as Tenant, or if Tenant is a partnership, Tenant's
obligations under this Lease shall be the joint and several obligations of all
such parties executing as Tenant or all such partners constituting Tenant (as
applicable).

          Section 9.22.  Exhibits. The following Exhibits (and, if applicable,
                         --------
addenda, riders, or other attachments to this Lease) are attached, to and
incorporated in, this Lease for all purposes.

          Exhibit "A"  Property Description
          Exhibit "B"  Floor Plan
          Exhibit "C"  Rules and Regulations
          Exhibit "D"  Tenant Equipment License
          Exhibit "E"  Renewal Options
          Exhibit "F"  Subordination, Attornment and Non-Disturbance Agreement
          Exhibit "G"  Parking
          Exhibit "H"  Work Letter

          IN WITNESS WHEREOF, the parties hereto have executed this Lease as of
the Effective Date.

                                 LANDLORD:

                                 NEXCOMM ASSET ACQUISITION I, LP
                                 a Texas limited partnership
<PAGE>

                                 By: NEXCOM GP I, Inc., a Texas
                                     corporation and general partner

                                 By: /s/ Phillip J. Wise
                                    ---------------------------------------
                                 Name:  Philip J. Wise
                                 Title: President

                                 TENANT:

                                 EQUINIX, INC., a Delaware corporation

                                 By: /s/ [signature illegible]
                                    ---------------------------------------
                                 Name:_____________________________________
                                 Title:____________________________________
<PAGE>

                                  EXHIBIT "A"
                                  -----------

To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord,
                         and EQUINIX, INC., as Tenant

                             PROPERTY DESCRIPTION
                             --------------------

BEING a [*] acre tract of land situated in the City of Dallas, Dallas County,
Texas and out of the James A. Sylvester Survey, Abstract No. [*] and being a
part of City of Dallas Block No. [*], also being the same tract of land conveyed
to Dallas Market Center Company by a Special Warranty Deed recorded in Volume
[*], Page [*] of the Deed Records of Dallas County, Texas, said [*] acre tract
of land being more particularly described as follows:

BEGINNING at a 1/2 inch iron rod found for the point of intersection of the
southwesterly right-of-way line of the [*] with the northwesterly right-of-way
line of [*];

THENCE with the northwesterly right-of-way line of [*] the following:

     South 31 31'40" West a distance of 366.74 feet to an "X" chiseled in
     concrete found for corner in a curve to the right, the radius point of said
     curve bearing North 50 08'58" West a distance of 241.00 feet from said "X";

     Southwesterly with said curve to the right through a central angle of 03
     09'20" an arc distance of 13.27 feet to an "X" chiseled in concrete set for
     the point of reverse curvature of a curve to the left having a radius of
     259.00 feet;

     Southwesterly with said curve to the left through a central angle of 11
     28'43" an arc distance of 51.89 feet to a 1/2 inch iron rod found for the
     point of reverse curvature of a curve to the right having radius of 129.00
     feet;

     Southwesterly with said curve to the right through a central angle of 24
     06'22" an arc distance of 138.22 feet to a 1/2 inch iron rod set for the
     point of compound curvature of a curve to the right having a radius of
     50.00 feet;

     Northwesterly with said curve to the right through a central angle of 24
     06'22" an arc distance of 21.04 feet to a 1/2 inch iron rod found in the
     northeasterly right-of-way line of [*] for the point of compound curvature
     of a curve to the right having a radius of 1130.92 feet;

     THENCE with the northeasterly right-of-way line of [*] the following:

     Northwesterly with said curve to the right through a central angle of 07
     24'40" an arc distance of 146.28 feet to a 1/2 inch iron rod found for the
     point of tangency of said curve;

     North 55 33'45" West a distance of 816.18 feet to a 1/2 inch iron rod found
     for point of curvature of a curve to the left having a radius of 3289.04
     feet;

*CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                      E-1
<PAGE>

     Northwesterly with said curve to the left through a central angle of 01
     23'21" an arc distance of 79.74 feet to a bolt in concrete found for the
     most southerly corner of a tract of land leased to [*] from [*]as recorded
     in Volume [*], Page [*] of the Deed Records of Dallas County, Texas;

THENCE departing the northerly right-of-way line of [*] with the easterly line
of the [*] tract, North 09 21'30" East a distance of 1064.46 feet to a 1/2 inch
iron rod found for corner in the curving southwesterly right-of-way line of the
[*], the radius point of said curve being situated South 33 11'48" West a
distance of 1599.88 feet;

THENCE with the southerly right-of-way lien of the [*] the following:

     Southeasterly with said curve to the right through a central angle of 02
     41'48" an arc distance of 75.30 feet to a 1/2 inch iron rod found for
     corner;

     North 52 07'00" East a distance of 30.11 feet to a 1/2 inch iron rod found
     for corner in a curve to the right, the radius point of said curve being
     situated South 32 19'18" West a distance of 1553.95 feet;

     Northwesterly with said curve to the right through a central angle of 21
     26'39" an arc distance of 581.59 feet to a 1/2 inch iron rod set for
     corner;

     North 45 16'10" East a distance of 53.07 feet to 1/2 inch iron rod set for
     corner;

     South 31 48'40" East a distance of 976.20 feet to the POINT OF BEGINNING;

CONTAINING an area of 25.454 acres of land.

--------------------------------------------------------------------------------
                                   INITIALS
Landlord ________________                                      Tenant
--------------------------------------------------------------------------------

*CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                      E-2
<PAGE>

                                  EXHIBIT "B"
                                  -----------

To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord,
                         and EQUINIX, INC., as Tenant

                                  FLOOR PLAN
                                  ----------
                       (For Illustrative purposes only)

--------------------------------------------------------------------------------
                                   INITIALS
Landlord ________________                                      Tenant
--------------------------------------------------------------------------------

                                      E-3
<PAGE>

                                  EXHIBIT "C"
                                  -----------

To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord,
                          and EQUINIX, INC., as Tenant

                             RULES AND REGULATIONS
                             ---------------------

1.   No additional locks shall be placed on the doors of the Leased Premises by
     Tenant, nor shall any existing locks be changed unless Landlord is
     immediately furnished with two keys thereto. Landlord will without charge
     furnish Tenant with two keys for each lock existing upon the entrance doors
     when Tenant assumes possession with the understanding that at the
     termination of the lease these keys shall be returned or paid for at five
     dollars ($5.00) each. A deposit of one dollar ($1.00) each shall be
     required for additional keys.

2.   Tenant shall not at any time display a "For Rent" sign upon the Building or
     the Leased Premises, or advertise the Leased Premises for rent.

3.   Safes and other unusually heavy objects shall be placed by Tenant only in
     such places as may be approved by Landlord. Any damage caused by
     overloading the floor or by taking in or removing any object from the
     Leased Premises or the Building shall be paid by Tenant.

4.   Windows facing on corridors shall at all times be wholly clear and
     uncovered (except for such signs as Landlord may approve) so that a full
     unobstructed view of the interior of the Leased Premises may be had from
     the corridors, unless otherwise approved in writing by Landlord.

5.   No vehicles or animals shall be brought into the Building, other than as
     required by handicapped persons.

6.   Tenant shall not make any changes in the pipes, ducts, or wiring serving
     the Leased Premises or add any additional pipes, ducts, or wiring without
     the prior written consent of Landlord, and any such changes or additions
     shall be made in such manner as Landlord may direct.

7.   No sign, tag, label, picture, advertisement, or notice (other than price
     tags of customary size used in marking samples) shall be displayed,
     distributed, inscribed, painted or affixed by Tenant on any part of the
     outside of the Building or of the Leased Premises without the prior written
     consent of the Landlord.

8.   In the event Landlord should advance upon the request, or for the account
     of the Tenant, any amount for labor, material, packing, shipping, postage,
     freight or express upon articles delivered to the Leased Premises or for
     the safety, care, and cleanliness of the Leased Premises, the amount so
     paid shall be regarded as additional rent and shall be due and payable
     forthwith to the Landlord from the Tenant.

                                      E-4
<PAGE>

9.   The corridors and hallways of the Building shall not be used by Tenant for
     any purpose other than ingress to or egress from the Leased Premises.

10.  Tenant shall not do or permit to be done within the Leased Premises
     anything which would unreasonably annoy or interfere with the rights of
     other tenants in the Building, or which might constitute a potential hazard
     to other tenants or visitors.

11.  During the thirty (30) days prior to the expiration of this Lease, Landlord
     may show the Leased Premises to prospective tenants.

12.  Tenant shall not put or operate any steam engine, boiler, industrial
     machinery or stove in the Building or upon the Leased Premises or do any
     cooking thereon or use or allow to be kept in the Building or upon the
     Leased Premises any explosives or any kerosene, camphene, bottled gas, oil
     or other highly flammable materials, except gas supplied through metal
     pipes for heating purposes and normal and customary cleaning and janitorial
     supplies to the extent permitted under applicable laws.

13.  Landlord reserves the right to prescribe reasonable qualifications for
     admission into the Building.

14.  Models, salespersons or other employees or representatives of Tenant, shall
     not model, demonstrate display, or show in any manner any merchandise
     outside of the Leased Premises in the Building or on the Property without
     Landlord's prior written consent.

15.  As a courtesy, but not as an obligation, Landlord may, at Landlord's
     option, upon request by Tenant, receive and store articles or merchandise
     delivered to Tenant at the Building; provided, however that such articles
     of merchandise are properly addressed and identified and all postage,
     handling and delivery charges are prepaid by Tenant. Landlord assumes no
     responsibility whatsoever for the loss, damage or destruction of such
     articles of merchandise received at the Building by Landlord on behalf of
     Tenant, and Tenant hereby waives all claims against Landlord for any damage
     or loss arising at any time from the loss, damage or destruction of such
     articles of merchandise. Tenant agrees to pay to Landlord as additional
     rent the amount of all storage, delivery, handling and other expenses
     incurred by Landlord as a result of the receipt and storage of such
     articles of merchandise.

16.  Canvassing, peddling, soliciting and distribution of handbills or any other
     written material in the Building or in the Building's parking areas are
     prohibited, and each tenant shall cooperate to prevent the same.

17.  If the Leased Premises front on the atrium within the Building, Tenant
     shall cause the Leased Premises to be kept open for business and occupied
     by Tenant's personnel during all normal business hours of the Building.

18.  These Rules and Regulations are in addition to, and shall not be construed
     to in any way modify or amend, in whole or in part, the terms, covenants,
     agreements and conditions of any lease of space in the Building.

