Document:

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                                                                    EXHIBIT 10.3

                              AVICI SYSTEMS INC.

                       2000 EMPLOYEE STOCK PURCHASE PLAN

ARTICLE 1 - PURPOSE.
-------------------

   This 2000 Employee Stock Purchase Plan (the "Plan") is intended to encourage
stock ownership by all eligible employees of Avici Systems Inc. (the "Company"),
a Delaware corporation, and its participating subsidiaries (as defined in
Article 17) so that they may share in the growth of the Company by acquiring or
increasing their proprietary interest in the Company.  The Plan is designed to
encourage eligible employees to remain in the employment of the Company and its
participating subsidiaries.  The Plan is intended to constitute an "employee
stock purchase plan" within the meaning of Section 423(b) of the Internal
Revenue Code of 1986, as amended (the "Code").

ARTICLE 2 - ADMINISTRATION OF THE PLAN.
--------------------------------------

   The Plan may be administered by a committee appointed by the Board of
Directors of the Company (the "Committee").  The Committee shall consist of not
less than two members of the Company's Board of Directors.  The Board of
Directors may from time to time remove members from, or add members to, the
Committee.  Vacancies on the Committee, howsoever caused, shall be filled by the
Board of Directors.  The Committee may select one of its members as Chairman,
and shall hold meetings at such times and places as it may determine.  Acts by a
majority of the Committee, or acts reduced to or approved in writing by a
majority of the members of the Committee, shall be the valid acts of the
Committee.

   The interpretation and construction by the Committee of any provisions of the
Plan or of any option granted under it shall be final, unless otherwise
determined by the Board of Directors.  The Committee may from time to time adopt
such rules and regulations for carrying out the Plan as it may deem best,
provided that any such rules and regulations shall be applied on a uniform basis
to all employees under the Plan.  No member of the Board of Directors or the
Committee shall be liable for any action or determination made in good faith
with respect to the Plan or any option granted under it.

   In the event the Board of Directors fails to appoint or refrains from
appointing a Committee, the Board of Directors shall have all power and
authority to administer the Plan.  In such event, the word "Committee" wherever
used herein shall be deemed to mean the Board of Directors.

ARTICLE 3 - ELIGIBLE EMPLOYEES.
------------------------------

   All employees of the Company or any of its participating subsidiaries whose
customary employment is more than 20 hours per week and for more than five
months in any calendar year and who have completed at least 7 days of employment
shall be eligible to receive options under the Plan to purchase common stock,
par value $0.0001 per share, of the Company (the "Common Stock"), and all
eligible employees shall have the same rights and privileges hereunder.  Persons
who are eligible employees on the first business day of the First Offering
Period (as defined in Article 5) shall receive their options as of such day.
Persons who become eligible employees after any date on which options are
granted under the Plan shall be granted options on the first day of the next
succeeding Offering Period (as defined in Article 5) on which options are
granted to eligible employees under the Plan.
<PAGE>

                                      -2-

Persons who remain eligible employees immediately following completion of any
Offering Period in which they participate shall be granted additional options on
the first day of the next succeeding Offering Period on which options are
granted to eligible employees under the Plan; it being the intention that
employees may participate in succeeding (but not overlapping) Offering Periods.
In no event, however, may an employee be granted an option if such employee,
immediately after the option was granted, would be treated as owning stock
possessing five percent or more of the total combined voting power or value of
all classes of stock of the Company or of any parent corporation or subsidiary
corporation, as the terms "parent corporation" and "subsidiary corporation" are
defined in Section 424(e) and (f) of the Code. For purposes of determining stock
ownership under this paragraph, the rules of Section 424(d) of the Code shall
apply, and stock which the employee may purchase under outstanding options shall
be treated as stock owned by the employee.

ARTICLE 4 - STOCK SUBJECT TO THE PLAN.
-------------------------------------

   The stock subject to the options under the Plan shall be shares of the
Company's authorized but unissued Common Stock or shares of Common Stock
reacquired by the Company, including shares purchased in the open market.
The aggregate number of shares which may be issued pursuant to the Plan is
750,000, subject to adjustment as provided in Article 12, which number shall
automatically increase on January 1 of each year, beginning with January 1,
2001, by such number of shares as is equal to the number of shares necessary to
cause the total number of shares then available to be issued pursuant to the
Plan (after deducting shares issued upon exercise of options under the Plan and
shares issuable pursuant to outstanding options under the plan as of the close
of business on the preceding December 31st) to be 750,000. If any option granted
under the Plan shall expire or terminate for any reason without having been
exercised in full or shall cease for any reason to be exercisable in whole or in
part, the unpurchased shares subject thereto shall again be available under the
Plan.