                                      E-5
<PAGE>

19.  Landlord reserves the right to make such other and reasonable rules and
     regulations as in its judgment may from time to time be needed for the
     safety, care and cleanliness of the Building, and for the preservation of
     good order therein.

20.  Smoking is permitted within the Building only in areas so designated by
     Landlord. Smoking within the Leased Premises is at the discretion of
     Tenant, provided, however, that such smoke does not migrate into the
     Building's common areas, hallways, etc. or into another tenant's premises.
     Tenant hereby indemnifies Landlord from any and all claims resulting from
     Tenant's permitting of smoking within the Leased Premises. Landlord
     reserves the right to change areas where smoking is permitted and change
     these Regulations, including designating the Building as non-smoking.

21.  A visitor information directory system will be provided by Landlord to
     assist visitors in locating tenants.

22.  To the extent that meeting rooms are offered, a tenant's meeting room use
     will be coordinated on a reservation basis and all tenants will be
     eligible. Standard fees will be applied and Landlord will control the
     rental of these areas and the use of the areas will be coordinated by the
     buyer/tenant services department of Landlord. Reservations for meeting room
     space within the Building will be on a first-come first-served basis.

23.  If, and only if, the Tenant's permitted use allows the operation of a
     showroom, warehousing and onsite delivery to customers is prohibited in
     permanent showrooms and in exhibit space when used in conjunction with
     showrooms, payment for products or services that of a retail sales nature
     are prohibited (provided, however, payment or partial payment for orders
     taken at the Building for future delivery to a buyer will be allowed if it
     is within the applicable tenant's normal business practices and is not of a
     retail sales nature, it being the intention of this provision to permit
     payments or partial payments intended to bind an order for future delivery
     without in any way qualifying or circumventing the prohibition within the
     Building against retail sales).

24.  Landlord may amend these Rules and Regulations from time to time and such
              --- -----
     changes shall be binding upon Tenant.

 ------------------------------------------------------------------------------
                                   INITIALS
   Landlord___________________                                  Tenant
 ------------------------------------------------------------------------------
 ______________________
                                      E-6
<PAGE>

                                  EXHIBIT "D"
                                  -----------

 To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord
                          and EQUINIX, INC., as Tenant

                            TENANT EQUIPMENT LICENSE
                            ------------------------

This Exhibit "D" describes the licenses to install and operate certain specified
"Tenant Equipment" in the Building which is being granted by Landlord to Tenant
upon the following terms and conditions:

     1.   DEFINED TERMS. For purposes of this Exhibit, all terms defined in this
          -------------
Lease (including other exhibits to this Lease) will be used in this Exhibit
without further definition. In addition, when delineated with initial capital
letters, the following terms will have the following respective meanings:

     a)   "Antenna Equipment" means the satellite antenna, together with related
          wiring and equipment, or Tenant's Customer's equipment which are
          approved by Landlord pursuant to this Exhibit.
     b)   "Antenna Fee" means Zero Dollars ($0.00) per month.
     c)   "Building Grade" means the type, brand and/or quality of materials
          which Landlord designates from time to time to be the minimum quality
          to be used in the Building or the exclusive type, grade, or quality of
          material to be used in the Building.
     d)   "Cable" means only (i) optical fibers encased in an aluminum sleeve,
          (ii) EMT conduit, (iii) copper cable, or (iv) other materials approved
          by Landlord.  The Cable (or Conduit) shall not exceed four inches in
          diameter.
     e)   "Conduit" means a plastic or metal sleeve, no more than four (4)
          inches in aggregate diameter, unless a larger size is expressly
          approved by Landlord in writing, in which Cable is encased and/or
          through which Cable passes.
     f)   "Cooling Equipment" means dry cooling units, together with related
          wiring, piping, vents, and equipment, which are approved by Landlord
          pursuant to this Exhibit.
     g)   "Cooling Equipment Fee" means Zero Dollars ($0.00) per month.
     h)   "Generator" means generators with automatic transfer switches, 80db
          (max) sound/weather enclosure and load bank equipment.
     i)   "Generator Fee" for the initial Generator pad shall be waived.
          Additional pads may not be added without the prior approval of
          Landlord (which may be granted, denied, or conditioned in Landlord's
          sole discretion); and the size and location of each additional pad
          will be at Landlord's sole option.  The Generator Fee applicable to
          any additional pad will be at the then current Landlord's charge for
          each such additional pad.
     j)   "License Fees" means, collectively, the Antenna Fee, the Pathway Fee,
          the Cooling Equipment Fee, the Generator Fee,  and any other sums of
          money becoming due and payable to Landlord hereunder.

                                      E-7
<PAGE>

     k)   "License Term" means a term commencing on the Commencement Date and
          shall expire upon the expiration or earlier termination of the Lease
          Term, unless sooner terminated pursuant to the provisions of this
          Exhibit.
     l)   "Normal Business Hours" for the Building means 8:30 a.m. to 5:00 p.m.
          Mondays through Fridays, exclusive of normal business holidays.
     m)   "Pathway" means a riser, raceway, or other vertical and/or horizontal
          space or pathway within the Building of no more than four inches in
          diameter (unless a greater size is approved in writing by Landlord)
          used for routing telecommunications cables and ancillary equipment
          from Tenant's point of presence in the Building which has been
          designated by Landlord.  The precise location of the Pathways
          applicable to this Telecommunications License will be designated by
          Landlord and the Telecommunications Equipment (as defined herein) will
          be installed only as designated by Landlord.
     n)  "Pathway Fee" means the sum calculated for all installed Cable or
          Conduit from Tenant's point of presence to other locations or
          customers in the Building at the rates identified in Schedule 1 per
                                                               ----------
          month.
     o)   "Service Fee" means the sum calculated for all installed services from
          the Licensee's point of presence to other locations or customers in
          the Building at the rates identified in Schedule 2 per month during
                                                  ----------
          each month of the License Term.
     p)   "Tank" means the__________ gallon fossil fuel tank and associated
          transfer pumps, to be installed by Tenant at the location designated
          by Landlord.  The Tank must have self-contained spill control
          features, be installed in a secure and safe location above ground, and
          must conform to all Legal Requirements (defined in Paragraph 15 below)
          concerning tank tightness, spill control and monitoring features.
     q)   "Telecommunications Equipment" means the Cable, Conduit, junction
          boxes, hangers, pull boxes, grounding wiring, and related equipment
          used in the normal course of Tenant's business, which will be
          installed by Tenant, after approval by Landlord, into the designated
          Service Areas and Pathways to be used by Tenant, pursuant to the terms
          of this License.
     r)   "Tenant Equipment" means, individually, or collectively, as
          applicable, the Antenna Equipment, the Cooling Equipment, the
          Generator, the Telecommunications Equipment, and the Tank.
     s)   "Tenant Equipment Areas" means, individually or collectively, as
          applicable, the Pathways, Service Areas, and sites for the location of
          the Antenna Equipment, the Generator, the Cooling Equipment, and the
          Telecommunications Equipment designated by Landlord under this
          Exhibit.  The designated Service Areas and Pathways may also be used
          by Landlord and others, and Landlord's designation of these areas does
          not confer an exclusive right for Tenant to use those areas.
          ---
     2.   GRANT OF LICENSE.  Subject to and upon the terms set forth in this
          ----------------
Exhibit, Landlord grants the following licenses to Tenant:

          a)   TELECOMMUNICATIONS LICENSE.  A license to use the Pathways,
               --------------------------
     designated by Landlord and to install Cable in those designated Pathways
     which connects to various tenants of the Building on a non-exclusive basis
     ("Telecommunications License").  Landlord specifically reserves the right
     to contract with competitors of Tenant

                                      E-8
<PAGE>

     for the same or similar services in the Building and acknowledges that
     Landlord has entered into other such contracts prior to the date of this
     Telecommunications License. Landlord shall have no obligation to assist
     Tenant in marketing its equipment and/or services in the Building or to any
     other property owned by Landlord. In addition, Tenant shall have the right
     to install and use four (4) four-inch (4") conduits at no charge in the
     Pathways, in a location determined by Landlord and reasonably acceptable to
     Tenant, for the exclusive use of Tenant's telecommunication cabling to
     connect from a minimum point of entry into the Building to the Premises.

          b)   ANTENNA LICENSE.  A license to install, operate, maintain, and
               ---------------
     repair the Antenna Equipment located at a location designated by Landlord.
     The size of the pad shall not exceed 36' X 36',  and the location, and
     manner of installation of the Antenna Equipment shall be determined at
     Landlord's sole discretion, which discretion will take into consideration
     (a) the functional requirements of the Antenna Equipment and any other
     satellite antenna dishes located on the roof of the Building; (b) standards
     of architectural integrity with respect to the Building (and, in that
     regard, the Antenna Equipment shall be located so as to not be visible
     except from above the Building, shall match the Building colors, and shall
     have no visible marking or logo).  Tenant shall be permitted to install and
     test the equipment from and after the Commencement Date and prior to the
     Rent Commencement Date, subject to the terms hereof except that the
     obligation to pay the Antenna License Fee will not commence until the Rent
     Commencement Date.  With respect to the installation of the Antenna
     Equipment, the Antenna Equipment shall not be affixed by nail, bolt, screw
     or other device which penetrates the roof of the Building; and all wiring
     penetrations shall be subject to Landlord's prior approval and shall be
     made by Landlord's roofing contractor at Tenant's sole cost and expense.
     Notwithstanding anything to the contrary in this Paragraph, Landlord shall
     reserve, for the use of Tenant, space for two (2) four-inch (4") conduits
     or cabling from the Leased Premises to the roof of the Building at no
     charge to Tenant.

          c)   GENERATOR LICENSE.  A license to install, operate, maintain, and
               -----------------
     repair the Generators and the tanks at such location on the Property as is
     approved in writing by Landlord ("Generator License").  The Generator
     License includes the right for Tenant (i) to use such locations on the
     Property as are approved in writing by Landlord in order for Tenant to
     install the Generators cabling to, and core drilling of, the Building core
     structural wall (it being acknowledged that Landlord has made no
     representation to Tenant that Tenant will be able to utilize any existing
     utility easements in this regard), and (ii) to use such Pathways as are
     approved in writing by Landlord in order for Tenant to install its
     Generators cabling from the points of entry at the Building core structural
     wall to the Leased Premises.

          d)   COOLING EQUIPMENT LICENSE.  A license to install, operate,
               -------------------------
     maintain, repair, and replace the Cooling Equipment in an area outside the
     Building as outlined on the site plan attached hereto as Schedule 5.  The
                                                              ----------
     size, location, and manner of installation of the Cooling Equipment shall
     be approved by Landlord as a part of the approval of the Plans and
     Specifications pursuant to the Work Letter attached as Exhibit H to this
     Lease, which approval will take into consideration the functional
     requirements of the Cooling Equipment and of any other equipment located in
     the vicinity of the Cooling Equipment and shall be subject to standards of
     structural and architectural integrity with respect to the Building.  In
     that regard, the Cooling Equipment shall be

                                      E-9
<PAGE>

     located so as not to be visible from any public approach to the Building.
     The area to be covered by the Cooling Equipment, including necessary
     walkways and required air space, shall not exceed ______ square feet.
     Because of existing rights granted to other tenants and the location of the
     Service Areas within the Building, Tenant acknowledges that the most
     efficient, direct, or cost effective route for such Cooling Equipment may
     not be available.