ARTICLE 5 - OFFERING PERIODS, PAYMENT PERIODS AND STOCK OPTIONS.
---------------------------------------------------------------

   Offering Periods during which payroll deductions will be accumulated under
the Plan shall consist of twenty-four month overlapping periods commencing every
six months on January 1st and July 1st of each calendar year (each an "Offering
Period");  provided, however, that the first Offering Period shall commence on
the date on which the Common Stock is first publicly traded (the "Initial Public
Offering") and shall end on the last trading day on or before June 30th 2002
(the "First Offering Period").  Each Offering Period, with the exception of the
First Offering Period, shall consist of four consecutive six-month Payment
Periods (each a "Payment Period");  provided that the First Offering Period will
consist of four Payment Periods, the first commencing on the Initial Public
Offering and ending on December 31st 2000, the second commencing on January 1st
2001 and ending on June 30th 2001, the third commencing on July 1st 2001 and
ending on December 31st 2001 and the fourth commencing on January 1st 2002 and
ending on June 30th 2002.  The Committee shall have the power to change the
duration of Offering Periods and/or Payment Periods (including the commencement
dates thereof) with respect to future offerings without shareholder approval if
such change is announced at least five days prior to the scheduled beginning of
the first Offering Period to be affected thereafter.

   On the first business day of each Offering Period, the Company will grant to
each eligible employee who is then a participant in the Plan an option to
purchase on the last day of each Payment Period within such Offering Period, at
the Option Price hereinafter provided for, a maximum of 1,000 shares, on
condition that such employee remains eligible to participate in the Plan
throughout the respective Payment
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                                      -3-

Period. The participant shall be entitled to exercise the option so granted only
to the extent of the participant's accumulated payroll deductions on the last
day of the respective Payment Period. If the participant's accumulated payroll
deductions on the last day of the Payment Period would enable the participant to
purchase more than 1,000 shares except for the 1,000-share limitation, the
excess of the amount of the accumulated payroll deductions over the aggregate
purchase price of the 1,000 shares shall be promptly refunded to the participant
by the Company, without interest. The Option Price per share for each Payment
Period shall be the lesser of (i) 85% of the average market price of the Common
Stock on the first business day of the Offering Period and (ii) 85% of the
average market price of the Common Stock on the last business day of the
respective Payment Period, in either event rounded up to avoid fractions of a
dollar other than 1/4, 1/2 and 3/4 (the "Option Price"). Provided, however, that
with respect to each Payment Period within the First Offering Period, the Option
Price shall be the lesser of (i) 85% of the price per share at which the Common
Stock is initially sold to the public in the Initial Public Offering (without
regard to any applicable discounts or commissions provided to the underwriters)
and (ii) 85% of the average market price of the Common Stock on the last
business day of the respective Payment Period, in either event rounded up to
avoid fractions of a dollar other than 1/4, 1/2 and 3/4. The foregoing
limitation on the number of shares subject to options and the Option Price shall
be subject to adjustment as provided in Article 12.

   For purposes of the Plan, the term "average market price" on any date means
(i) the average (on that date) of the high and low prices of the Common Stock on
the principal national securities exchange on which the Common Stock is traded,
if the Common Stock is then traded on a national securities exchange; or (ii)
the last reported sale price (on that date) of the Common Stock on the Nasdaq
National Market, if the Common Stock is not then traded on a national securities
exchange; or (iii) the average of the closing bid and asked prices last quoted
(on that date) by an established quotation service for over-the-counter
securities, if the Common Stock is not reported on the Nasdaq National Market.
For purposes of determining the last reported sale price or the last quoted
price for the foregoing provision, the last reported or quoted price shall mean
as the case may be, at 4:00 p.m., New York time, on that day.

   For purposes of the Plan, the term "business day" means a day on which there
is trading on the Nasdaq National Market or the aforementioned national
securities exchange, whichever is applicable pursuant to the preceding
paragraph; and if neither is applicable, a day that is not a Saturday, Sunday or
legal holiday in the Commonwealth of Massachusetts.

   No employee shall be granted an option which permits the employee's right to
purchase stock under the Plan, and under all other Section 423(b) employee stock
purchase plans of the Company and any parent or subsidiary corporations, to
accrue at a rate which exceeds $25,000 of fair market value of such stock
(determined on the date or dates that options on such stock were granted) for
each calendar year in which such option is outstanding at any time.  The purpose
of the limitation in the preceding sentence is to comply with Section 423(b)(8)
of the Code.  If the participant's accumulated payroll deductions on the last
day of the Payment Period would otherwise enable the participant to purchase
Common Stock in excess of the Section 423(b)(8) limitation described in this
paragraph, the excess of the amount of the accumulated payroll deductions over
the aggregate purchase price of the shares actually purchased shall be promptly
refunded to the participant by the Company, without interest.