For purposes hereof, the Telecommunications License, the Antenna License, the
Generator License and the Cooling Equipment License will sometimes be
collectively referred to as the "License" in this Exhibit.

     3.   LICENSE TERM.  This License shall be in effect during the License
          ------------
Term.  However, Tenant shall have the right to use and occupy the Tenant
Equipment Areas as provided hereunder from and after the Commencement Date for
the purpose of installing the Tenant Equipment.  If any Tenant Equipment Areas
are not available due to the omission, delay or default of Tenant, or anyone
acting under or for Tenant, the obligations of Tenant under this Exhibit,
including, without limitation, the obligation to pay License Fees shall
nonetheless commence as of the Commencement Date.  Prior to the expiration or
earlier termination of this License, unless Landlord otherwise agrees in writing
at the time of Landlord's giving of its approval for Tenant's installation or
thereafter during the Term, Tenant shall remove all of Tenant's Equipment that
can be removed without causing any material damage to the Building and shall
surrender and deliver the Tenant Equipment Areas to Landlord in the same
condition in which they existed at the Commencement Date, excepting only
ordinary wear and tear and damage arising from any cause not required to be
repaired by Tenant.  In the event that Tenant fails to comply with the terms of
this Paragraph 3, (i) all such Tenant's Equipment remaining within the Property
may, at Landlord's option, become the sole property of Landlord or (ii) Landlord
may, if it so elects, perform any act which Tenant is required to perform and/or
remove the Tenant's Equipment and other property at Tenant's cost, and Tenant
shall pay Landlord promptly all costs incurred in removing said property within
ten (10) Working Days of demand.

     4.   USE.  The Tenant Equipment Areas shall be used solely for the
          ---
installation, operation and maintenance of the Tenant Equipment and for no other
purpose whatsoever.  Any use of the Tenant Equipment Areas for any other purpose
or any attempt by Tenant to allow the use or occupation of the Tenant Equipment
Areas by anyone other than Tenant shall, unless otherwise agreed to by Landlord
in writing shall be a default; and Landlord shall have the right to immediately
terminate this License unless such default is not cured within five (5) Working
Days after notice thereof.  Tenant shall not use or permit the use of the Tenant
Equipment Areas for any purpose which is illegal, dangerous to life, limb or
property, or which, in Landlord's reasonable opinion, creates a nuisance or
which would increase the cost of insurance coverage with respect to the
Building.  In particular, no semiconductors or other electronic equipment
containing polychlorinated biphenyls (PCB's) or other environmentally hazardous
materials will either be used or stored in or around the Tenant Equipment Areas
except as otherwise specifically provided in this Paragraph; and no such
materials will be used in any of the Tenant Equipment installed by Tenant in the
Tenant Equipment Areas.  Notwithstanding the foregoing, Tenant may use and store
fossil fuels for its Generators and batteries for its emergency electrical
backup systems in its Premises, so long as Tenant does so in compliance with all
applicable Legal Requirements.  Tenant will not permit unauthorized persons or
persons with insufficient

                                     E-10
<PAGE>

expertise or experience to enter Service Areas to maintain or operate the Tenant
Equipment. Tenant understands that the mechanical rooms within these Service
Areas must be kept locked and secure at all times must not be available or open
to the public. Landlord may, at Landlord's discretion, authorize other licensees
and tenants of the Building to use portions of the designated Pathways or
Service Areas, or to use portions of other Pathway or Service Areas in the
Building, whether for the installation of telecommunications equipment or
otherwise, so long as such uses would not require Tenant to remove its
previously installed Cable from the designated Pathways or Telecommunications
Equipment from the designated Service Area. Tenant acknowledges that
interruptions in utility services are not uncommon in facilities such as the
Building and that any sensitive electronic equipment which may be used in the
Building should be protected by Tenant from utility service interruptions by the
use of backup power supplies, surge protectors, and other appropriate safety
systems.

     5.   INSTALLATION.  The point of presence and network interface will be in
          ------------
accordance with the rules and regulations established by the Public Utility
Commission or other governmental authority with jurisdiction over such matters
in the State of Texas.  The installation of the Tenant Equipment in the Tenant
Equipment Area) shall be at the sole cost and expense of Tenant. All Tenant
Equipment will be installed in a good and workmanlike manner, and the
installation must be approved by Landlord's technical representative prior to
the commencement of use of any Tenant Equipment by Tenant.

     6.   LICENSE FEE PAYMENT.
          -------------------

     a)   The License Fees for each calendar month or portion thereof during the
          License Term shall be due and payable in advance on the first day of
          each month during the License Term without any setoff or deduction
          whatsoever; and Tenant shall pay the License Fees monthly, in advance,
          on or before the first day of each calendar month, and without demand.
          All installments of the License Fees which are not paid within five
          (5) Working Days of the date when due will bear interest, and if not
          paid within five (5) Working Days' notice thereof shall be subject to
          a late charge of five percent (5%) of the amount then due, and be
          subject to the provisions of Section 8.1 of the Lease.

     b)   In addition to the License Fees, Tenant shall pay Landlord if, and
          when due, any sales, use or other taxes or assessments which are
          assessed or due by reason of this License hereunder.

     c)   Upon each anniversary date of the Commencement Date, including any
          renewal term, the License Fees payable by Tenant shall increase as
          follows and using the following definitions:

          i)   "Consumer Price Index" - The monthly indexes of the National
               Consumer Price Index for All Urban Consumers (CPI-U) - All Items,
               issued by the Bureau of Labor Statistics.

          ii)  "Base Price Index Number" - The Consumer Price Index as of
               December of the year in which the Commencement Date occurs.

                                     E-11
<PAGE>

          iii) "Current Index Number" - The Consumer Price Index as of December
               of the year in which the calculations are being done.

          iv)  If the Current Index Number is greater than the Base Price Index
               Number, then the "Percentage of Increase" shall be calculated as
               follows:

(Current Index Number - Base Price Index Number) / Base Price Index = Percentage
of Increase

          This Percentage of Increase shall be multiplied by the License Fees
          defined above to obtain the new rate to go into effect on each
          anniversary of the Commencement Date of this License.  This Percentage
          of Increase applies to License Fees only and does not apply to any
          charges in the Base Rent.

     d)   Tenant shall keep an accurate set of books and records of all
          installed service from and  business conducted by Tenant in the
          Building, and all supporting records such as book orders, and other
          records which are necessary to verify and substantiate the amount of
          Tenant's Pathway Fee and Service Fee, at Tenant's business office
          located in the Premises.  All such books and records shall be retained
          and preserved for at least twenty-four (24) months after the end of
          the calendar year to which they relate and shall be subject to
          inspection and audit by Landlord and its agents at all reasonable
          times.  The acceptance by Landlord of any payment of any License Fees
          shall be without prejudice to Landlord's right to examination of
          Tenant's books and records in order to verify the computation of the
          Service Fee or the Pathway Fee provided by Tenant.  In the event
          Landlord is not satisfied with any monthly statement or annual
          statement submitted by Tenant, Landlord shall have the right to have
          its auditors make a special audit of all books and records, where-ever
          located, pertaining to sales made in or from the Building during the
          period in question.  If such statements are found to be incorrect to
          an extent of more than two percent (2%) over the figure submitted by
          Tenant, Tenant shall pay for such audit.  Tenant shall promptly pay to
          Landlord any deficiency or Landlord shall promptly credit to Tenant
          any overpayment, as the case may be, which is established by such
          audit.

     7.   CONDITION OF THE TENANT EQUIPMENT AREA.  Tenant accepts the Tenant
          --------------------------------------
Equipment Area "as is" without benefit of any improvements to be constructed or
made by Landlord.

     8.   MAINTENANCE AND REPAIR BY LANDLORD.  Landlord shall maintain and
          ----------------------------------
repair the Pathways, the exterior and load-bearing walls of the Building, floors
of the mechanical rooms (but not floor coverings), and the roof of the Building,
which may be required from time to time, but only after such required repairs
have been requested by Tenant in writing.  In no event shall Landlord be
responsible for the maintenance or repair of improvements which are not composed
of Building Grade materials.

     9.   SERVICE AREA AND ROOF ACCESS.  Except in the case of an emergency,
          ----------------------------
Tenant shall not enter or attempt access to any of the Service Areas (including
air, electrical, mechanical or telecommunications risers, ducts, closets,
conduits, duct work, rooms or other

                                     E-12
<PAGE>

horizontal or vertical spaces in the Building) or attempt to obtain access to
the roof of the Building without notifying Landlord in writing at least two (2)
days in advance. In the case of an emergency, Tenant may enter or seek access to
the roof of the Building or to the Pathways through the Service Areas provided
Tenant gives Landlord at least two (2) hours prior notice and provided that a
Building security guard must unlock such Service Area or access door to the
roof. If Landlord is also experiencing an emergency situation in the Building at
the same time that Tenant has notified Landlord of an emergency, Landlord shall
have no obligation to first address or respond to Tenant's emergency and shall
only be obligated to accommodate Tenant's concerns promptly as time permits
thereafter. Tenant also agrees to furnish Landlord, within two (2) Working Days
thereafter, a written report explaining all repairs and procedures which were
conducted during any such emergency operations, in sufficient detail to permit
Landlord's engineers to evaluate same. Any access to the Service Areas or to the
roof shall require Tenant to sign in at the security department console, and
Tenant shall permit the Landlord's security guard or a representative of
Landlord to accompany Tenant during any such work within a Service Area or on
the roof, if Landlord so desires. Except in the case of an emergency, no
installation, alterations or repairs shall be initiated without first delivering
to Landlord's engineers plans and specifications of the proposed changes, in
substance and form acceptable to Landlord. As soon as reasonably practicable
after the occurrence of an emergency, plans and specification shall be submitted
to Landlord for approval with respect to those repairs or replacements. No oral
approval of these plans and specifications shall be effective. No electrical
grounding shall be permitted to other equipment in the mechanical rooms without
Landlord's specific written approval of the method and location of such
grounding. No monitoring or inspection of Tenant's work by Landlord's
representatives shall be deemed supervision of Tenant's employees or shall be
deemed to be a representation or warranty of any particular level of
telecommunications expertise attained by Landlord's representative. Tenant shall
monitor and supervise its own employees and shall assume responsibility for the
expertise and quality of its work and shall not rely upon Landlord for same.

     10.  NO ACCESS TO OTHER TENANTS' PREMISES.  Tenant acknowledges that
          ------------------------------------
nothing in this License entitles it to enter and connect the Tenant Equipment to
any tenant's premises in the Building without the prior written consent of
Landlord. Tenant also acknowledges that it has been informed that
telecommunications connections to individual tenant's premises in the Building
will normally require removal of ceiling panels, at each tenant's expense, with
such removal operations only being performable by Landlord's agents or
employees.

     11.  LICENSES AND PERMITS.  Prior to commencing any work in the Tenant
          --------------------
Equipment Area, Tenant shall obtain all necessary licenses, permits and consents
related to such installation activities and to  the operation and use of the
Tenant Equipment and provide copies of same to Landlord.  Landlord shall have
the right to monitor all such work, at its own expense.

     12.  COSTS.  Tenant shall be responsible for any and all cost, damage or
          -----
expense arising from the installation, maintenance, repair or operation of the
Tenant Equipment, including, without limitation, any and all cost, damage or
expense to the Building or the property of Landlord or other licensees or
tenants of the Building arising from such installation, maintenance, repair, or
operations.  Tenant will make any and all repairs necessary in a timely manner.
If Tenant does not make required repairs to Landlord's satisfaction within
twenty-four

                                     E-13
<PAGE>

(24) hours of notification from Landlord that said repairs are
necessary within a tenant's space or within ten (10) days of notification from
Landlord that said repairs are necessary pursuant to Paragraph 13 of this
Exhibit then Landlord will have the right but not the obligation to perform any
such repairs at Tenant's sole cost and expense.  Tenant shall on demand pay to
Landlord as additional License Fees (i) the cost of such work plus fifteen
percent (15%) thereof as administrative costs; plus (ii) interest thereon at the
rate of 12% per annum from the date of demand.

     13.  MAINTENANCE, REPAIRS, AND ALTERATIONS BY TENANT.  Tenant shall not
          -----------------------------------------------
commit any waste or allow any waste to be committed within or on any portion of
the Tenant Equipment Areas or in any Service Area and will maintain Tenant's
installations in the Tenant Equipment Areas in a clean, attractive condition and
in good repair.  Tenant will remove all excess cable, tools, and equipment and
will keep all areas neat and clean at all times.  Provided Tenant fails to do so
after ten (10) Working Days notice given by Landlord to Tenant, Landlord shall
have the right, at its option, but at Tenant's cost and expense, to repair or
replace any damage done to the Building, or any part thereof, caused by Tenant
(or by any  contractor, agent, or employee of Tenant); and Tenant shall pay the
reasonable cost thereof (net of any applicable insurance proceeds) to Landlord
within ten (10) Working Days of demand as additional License Fees.  Tenant shall
not make or allow any alterations to such Tenant Equipment Areas materially
affecting mechanical, electrical, plumbing, or other basic systems within the
Building, its structure, or its operations without the prior written consent of
Landlord.  Tenant shall not place signs on any of the doors or corridors leading
to the Tenant Equipment Areas, without first obtaining the prior written consent
of Landlord in each such instance, which consent may be given or arbitrarily
withheld on such conditions as Landlord may elect.  Landlord shall have the
right, at its option, at Tenant's own cost and expense, to remove any signs
placed by Tenant without Landlord's prior written consent, and to repair any
damage caused by the such signs.  Except as provided in Section 5.4 of this
Lease with respect to Tenant's Trade Fixtures, any and all alterations to the
Tenant Equipment Areas shall become the property of Landlord upon termination of
this License.

     14.  USE OF ELECTRICAL SERVICES BY TENANT.  All electrical usage associated
          ------------------------------------
with the Tenant Equipment will be governed by the provisions of Section 2.5 of
the Lease.

     15.  LAWS, REGULATIONS, AND INTERFERENCE.  Tenant, at Tenant's sole cost,
          -----------------------------------
shall (a) comply with all Legal Requirements and Insurance Requirements
applicable to Tenant's use and occupancy of the Building (including, without
limitation, the installation, maintenance, repair, or operation of Tenant
Equipment), and (b) take all measures necessary to assure that the Tenant
Equipment strictly complies with all applicable Legal Requirements and Insurance
Requirements.  Tenant shall also pay promptly when due all royalties or other
fees due in connection with the operation of the Tenant Equipment.  In the event
compliance with this paragraph shall require modifications or alterations of the
Tenant Equipment or the Tenant Equipment Areas, no modification or alteration
shall be made without Landlord's prior written consent, which consent may be
withheld in Landlord's sole judgment or granted on such terms and conditions as
Landlord may determine in its sole judgment.  Tenant shall take all measures
necessary to assure that the Tenant Equipment does not interfere with or disturb
the operation of any other equipment or business of Landlord or of any other
licensee, tenant, or occupant of the

                                     E-14
<PAGE>

Building. Tenant shall modify the Tenant Equipment or relocate the Tenant
Equipment to another area approved by Landlord in the event that the Tenant
Equipment, in Landlord's sole judgment, causes any interference with or disturbs
the operation of any other equipment or business of Landlord or of any other
occupants or licensees of the Building or creates or results in any unreasonable
noise, odor, or nuisance to any other occupants of the Building, or areas
adjacent to the Building. Tenant must immediately shut off the relevant Tenant
Equipment upon notification of interference with other installations or
activities and may restart, modify, or relocate that Tenant Equipment to test
for interference only with Landlord's permission. "Insurance Requirements" means
all terms and any insurance policy obtained by Landlord or Tenant covering or
applicable to the Property, the Leased Premises, or the Tenant Equipment Area,
all requirements for the issuing of each such insurance policy; and all orders,
rules, regulations, and other requirements of the National Board of Fire
Underwriters (or any other bodies exercising any similar functions) which are
applicable to the Building, the Property or any use or condition of the Building
or the Property. "Legal Requirements" shall mean all laws, statutes, codes,
acts, ordinances, orders, judgments, decrees, injunctions, rules, regulations,
permits, licenses, authorizations, and requirements of all governmental
authorities foreseen or unforeseen which now or at any time hereafter may be
applicable to the Building or the Property, including, without limitation, the
Americans with Disabilities Act, all federal, state, and local laws regulations
and ordinances pertaining to air and water quality, hazardous materials, waste
disposal, and other environmental matters, and all laws, codes, and regulations
pertaining to zoning, land use, health, or safety.

     16.  SITE TECHNICAL STANDARDS.  Tenant will strictly comply with the Site
          ------------------------
Technical Standards (Schedule 4) as adopted and altered by Landlord from time to
                     ----------
time and will cause all of the Tenant Related Parties to do so.  All changes to
such standards will be sent by Landlord to Tenant in writing.  "Tenant Related
Party" means Tenant's officers, partners, employees, agents, contractors,
licensees, concessionaires, customers, and invitees.

     17.  ENTRY BY LANDLORD.  Landlord and the Landlord-Related Parties shall
          -----------------
have access to the Tenant Equipment Areas at all times to inspect the same,
clean the same, or make repairs, alterations or additions thereto and Tenant
shall not be entitled to any abatement or reduction of License Fee by reason of
any such entry.  [However, Landlord will use reasonable efforts to protect the
Tenant Equipment from damage or injury during any such entry.]

     18.  INDEMNIFICATION.  Intentionally deleted.
          ---------------

     19.  DAMAGE.  Landlord shall not be liable to Tenant for any loss or damage
          ------
to all or any part of the Tenant Equipment occasioned by theft, fire, act of
God, public enemy, injunction, riot, vandalism, malicious mischief, earthquake,
flood, strike, insurrection, war, court order, requisition, or order of
governmental body or authority, or by any other cause beyond the control of the
Landlord whatsoever.  Nor shall Landlord be liable for any damage or
inconvenience which may arise through the repair or alteration of any part of
the Building.

     20.  INSURANCE.  In addition to the insurance obligations of Tenant under
          ---------
the Lease, Tenant shall maintain a policy or policies of fire and extended
coverage insurance on the Tenant Equipment, in such amounts as Tenant may deem
appropriate;

                                     E-15
<PAGE>

     21.  TRANSFERS BY TENANT.  Except in connection with the transfer of the
          -------------------
Lease to an Affiliate as provided in Section 5.4 of the Lease, Tenant shall not
assign, convey, mortgage, pledge, hypothecate, encumber, or otherwise transfer
any license or grant any license, concession, or other right with respect to the
License without the prior written consent of Landlord, which consent may be
granted or withheld in Landlord's sole discretion; and the License shall, at
Landlord's sole option, terminate upon the occurrence of any attempted transfer
of the License or the Lease or upon a subletting of the Premises except in
connection with a transfer of the Lease to an Affiliate as provided for in the
Lease.

     22.  DEFAULT BY TENANT.  In addition to provisions of Article 8 of the
          -----------------
Lease, Tenant shall be deemed to be in default with respect to the License in
the event that (a) Tenant shall fail to pay the License Fees within ten (10)
days after Tenant's receipt of Landlord's written notice of such failure to pay;
provided Landlord shall be required to give such notice only twice in any twelve
(12) month period and thereafter Tenant shall be in default if any such payment
is not received when due and without notice, or (b) Tenant shall fail to
maintain the Tenant Equipment in good order and repair and in a safe condition
as provided in this Exhibit and shall fail to remedy that condition within [(i)]
twenty-four (24) hours after notice from Landlord [if such failure has an
adverse effect on Landlord or other tenants of the Building or creates a
possibility of immediate harm to person or property or (ii) thirty (30) days
after notice from Landlord in all other circumstances], or (c) Tenant shall fail
to maintain all necessary licenses and permits with respect to the operation of
the Tenant Equipment.  Upon a default by Tenant with respect to the License,
Landlord may, at Landlord's sole election, pursue the remedies granted to
Landlord for default under the Lease or, in the alternative, terminate any
License granted hereunder without terminating the Lease or terminating Tenant's
right to possession of the Leased Premises under the Lease.