ARTICLE 6 - EXERCISE OF OPTION.
------------------------------

   Each eligible employee who continues to be a participant in the Plan on the
last day of a Payment Period shall be deemed to have exercised his or her option
on such date and shall be deemed to have purchased from the Company such number
of full shares of Common Stock reserved for the purpose of the Plan as the
participant's accumulated payroll deductions on such date will pay for at the
Option
<PAGE>

                                      -4-

Price, subject to the 1,000-share limit of the option and the Section 423(b)(8)
limitation described in Article 5. If the individual is not a participant on the
last day of a Payment Period, then he or she shall not be entitled to exercise
his or her option. Only full shares of Common Stock may be purchased under the
Plan. Unused payroll deductions remaining in a participant's account at the end
of a Payment Period by reason of the inability to purchase a fractional share
shall be carried forward to the next Payment Period.

ARTICLE 7 - AUTHORIZATION FOR ENTERING THE PLAN.
-----------------------------------------------

   An employee may elect to enter the Plan by filling out, signing and
delivering to the Company an authorization:

       A. Stating the percentage to be deducted regularly from the employee's
   pay;

       B. Authorizing the purchase of stock for the employee in each Payment
   Period in accordance with the terms of the Plan; and

       C. Specifying the exact name or names in which stock purchased for the
   employee is to be issued as provided under Article 11 hereof.

   Such authorization must be received by the Company at least seven days before
the first day of the next succeeding Offering Period and shall take effect only
if the employee is an eligible employee on the first business day of such
Offering Period; provided, however, that the Committee may, in its discretion,
choose to accept an authorization received less than seven days before the first
day of the next succeeding Offering Period.

   Unless a participant files a new authorization or withdraws from the Plan,
the deductions and purchases under the authorization the participant has on file
under the Plan will continue from one Offering Period to the next succeeding
(but not overlapping) Offering Period as long as the Plan remains in effect.
Notwithstanding any of the foregoing, if the average market price of the Common
Stock on the last business day of a respective Payment Period is lower than the
average market price of the Common Stock on the first business day of the
Offering Period, every participant shall be automatically withdrawn from the
Offering Period at the close of such Payment Period and after the acquisition of
shares of Common Stock for such Payment Period, and automatically enrolled in
the immediately following Offering Period as of the first day thereof.

   The Company will accumulate and hold for each participant's account the
amounts deducted from his or her pay.  No interest will be paid on these
amounts.

ARTICLE 8 - MAXIMUM AMOUNT OF PAYROLL DEDUCTIONS.
------------------------------------------------

   An employee may authorize payroll deductions in an amount (expressed as a
whole percentage) not less than one percent (1%) but not more than ten percent
(10%) (unless otherwise determined by the Committee) of the employee's total
compensation, including base pay or salary and any overtime, bonuses or
commissions paid during the Offering Period during which such authorization
relates.
<PAGE>

                                      -5-

ARTICLE 9 - CHANGE IN PAYROLL DEDUCTIONS.
----------------------------------------

   Each participant may increase or decrease the amount of his or her payroll
deduction not more than once during each Payment Period, subject to the
limitations set forth in Article 8, effective on the first day of the next
succeeding Payment Period.  However, a payroll deduction increase or decrease
will be given effect only if in writing and received by the Company seven days
before the first day of the next succeeding Payment Period.  A participant may
withdraw in full from an Offering Period.

ARTICLE 10 - WITHDRAWAL FROM THE PLAN.
-------------------------------------

   A participant may withdraw from the Plan (in whole but not in part) at any
time prior to the last day of a Payment Period by delivering a withdrawal notice
to the Company, in which event the Company will refund the entire balance of the
employee's deductions not previously used to purchase stock during such Offering
Period.

   To re-enter the Plan, an employee who has previously withdrawn must file a
new authorization at least seven days before the first day of the next Offering
Period in which he or she wishes to participate.  The employee's re-entry into
the Plan becomes effective at the beginning of such Offering Period, provided
that he or she is an eligible employee on the first business day of the Offering
Period.

ARTICLE 11 - ISSUANCE OF STOCK.
------------------------------

   Certificates for stock issued to participants shall be delivered as soon as
practicable after each Payment Period by the Company's transfer agent.

   Stock purchased under the Plan shall be issued only in the name of the
participant, or if the participant's authorization so specifies, in the name of
the participant and another person of legal age as joint tenants with rights of
survivorship.