     23.  SURVIVAL.  Certain provisions of this Exhibit relate to the rights and
          --------
obligations of Landlord and Tenant subsequent to the termination or expiration
of the Lease Term.  Such provisions include, without limitation, the restoration
obligations of Tenant under Paragraph 13 hereof and the indemnification
obligations of Tenant under Paragraph 19 hereof.  Such provisions shall survive
the expiration or other termination of the Lease Term and the License granted to
Tenant hereunder.

                                     E-16
<PAGE>

                                  SCHEDULE "1"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                   as Landlord and EQUINIX, INC., as Tenant

                                PRICING SCHEDULE
                                ----------------

Any conduits allowed by Landlord in addition to Paragraph 2.a. shall be at a
                 rate of $250.00 per diameter inch per month.

                                      S-1
<PAGE>

                                  SCHEDULE "2"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                    as Landlord and EQUINIX, INC., as Tenant

                                  SERVICE FEES
                                  ------------

                    The Service Fee is intentionally deleted

                                      S-2
<PAGE>

                                  SCHEDULE "3"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                    as Landlord and EQUINIX, INC., as Tenant

             LIST OF TENANTS TO WHOM LICENSEE MAY PROVIDE SERVICES
             =====================================================

                      AS MAY BE AMENDED FROM TIME TO TIME

MFS Intelenet of Texas (Worldcom)
Allegiance Telecom
IXC
Splitrock Communications
RSL
Communications
ENRON Communications
Time Warner Communications
MetroFiber Networks
Prism Communications
Logix
Focal Communications
Telegent
Wynstar
Verio, Inc.
Kintetsu Global
The Planet
Leasenet
Nextlink One
Nextlink Texas
American Telesource
Unicomp
Level 3

                                      S-3
<PAGE>

                                  SCHEDULE "4"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                    as Landlord and EQUINIX, INC., as Tenant

                  TELECOMMUNICATIONS EQUIPMENT SYSTEMS DIAGRAM
                  ============================================

This schematic describes the telecommunications equipment systems to be
installed for the limited purpose of the license described herein.

                                      S-4
<PAGE>

                                  SCHEDULE "5"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                    as Landlord and EQUINIX, INC., as Tenant

                         LOCATION OF COOLING EQUIPMENT
                         =============================

                                      S-5
<PAGE>

                                  SCHEDULE "6"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                    as Landlord and EQUINIX, INC., as Tenant

                            SITE TECHNICAL STANDARDS
                            ========================

1.   The fiber transmission cables and all copper telephone cables must be
     Teflon (or of City approved fire retardant material) jacketed type cable,
     and secured by either stainless steel clamps or approved equal when not run
     in EMT type conduit.  Excess transmission line must be removed.

2.   Each fiber or copper telephone line or conduit shall be identified with
     stainless steel tags that identifies the user/Licensee: (1) at the
     equipment cabinet; (2) at each side of horizontal/vertical penetration (3)
     as the line traverses the Building at a minimum of 72' intervals,
     coincident with column lines, and (4) at the termination point(s).

3.   The location and installation of all equipment and conduit will be
     designated by the site coordinator.  These locations will be shown on the
     License.  Changes must be approved in writing by the site coordinator.  Any
     conduit or cable failing to meet the above standards will be immediately
     removed from the Building at Licensee's expense.  In the event Licensee
     fails to promptly remove any such conduit or cable, Licensor may do so at
     Licensee's expense.

4.   On a 24-hour notice, the Site Equipment will be made available for
     inspection by the site coordinator to assure compliance with the above
     standards.

5.   The following information is essential for site coordination and must be
     provided.  Any and all changes must have prior approval and be reported to
     the site coordinator.

     a)  Manufacturer and model number of all end equipment.

     b)  Type and length of all cable and lines.

c)   The name, address and telephone number of the person or group directly
responsible for the day-to-day maintenance.

     d)  The name, address and telephone number of the person or group directly
         responsible for the License Agreement.

                                      S-6
<PAGE>

                                  SCHEDULE "7"
                                  ------------

To Exhibit D to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP,
                    as Landlord and EQUINIX, INC., as Tenant

                         LOCATION OF GENERATOR AND TANK
                         ==============================

                                       S-7
<PAGE>

                                  EXHIBIT "E"
                                  -----------
 To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord
                         and EQUINIX, INC., as Tenant

                                RENEWAL OPTIONS
                                ---------------

This Exhibit "E" describes the renewal option described below, which is being
granted upon the following terms and conditions:

1.   DEFINED TERMS.  For purposes of this Exhibit "E", all terms defined in this
     --------------
     Lease (including other exhibits to this Lease) will be used in this Exhibit
     without further definition.  In addition, when delineated with initial
     capital letters, the following terms shall have the following respective
     meanings:

     (a)  "Renewal Date" shall mean the first day next following the expiration
          date of the Lease Term.

     (b)  "Renewal Term" shall mean a period commencing on the Renewal Date and
          continuing for sixty (60) full calendar months.

     (c)  "Prevailing Market Rate" shall mean the rate of base rental rate being
          charged by Landlord to new tenants having a financial condition
          comparable to that of Tenant for comparable space within the Building
          for a comparable term as of the date of Tenant's exercise of the
          Option. For purposes of this Exhibit, the phrase "new tenants" shall
          mean (i) tenants who executed comparable leases within six (6) months
          prior to Tenant's exercise of the applicable Option or (ii) if no
          comparable lease exists within that six (6) month period, tenants who
          have executed comparable leases within twelve (12) months prior to
          Tenant's exercise of that Option.  Landlord shall notify Tenant of the
          then prevailing market rate ("Rate Notice") promptly after Tenant's
          exercise of the Option; and if such rate is not acceptable to Tenant,
          then Tenant has the right to rescind its exercise of the Option by
          providing a written revocation notice to Landlord within ten (10) days
          of Tenant's receipt of Landlord's Rate Notice.  In such case Tenant
          will have no further right to renew this Lease under Exhibit "E".

2.   GRANT OF OPTION.  Tenant shall have the following options ("Options") to
     ----------------
     renew this Lease:

     (a)  Tenant may, by notifying Landlord of its election in writing at least
          six (6) full calendar months prior to the end of the Lease Term, renew
          this Lease for the first (1/st/) Renewal Term. Such renewal shall be
          on all of the terms and conditions of this Lease which are not
          inconsistent with the terms of this Exhibit.

     (b)  The Base Rental payable beginning on the first (1/st/) Renewal Date
          and continuing for sixty (60) months thereafter shall be at the
          prevailing market rate.

                                      S-8
<PAGE>

     (c)  If Tenant exercises its option to renew this Lease for the first
          (1/st/) Renewal Term, then Tenant may, by notifying Landlord of its
          election in writing at least six (6) full calendar months prior to the
          end of the first (1/st/) Renewal Term, renew this Lease for the second
          (2/nd)/ Renewal Term. Such renewal shall be on all of the terms and
          conditions of this Lease which are not inconsistent with the terms of
          this Exhibit, except that no renewal option shall exist during the
          second (2/nd/) Renewal Term.

     (d)  The Base Rental payable beginning on the second (2/nd/) Renewal Date
          and continuing for sixty (60) months thereafter shall be at the
          prevailing market rate.

3.   GENERAL PROVISIONS.  Tenant's failure to notify Landlord of Tenant's
     ------------------
     election to exercise the Option in the manner and within the specified time
     limit, shall constitute an irrevocable waiver of such Option.  Tenant's
     failure to provide Landlord with a revocation notice in the manner and
     within the specified time limit shall be an irrevocable waiver of Tenant's
     revocation option.  Notwithstanding the foregoing, the Option shall not be
     applicable at any time when there is an uncured event of default under the
     Lease.  In addition, the Option shall automatically terminate upon the
     termination of the Lease Term, whether by Landlord upon the occurrence of
     an event of default or otherwise or, at the option of Landlord, in its sole
     discretion, upon the assignment, subletting, or other transfer by Tenant,
     whether or not with the approval of Landlord, to any person or entity other
     than to an Affiliate allowed by the provisions of this Lease.

 -----------------------------------------------------------------------------
                                     INITIALS
 Landlord___________________                          Tenant _________________
 -----------------------------------------------------------------------------
                                      S-9
<PAGE>

                                  EXHIBIT "F"
                                  -----------

To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord
                          and EQUINIX, INC., as Tenant
_______________________________________________________________________________
                         SUBORDINATION, ATTORNMENT AND
                           NON-DISTURBANCE AGREEMENT

          This SUBORDINATION, ATTORNMENT AND NON-DISTURBANCE AGREEMENT (this

"Agreement"), is made as of the _______ day of ______, 1999, between GERMAN
----------
AMERICAN CAPITAL CORPORATION and its successors and assigns ("Beneficiary"),
                                                              -----------
[LANDLORD] ("Landlord") and [TENANT] ("Tenant").
             --------                  ------

          WHEREAS, Beneficiary has agreed to make a loan to Landlord to be
secured by a Deed of Trust, Security Agreement, Financing Statement, Fixture
Filing and Assignment of Leases, Rents and Security Deposits (together with any
UCC-1 Financing Statements in connection therewith, the "Mortgage"), as well as
                                                         --------
by a separate Assignment of Leases, Rents and Security Deposits (the

"Assignment"; the Assignment and the Mortgage, as the same may hereafter be
 ----------
amended, modified, extended, consolidated, severed, spread, increased, replaced
or supplemented, are collectively referred to as the "Security Documents")
                                                      ------------------
covering Landlord's interest in certain real and personal property located in
Dallas, Texas and more particularly described in Exhibit A hereto (the
"Property"); and
 --------

          WHEREAS, Tenant has entered into a certain lease, as the same may have
been amended, modified or supplemented (the "Lease") dated ________________,
                                             -----
19__, with Landlord (or its predecessor), covering a certain portion of the
Property (the "Premises"); and
               --------

          WHEREAS, Beneficiary, Landlord and Tenant desire to confirm their
understanding, with respect to the Lease, the Mortgage and the Assignment;

          NOW, THEREFORE, in consideration of the promises set forth herein, and
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the parties hereby agree as follows:

          1.   Subordination.  Subject to the provisions hereof, Tenant agrees
               -------------
that the Lease, as it may hereafter be amended from time to time, shall in all
respects be, and is hereby expressly made, subject and subordinate at all times
to the lien of the Security Documents and to all of the terms, conditions and
provisions thereof and to all advances and/or payments made or to be made
thereunder, as the same may hereafter be amended from time to time.  Nothing
contained in this Agreement shall in any way impair or affect the lien created
by the Security Documents.

          2.   Attornment.
               ----------

               (a)  In the event that Beneficiary acquires or succeeds to the
interests of Landlord under the Lease by reason of a foreclosure, deed-in-lieu
of foreclosure or otherwise (collectively, a "Foreclosure"), Tenant shall be
                                              -----------
bound to Beneficiary under all of the terms, covenants and conditions of the
Lease, except as provided in this Agreement, for the balance of

                                     S-10
<PAGE>

the term thereof remaining, with the same force and effect as if Beneficiary
were Landlord. Tenant hereby agrees in such event to (i) attorn to Beneficiary
as its landlord on such terms, (ii) affirm its obligations under the Lease, and
(iii) make payments of all sums thereafter becoming due under the Lease to
Beneficiary. Said attornment, affirmation and agreement is to be effective and
self-operative without the execution of any further instruments upon Beneficiary
succeeding to the interests of Landlord under the Lease.

               (b)  Tenant agrees to execute and deliver at any time and from
time to time, upon the request of Landlord or Beneficiary, any instrument or
certificate deemed to be necessary or appropriate to evidence such attornment.

               (c)  If any act or omission of Landlord would give Tenant the
right, immediately or after the lapse of a period of time, to cancel or
terminate the Lease or abate the rent payable thereunder or to claim a partial
or total eviction, Tenant shall not exercise such right until (i) it has given
written notice of such act or omission to Landlord and Beneficiary, (ii)
Landlord fails to remedy such act or omission within the applicable time period
stated in the Lease for effecting such remedy and (iii) a reasonable period for
remedying such act or omission shall have elapsed following the failure of
Landlord to effect such remedy and following the time when Beneficiary shall
have become entitled under the Mortgage to remedy the same (which reasonable
period shall in no event be less than the period to which Landlord is entitled
under the Lease or otherwise, after similar notice, to effect such remedy, plus
two additional weeks). In the case of an act or omission which Beneficiary
undertakes to remedy but which cannot practicably be remedied by Beneficiary
without taking possession of the Premises [and provided that Beneficiary
notifies Tenant in writing that Beneficiary will in fact cure that default as
soon as reasonably practicable after Beneficiary has taken possession, then] (i)
such reasonable period shall not commence until Beneficiary has possession of
the Premises and (ii) Beneficiary shall proceed with reasonable diligence to
obtain possession of the Premises, and upon obtaining such possession shall with
reasonable diligence remedy such act or omission.

               (d)  From and after such attornment, Beneficiary shall be bound
to Tenant under all the terms, covenants and conditions of the Lease; provided,
however, Beneficiary shall not be:

                    (1)  obligated to cure any defaults under the Lease of any
prior landlord (including Landlord) which occurred prior to the date Beneficiary
obtained title to or possession of the Property;

                    (2)  liable for any act or omission of any prior landlord
(including Landlord) which occurred prior to the date Beneficiary obtained title
or possession of the Property;

                    (3)  obligated to fund any security deposit unless actually
received by Beneficiary;

                    (4)  bound by any amendment, modification or termination of
the Lease unless such amendment, modification or termination was consented to in
writing by Beneficiary;

                                     S-11
<PAGE>

                    (5)  subject to any offsets or defenses which Tenant might
have against any prior landlord (including Landlord); or

                    (6)  bound by any base rental or additional rental or
advance payment of rent which Tenant paid for more than the current month to any
prior landlord (including Landlord).

               (e)  Anything herein or in the Lease to the contrary
notwithstanding, in the event that Beneficiary shall acquire title to the
Premises by reason of a Foreclosure, Beneficiary shall have no obligation, nor
incur any liability, beyond Beneficiary's then interest, if any, in the Property
(including any title and casualty insurance proceeds and condemnation awards
actually paid to Beneficiary), and Tenant shall look exclusively to such
interest of Beneficiary in the Property for the payment and discharge of any
obligations which may be imposed upon Beneficiary hereunder or under the Lease.

          3.   Non-Disturbance.  Provided Tenant is not in default under the
               ---------------
terms of the Lease and complies with this Agreement, Beneficiary agrees that in
the event Beneficiary acquires title to the Property by reason of a Foreclosure,
Tenant's possession and occupancy of the Premises and Tenant's rights and
privileges under the Lease during the term thereof (including any renewal term)
shall not be disturbed, subject to limitations or conditions set forth in this
Agreement and Beneficiary shall recognize the Lease and Tenant's rights
hereunder.  Subject to the limitations and conditions contained herein,
Beneficiary upon Foreclosure shall be deemed to be Landlord and shall assume the
obligations of Landlord under the Lease thereafter arising or accruing.

          4.   Notices.
               -------

          (a)  All notices, demands and requests (collectively the "Notices")
required or permitted to be given under this Agreement must be in writing and
shall be deemed to have been given if personally delivered or delivered by
reliable overnight courier or mailed by certified mail, return receipt
requested, postage prepaid and shall be deemed delivered as of the date of such
Notice if (i) delivered to the party intended; (ii) delivered to the then
current address of the party intended, or (iii) rejected at the then current
address of the party intended, provided such Notice was sent prepaid. The
addresses of the parties are:

     If to Beneficiary:           German American Capital Corporation
                                  31 West 52/nd/ Street
                                  New York, New York  10019[ ]
                                  Attention:  General Counsel

     If to Tenant:                _____________________________________________
                                  _____________________________________________
                                  _____________________________________________

                                     S-12
<PAGE>

     If to Landlord:              _____________________________________________
                                  _____________________________________________
                                  _____________________________________________

                    (b)  Upon at least ten (10) days prior written Notice, each
party shall have the right to change its address to any other address within the
United States of America.

               5.   Miscellaneous. This Agreement (i) contains the entire
                    -------------
agreement with respect to the subject matter hereof; (ii) may not be modified or
terminated, nor may any provision hereof be waived, orally or in any manner
other than by an agreement in writing signed by the parties hereto or their
respective successors, administrators and assigns; and (iii) shall inure to the
benefit of, and be binding upon, the parties hereto, and their successors and
assigns (including, without limitation, (a) Tenant's permitted assignees and (b)
any purchaser of the Property pursuant to a Foreclosure).

               6.   Applicable Law. This Agreement shall be governed by and
                    --------------
construed in accordance with the laws of the state in which the Property is
located.

               IN WITNESS WHEREOF, Beneficiary, Landlord and Tenant have
executed this Agreement effective as of the day and year first above written.

                                 GERMAN AMERICAN CAPITAL CORPORATION

                                 By:___________________________________________
                                 Its:

                                 [TENANT]

                                 By:___________________________________________
                                 Its:

                                 [LANDLORD]

                                 By:___________________________________________
                                 Its:

                                     S-13
<PAGE>

                                  EXHIBIT "G"
                                  -----------

To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord
                          and EQUINIX, INC., as Tenant

                                    PARKING
                                    -------

This Exhibit "F" describes and specifies Tenant's non-exclusive option, but not
the obligation to use non-reserved parking spaces ("Garage Spaces") located
inside the Building's exterior card access parking garage ("Parking Garage"),
and reserved parking spaces ("Lower Level Spaces") on the lower level of the
Building's interior card access parking garage ("Lower Level Garage"). For
convenience, the Garage Spaces and the Lower Level Spaces will sometimes be
collectively referred to as the "Spaces" in this Exhibit.  Landlord reserves the
right at Landlord's sole discretion to relocate any of the Spaces.
Additionally, spaces in the surface parking lots associated with the Building
and located on the Property ("Surface Parking") are provided for the non-
exclusive and common use of Landlord, all tenants of the Building, and their
respective guests and invitees.  Utilization of the Surface Parking is subject
to availability (and Landlord shall have no obligation to provide available
Surface Parking) and to such rules and regulations as may be promulgated by
Landlord from time to time.  Use of the Parking Garage, Lower Level Garage and
the Surface Parking is subject to the terms and conditions set forth below.

1.   DEFINITIONS.  Terms which are defined in the Lease will be used without
     -----------
     further definition in this Exhibit.

2.   GRANT AND RENTAL FEE.  Provided no event of default has occurred and is
     --------------------
     continuing under the Lease, Tenant shall be permitted non-exclusive use of
     Spaces in the Parking Garage during the Lease Term for the parking of
     fifty-three (53) vehicles at such monthly rates and subject to such terms,
     conditions, and regulations as are, from time to time, promulgated by
     Landlord and charged or applicable to patrons of said parking Garage for
     spaces similarly situated within said Parking Garage. The parking rate for
     each of the Spaces as of the date hereof is $45.00. Provided no event of
     default has occurred and is continuing under the Lease, Tenant shall be
     permitted exclusive use of eighteen (18) reserved Lower Level Spaces in the
     Lower Level Garage upon availability during the Lease Term at such monthly
     rates and subject to such terms, conditions, and regulations as are, from
     time to time, promulgated by Landlord and charged or applicable to patrons
     of said Lower Level Garage. The parking rate for each of the Lower Level
     Spaces as of the date hereof is $60.00 for spaces designated on the
     attached Schedule 1 "Lower Level Garage Pricing Schedule" as "circle"
     parking and $90.00 for spaces designated as "diamond" parking. Tenant shall
     also have the right to use the Surface Parking, free of charge, during the
     Lease Term.

3.   RISK.  All motor vehicles (including all contents thereof) shall be parked
     ----
     in the Garage Spaces, Lower Level Spaces or in the Surface Parking, as
     applicable, at the sole risk of Tenant, its employees, agents, invitees and
     licensees, it being expressly agreed and understood that Landlord has no
     duty to insure any of said motor vehicles (including the contents thereof),
     and that Landlord is not responsible for the protection and security of
     such vehicles. Landlord shall have no liability whatsoever for any property
     damage

                                     S-14
<PAGE>

     and/or personal injury which might occur as a result of or in connection
     with the parking of said motor vehicles in any of the Garage Spaces, Lower
     Level Spaces or in the Surface Parking, as applicable, and Tenant hereby
     agrees to indemnify and hold Landlord harmless from and against any and all
     costs, claims, expenses, and/or causes of action which Landlord may incur
     in connection with or arising out of Tenant's use of the Garage Spaces,
     Lower Level Spaces or the Surface Parking pursuant to this Agreement.

4.   RULES AND REGULATIONS.  In its use of the Garage Spaces, Lower Level Spaces
     ---------------------
     and the Surface Parking, Tenant shall follow all of the Rules and
     Regulations of the Building (attached to the Lease as Exhibit "B")
     applicable thereto, as the same may be amended from time to time. Upon the
     occurrence of any breach of such rules or default by Tenant under the
     Lease, Landlord shall be entitled to terminate this Exhibit, in which event
     Tenant's right to utilize the Garage Spaces, Lower Level Spaces and/or the
     Surface Parking shall thereupon automatically cease.

5.   SECURITY.  Landlord shall be entitled to utilize whatever access device
     --------
     Landlord deems necessary (including but not limited to the issuance of
     parking stickers or access cards), to insure that only tenants authorized
     to use spaces in the Parking Garage and Lower Level Garage are using such
     spaces. In the event Tenant, its agents or employees wrongfully park in any
     of the Parking Garage's or Lower Level Parking Garage's spaces, Landlord
     shall be entitled and is hereby authorized to have any such vehicle towed
     away, at Tenant's sole risk and expense, and Landlord is further authorized
     to impose upon Tenant a penalty of $25.00 for each such occurrence. Tenant
     hereby agrees to pay all amounts falling due hereunder upon demand
     therefor, and the failure to pay any such amount shall additionally be
     deemed an event of default under the Lease, entitling Landlord to all of
     its rights and remedies thereunder.

6.   ADDITIONAL SPACES.  In the event that Tenant expands the Leased Premises,
     -----------------
     Tenant shall be entitled to additional Garage Spaces within the Parking
     Garage based upon a ratio of one (1) additional Space per additional 1,000
     Usable Square Feet incorporated into the Leased Premises and additional
     Lower Level Spaces within the Lower Level Garage based upon a ratio of one
     (1) reserved parking space per 3,000 Rentable Square Feet incorporated into
     the Lease Premises upon availability. Such additional Garage Spaces and
     Lower Level Spaces shall be subject to such monthly rates, terms,
     conditions, and regulations as are, from time to time, promulgated by
     Landlord and charged or applicable to patrons of said Parking Garage or
     Lower Level Garage for spaces similarly situated within said Parking Garage
     or Lower Level Garage.

Schedule 1- Lower Level Garage Price Schedule

 ------------------------------------------------------------------------------
                                   INITIALS
   Landlord___________________                   Tenant________________________
 ------------------------------------------------------------------------------

                                     S-15
<PAGE>

                                 SCHEDULE "1"
                                 ------------

To Exhibit E to Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP.,
                   as Landlord and [TENANT NAME], as Tenant

________________________________________________________________________________

                       Lower Level Garage Price Schedule
                       (For illustrative purposes only)

                                     S-16
<PAGE>

                                  EXHIBIT "H"
                                  -----------

To Lease Agreement By and Between NEXCOMM ASSET ACQUISITION I, LP, as Landlord
                         and EQUINIX, INC., as Tenant

                                  WORK LETTER
                                  -----------

This Work Letter ("Work Letter") describes and specifies the right and
obligations of Landlord and Tenant with respect to certain allowances granted to
Tenant hereunder and rights and responsibilities of Landlord and Tenant with
respect to the design, construction and payment for the completion of Tenant's
installation of the Tenant Equipment defined in Exhibit D (the "Improvements")
within the Leased Premises, in the Building or on the Property.

          1.   DEFINITIONS.  Terms which are defined in the Lease shall have the
               ------------
same meaning in this Work Letter.  Additionally, as used in this Work Letter,
the following terms (when delineated with initial capital letters) shall have
the respective meaning indicated for each as follows:

               (a)  "Allowance" is intentionally omitted.
                     ---------

               (b)  "Basic Construction of the Building" shall mean the
                     ----------------------------------
structure of the Building as built on the date of this Work Letter.

               (c)  "Landlord's Architect" shall mean the architect designated
                     --------------------
by Landlord as its architect, from time to time, to perform the functions of
Landlord's Architect hereunder.

               (d)  "Plans and Specifications" shall mean collectively, the
                     ------------------------
plans, specifications and other information prepared or to be prepared by
Tenant's Architect and, where necessary, by Landlord's electrical, mechanical
and structural engineers, all at Tenant's expense, which shall detail the Work
required by Tenant in the Leased Premises and which shall be approved in writing
by both Tenant and Landlord prior to the commencement of such Work.

               (e)  "Tenant's Architect" shall mean an architect, selected by
                     ------------------
Tenant, and approved by Landlord in an exercise of reasonable discretion who is
an architect licensed to practice in the State of Texas.

               (f)  "Work" shall mean all materials and labor to be added to the
                     ----
Basic Construction of the Building in order to complete the installation of the
Improvements within the Leased Premises, in the Building or on the Property for
Tenant in accordance with the Plans and Specifications, including, without
limitation any modifications to the Building, any electrical or plumbing work
required to meet Tenant's electrical and plumbing requirements, and any special
air conditioning work required to be performed in the Leased Premises, in the
Building or on the Property.

               (g)  "Cost of the Work" shall mean the cost of all materials and
                     ----------------
labor to be added to the Basic Construction of the Building in order to complete
the installation of the

                                     S-17
<PAGE>

Improvements within the Leased Premises, in the Building or on the Property in
accordance with the Plans and Specifications.

               (h)  "Tenant's Costs" shall mean that portion of the Cost of the
                     --------------
Work in excess of Allowance.

               (i)  "Change Costs" shall mean all costs or expenses attributable
                     ------------
to any change in the Plans and Specifications which, when added to other costs
and expenses incurred in completing the Work, exceed Allowance, including,
without limitation, (i) any cost caused by direction of Tenant to omit any item
of Work contained in the Plans and Specifications, (ii) any additional
architectural or engineering services, (iii) any changes to materials in the
process of fabrication, (iv) the cancellation or modification of supply or
fabricating contracts, (v) the removal or alteration of any Work or any plans
completed or in process, or (vi) delays affecting the schedule of the Work.

               (j)  "Working Days" shall mean all days of the week other than
                     ------------
Saturday, Sunday, and legal holidays.

               (k)  "Contractor" shall mean the contractor or contractors
                     ----------
engaged by Tenant to perform the Work in accordance with the provisions of
Section 4.2(b) of the Lease.

          2.   PROCEDURE AND SCHEDULES FOR THE COMPLETION OF PLANS AND
               -------------------------------------------------------
SPECIFICATIONS.  The Plans and Specifications shall be completed in accordance
---------------
with the following procedure and time schedules:v

          (a)  Design Drawings.  Within ninety (90) Working Days from execution
               ---------------
of the Lease, Tenant shall submit to Landlord four (4) sets of prints of design
drawings, specifying the intended design, character and finishing of the
Improvements within the Leased Premises, in the Building or on the Property.
Such package shall include separate drawings for signs in accordance with
Landlord's sign criteria. The design drawings shall set forth the requirements
of Tenant with respect to the installation of the Improvements within the Leased
Premises, in the Building or on the Property, and such drawings shall include,
without limiting their scope, a Tenant approved space plan, architectural design
of the space, including office front, plans, elevations, sections, and
renderings indicating materials, color selections and finishes.

                    (i)  After receipt of design drawings, Landlord shall return
to Tenant one set of Prints of design drawings with Landlord's suggested
modifications and/or approval. If, upon receipt of approved design drawings
bearing Landlord's comments, Tenant wishes to take exception thereto, Tenant may
do so in writing, by certified mail addressed to Landlord, within five (5)
Working Days from the date of receipt of Landlord's comments on the design
drawings. Unless such action is taken, Tenant will be deemed to have accepted
and approved all of Landlord's comments on the design drawings.

                    (ii) If design drawings are returned to Tenant with
comments, but not bearing approval of Landlord, the design drawings shall be
immediately revised by Tenant and resubmitted to Landlord for approval within
ten (10) Working Days of their receipt by Tenant.

                                     S-18
<PAGE>

          (b)  Completion of Plans and Specifications.  All Plans and
               --------------------------------------
Specifications shall be prepared in strict compliance with applicable Building
standards and requirements, this Work Letter and otherwise, and shall also
adhere to the design drawings approved by Landlord. In order to assure the
compatibility of Tenant's electrical and mechanical systems and the
compatibility of Tenant's structural requirements with the existing Building and
in order to expedite the preparation of Tenant's electrical, mechanical and
structural drawings, Tenant or Tenant's Architect shall deliver to Landlord's
Architect, not later than thirty (30) Working Days from the date of Landlord's
approval of design drawings, a detailed plan setting forth any and all
electrical, mechanical and structural requirements, and Landlord's Architect
shall retain, at Tenant's expense, Landlord's electrical, mechanical and
structural engineers to prepare all necessary electrical, mechanical and
structural construction drawings which shall be included as a part of the Plans
and Specifications. All construction documents and calculations prepared by
Tenant's Architect shall be submitted by Tenant, in the form of four (4) sets of
blueline prints, to Landlord for approval within ten (10) Working Days after the
date of receipt by Tenant of Landlord's approval of design drawings. If the
Plans and Specifications are returned to Tenant with comments, but not bearing
approval of Landlord, the Plans and Specifications shall be immediately revised
by Tenant and resubmitted to Landlord for approval within fifteen (15) Working
Days of their receipt by Tenant.

                    (i)  The fees for Tenant's Architect and any consultants or
engineers retained by or on behalf of Tenant or Tenant's Architect (including,
but not limited to, the electrical, mechanical and structural engineers required
to be retained under this paragraph) shall be paid by Tenant. Tenant shall also
pay for any preliminary drawings by Landlord's Architect for review of the
design drawings, the Plans and Specifications, and any revisions to such
documents, and the fees and expenses of Landlord's Architect for inspection of
the Work, as required by Landlord. Tenant may use funds from the Allowance to
make such payments.

                    (ii) Tenant shall have the sole responsibility for
compliance of the Plans and Specifications with all applicable statutes, codes,
ordinances and other regulations, and the approval of the Plans and
Specifications or calculations included therein by Landlord shall not constitute
an indication, representation or certification by Landlord that such Plans and
Specifications or calculations are in compliance with said statutes, codes,
ordinances and other regulations. In instances where several sets of
requirements must be met, the requirements of Landlord's insurance underwriter
or the strictest applicable requirements shall apply where not prohibited by
applicable codes.

          3.  TERMINATION RIGHT.  If for any reason (other than default by
              -----------------
Tenant) Landlord and Tenant have not agreed in writing upon final Plans and
Specifications on or before the date which is ninety (90) Working Days from the
date hereof, then Landlord or Tenant shall have the right to terminate the Lease
by providing the other party with written notice of the electing parties'
decision to terminate this Lease within thirty (30) days from the expiration of
such ninety (90) day period.  The failure of either party to exercise such
termination right in the manner and within the time period specified above shall
be deemed to be an irrevocable waiver of such right.

          4.  PAYMENT.  In the event Landlord acts as the general contractor for
              -------
the Improvements in the Leased Premises, in the Building or on the Property, the
Allowance will be

                                     S-19
<PAGE>

applied to offset the amounts due Landlord as reflected in the monthly invoices
therefor submitted by Landlord to Tenant. In the event Landlord does not act as
the general contractor for the Improvements in the Leased Premises, in the
Building or on the Property, Landlord shall pay the Allowance to Tenant within
forty-five (45) days of Landlord's receipt of general contractor's waiver of
lien submitted by Tenant to Landlord.

          5.  PERFORMANCE OF WORK AND DELAYS.  Tenant shall cause the Contractor
              ------------------------------
to perform the Work in strict accordance with the Plans and Specifications.  If
a delay shall occur in the completion of the Work by Tenant as the probable
result of (i) any failure to furnish when due Tenant's design drawings, Tenant's
electrical, mechanical and/or structural requirements, Tenant's Plans and
Specifications or any revision to any such documents, (ii) any change by Tenant
in any of the Plans and Specifications, (iii) any state of facts which gives
rise to a change referred to in the definition of Change Costs or any changes
resulting in a Change Cost, (iv) any other act or omission of Tenant, its agents
or employees, including any violation of the provisions of the Lease or any
delay in giving authorizations or approvals pursuant to this Work Letter, or (v)
any other cause except (a) as specified in Section 8.1 of the Lease or (b)
arising from a default by Landlord, then any such delay shall not justify any
                                                              ---
extension of the Commencement Date of the Lease.

          6.  CHANGE ORDERS.  All changes and modifications in the Work from
              -------------
that contemplated in the Plans and Specifications, whether or not such change or
modification gives rise to a Change Cost, must be evidenced by a written Change
Order executed by both Landlord and Tenant.  In that regard, Tenant shall submit
to Landlord such information as Landlord shall require with respect to any
Change Order requested by Tenant.  After receipt of requested Change Order,
together with such information as Landlord shall require with respect thereto,
Landlord shall return to Tenant either the executed Change Order, which will
evidence Landlord's approval thereof, or the Plans and Specifications with
respect thereto with Landlord's suggested modification.

          7.  WHOLE AGREEMENT; NO ORAL MODIFICATION.  This Work Letter embodies
              -------------------------------------
all representations, warranties and agreements of Landlord and Tenant with
respect to the matter described herein, and this Work Letter may not be altered
or modified except by an agreement in writing signed by the parties.

          8.  PARAGRAPH HEADINGS.  The paragraph headings contained in this Work
              ------------------
Letter are for convenient reference only and shall not in any way affect the
meaning or interpretation of such paragraphs.

          9.  NOTICES.  All notices required or contemplated hereunder shall be
              -------
given to the parties in the manner specified for giving notices under the Lease.

          10. BINDING EFFECT.  This Work Letter shall be construed under the
              --------------
laws of the State of Texas and shall be binding upon and shall inure to the
benefit of the parties hereto and their respective permitted successors and
assigns.

          11. CONFLICT.  In the event of conflict between this Work Letter and
              --------
any other exhibits or addenda to this Lease, this Work Letter shall prevail.

                                     S-20
<PAGE>

--------------------------------------------------------------------------------
                                   INITIALS
   Landlord __________                                  Tenant _______________
--------------------------------------------------------------------------------

                                     S-21
<PAGE>

                      THIS PAGE INTENTIONALLY LEFT BLANK

                                     S-22<PAGE>

                                                                   EXHIBIT 10.15

                          MEMORANDUM OF UNDERSTANDING

                                    BETWEEN

                     NETSTAR INTERNATIONAL HOLDING LIMITED
                                      AND
                           oCEN COMMUNICATIONS, INC.

                                MARCH 15, 2000

This document summarizes the proposed terms of cooperation for IP communications
deployment between oCen Communications, Inc. of the United States (oCen) and
NetStar International Holding Limited (NetStar).

Parties                            oCen Communications, Inc., 4900 Rivergrade
                                   Road, C110, Irwindale, CA 91706, a US-based
                                   IP communications services provider.

                                   NetStar International Holding Limited, 22/F,
                                   Pearl Oriental Center, 200 Gloucester Road,
                                   Wanchai, Hong Kong, a Hong Kong based
                                   communications and network integration
                                   specialist.

Preamble                           oCen is a leading IP-based communications
                                   services provider focused on the North
                                   American and Asian markets. oCen has built
                                   one of the largest managed IP networks in US-
                                   Asia dedicated for Internet telephony and
                                   other real time and enhanced IP
                                   communications services. With this state-of-
                                   art IP network, oCen develops and markets
                                   high quality, innovative communications
                                   services to its customers -consumers,
                                   carriers and corporations - in the US and
                                   Asia.

                                   NetStar is a leader in the Asia Pacific
                                   region specializing in integrating and
                                   servicing enterprise networks and network
                                   enabled business solutions. NetStar is
                                   committed to building working partnerships
                                   with its customers and strategic suppliers.
                                   With its operational headquarters in Hong
                                   Kong. NetStar has offices in Australia, China
                                   and Taiwan, and has a close working
                                   relationship with leading suppliers such as
                                   Nortel, Cisco and 3Com providing pre and
                                   after-sales network integration solutions.

                                   With oCen as an innovator in the Voice over
                                   IP (VoIP) and IP-based communications space
                                   and NetStar as a leader in enterprise
                                   networking solutions, together both Parties
                                   can deliver better solutions to their
                                   respective customers. Based on their
                                   compatible interest in developing a long-term
                                   cooperation in IP telephony and other IP-
                                   based communications services both Parties
                                   have discussed their planned cooperation and
                                   entered into this Memorandum of Understanding
                                   (MoU).

Terms and Conditions

Overview of Responsibilities       1.   oCen and NetStar agree to partner with
                                        each other to launch IP-based
                                        communications services for corporate
                                        clients in the international market,
                                        beginning with a beta launch in Taiwan
                                        by March 2000 and subsequent rollout
                                        across Greater China by June 2000.

                                   2.   oCen and NetStar will provide joint
                                        sales leads for Voice over IP (VoIP),
                                        Fax over IP (FoIP), IP-based Virtual
                                        Private Networking (VPN) and other
                                        enhanced communications services
                                        utilizing oCen managed IP network and
                                        branded CommPortal services.

[*] = CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY
WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO
THE OMITTED PORTIONS.
<PAGE>

                                   3.   oCen will enter into service
                                        negotiations and contractual agreements
                                        with all corporate clientele for IP
                                        communications traffic and usage.
                                        Account management, monitoring, services
                                        dispatch and billing will also be
                                        controlled and administered by oCen.

                                   4.   NetStar will be responsible for
                                        technical site surveys, installation of
                                        VoIP gateways and relevant equipment at
                                        customer premises, testing and circuits
                                        and equipment, ongoing technical
                                        maintenance and service support. This
                                        will require NetStar to develop a
                                        working expertise regarding all
                                        necessary equipment, including but not
                                        restricted to Clarent gateways, Cisco
                                        routers, PBXs and ADSL technology.

                                   5.   oCen will be solely responsible for all
                                        network operations and maintenance.

            Trial Launch           1.   NetStar Taiwan agrees to participate in
                                        oCen's trial launch of basic IP
                                        telephony services commencing in Taiwan
                                        on March 7, 2000, post date of local
                                        loop provisioning. This requires the
                                        deployment of an 8-port analog Clarent
                                        enterprise gateway at the NetStar Taiwan
                                        site and a local loop connection between
                                        NetStar Taiwan and oCen Taiwan's data
                                        center, applied for by oCen on NetStar's
                                        behalf. The purpose of the trial will be
                                        to test the VoIP/FoIP technologies and
                                        IP network quality, as well as to
                                        provide hands-on experience in
                                        installing, configuring and maintaining
                                        all gateway and router equipment for
                                        both oCen and NetStar deployment terms.
                                        NetStar will provide the router and pay
                                        for the NetStar Taiwan image minutes
                                        using the current oCen route table.

                                   2.   NetStar agrees to refer 1 additional
                                        corporate trial customers with the
                                        following criteria: high volume IDD call
                                        pattern, existing PBX and router in
                                        place, situated within Greater Taipei
                                        locale. oCen will provide the local loop
                                        and VoIP gateway. NetStar will provide
                                        the router to the customer.

                                   3.   Upon a successful trial of basic IP
                                        telephony services within the enterprise
                                        mode, both Parties will initiate a
                                        CommPortal and IP VPN trial launch
                                        across Greater China together.

            Financial Terms        1.   XXXXXXX

                                   2.   XXXXXXXXXXXXXXXXXXXXXXX

                                   3.   XXXXXXXXXXXXXXXXXXXXXXX

                                   4.   XXXXXXXXXXXXXXXXXXXXXXX

                                   5.   XXXXXXXXXXXXXXXXXXXXXXX

Confidentiality                    Both Parties, including but not limited to
                                   employees, subsidiaries, and legal advisors,
                                   agree to treat all information exchanged with
                                   strict confidentiality, in the same manner as
                                   if the information was their own, and not to
                                   disclose to any third parties any information
                                   related to the terms contained herein unless
                                   required by applicable law and jointly
                                   approved in writing by both Parties.

Subsequent Agreement               Following the execution by both parties and
                                   approval by oCen's Board of Directors of this
                                   Memorandum of Understanding, the Parties
                                   shall negotiate a

[*] = CERTAIN INFORMATION ON THIS PAGE HAS BEEN OMITTED AND FILED SEPARATELY
WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO
THE OMITTED PORTIONS.
<PAGE>

                              detailed Enterprise Services Agreement the terms
                              and conditions which shall supersede this
                              Memorandum of Understanding to the extent there
                              are inconsistent provisions.

Binding Effect                Subject to the approval of this Memorandum of
                              Understanding by oCen's Board of Directors, the
                              terms and conditions of this Memorandum of
                              Understanding shall be legally binding on both
                              parties.

Signed and Agreed:
                              _________________________________________________
                              oCen Communications, Inc. (oCen)

                              Name/Title: Alex Liu, Managing Director of Asia

                              Date:

                              _________________________________________________
                              NetStar International Holding Limited (NetStar)

                              Name/Title: KH Wun, CEO

                              Date:

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