ARTICLE 12 - ADJUSTMENTS.
------------------------

   Upon the happening of any of the following described events, a participant's
rights under options granted under the Plan shall be adjusted as hereinafter
provided:

       A. In the event that the shares of Common Stock shall be subdivided or
   combined into a greater or smaller number of shares or if, upon a
   reorganization, split-up, liquidation, recapitalization or the like of the
   Company, the shares of Common Stock shall be exchanged for other securities
   of the Company, each participant shall be entitled, subject to the conditions
   herein stated, to purchase such number of shares of Common Stock or amount of
   other securities of the Company as were exchangeable for the number of shares
   of Common Stock that such participant would have been entitled to purchase
   except for such action, and appropriate adjustments shall be made in the
   purchase price per share to reflect such subdivision, combination or
   exchange; and

       B. In the event the Company shall issue any of its shares as a stock
   dividend upon or with respect to the shares of stock of the class which shall
   at the time be subject to options hereunder, each participant upon exercising
   such an option shall be entitled to receive (for the purchase price paid upon
   such exercise) the shares as to which the participant is exercising his or
   her option and, in addition thereto (at no additional cost), such number of
   shares of the class or classes in which such stock dividend or dividends were
   declared or paid, and such amount of cash in lieu of fractional shares, as is
   equal to the number of shares thereof and the amount of cash in lieu of
   fractional shares, respectively, which the participant would have received if
   the participant
<PAGE>

                                      -6-

   had been the holder of the shares as to which the participant is exercising
   his or her option at all times between the date of the granting of such
   option and the date of its exercise.

   Upon the happening of any of the foregoing events, the class and aggregate
number of shares set forth in Article 4 hereof which are subject to options
which have been or may be granted under the Plan and the limitations set forth
in the second paragraph of Article 5 shall also be appropriately adjusted to
reflect the events specified in paragraphs A and B above.  Notwithstanding the
foregoing, any adjustments made pursuant to paragraphs A or B shall be made only
after the Committee, based on advice of counsel for the Company, determines
whether such adjustments would constitute a "modification" (as that term is
defined in Section 424 of the Code).  If the Committee determines that such
adjustments would constitute a modification, it may refrain from making such
adjustments.

   If the Company is to be consolidated with or acquired by another entity in a
merger, a sale of all or substantially all of the Company's assets or otherwise
(an "Acquisition"), the Committee or the board of directors of any entity
assuming the obligations of the Company hereunder (the "Successor Board") shall,
with respect to options then outstanding under the Plan, either (i) make
appropriate provision for the continuation of such options by arranging for the
substitution on an equitable basis for the shares then subject to such options
either (a) the consideration payable with respect to the outstanding shares of
the Common Stock in connection with the Acquisition, (b) shares of stock of the
successor corporation, or a parent or subsidiary of such corporation, or (c)
such other securities as the Successor Board deems appropriate, the fair market
value of which shall not materially exceed the fair market value of the shares
of Common Stock subject to such options immediately preceding the Acquisition;
or (ii) terminate each participant's options in exchange for a cash payment
equal to the excess of (a) the fair market value on the date of the Acquisition,
of the number of shares of Common Stock that the participant's accumulated
payroll deductions as of the date of the Acquisition could purchase, at an
option price determined with reference only to the first business day of the
applicable Payment Period and subject to the 1,000-share limitation, Code
Section 423(b)(8) and fractional-share limitations on the amount of stock a
participant would be entitled to purchase, over (b) the result of multiplying
such number of shares by such option price.

   The Committee or Successor Board shall determine the adjustments to be made
under this Article 12, and its determination shall be conclusive.

ARTICLE 13 - NO TRANSFER OR ASSIGNMENT OF EMPLOYEE'S RIGHTS.
-----------------------------------------------------------

   An option granted under the Plan may not be transferred or assigned and may
be exercised only by the participant.

ARTICLE 14 - TERMINATION OF EMPLOYEE'S RIGHTS.
---------------------------------------------

   Whenever a participant ceases to be an eligible employee because of
retirement, voluntary or involuntary termination, resignation, layoff,
discharge, death or for any other reason, his or her rights under the Plan shall
immediately terminate, and the Company shall promptly refund, without interest,
the entire balance of his or her payroll deduction account under the Plan.
Notwithstanding the foregoing, eligible employment shall be treated as
continuing intact while a participant is on military leave, sick leave or other
bona fide leave of absence, for up to 90 days, or, if longer than 90 days, for
so long as the participant's right to re-employment is guaranteed either by
statute or by contract.
<PAGE>

                                      -7-

ARTICLE 15 - TERMINATION AND AMENDMENTS TO PLAN.
-----------------------------------------------

   The Plan may be terminated at any time by the Company's Board of Directors
but such termination shall not affect options then outstanding under the Plan.
It will terminate in any case when all or substantially all of the unissued
shares of stock reserved for the purposes of the Plan have been purchased.
If at any time shares of stock reserved for the purpose of the Plan remain
available for purchase but not in sufficient number to satisfy all then unfilled
purchase requirements, the available shares shall be apportioned among
participants in proportion to the amount of payroll deductions accumulated on
behalf of each participant that would otherwise be used to purchase stock, and
the Plan shall terminate. Upon such termination or any other termination of the
Plan, all payroll deductions not used to purchase stock will be refunded,
without interest.

   The Committee or the Board of Directors may from time to time adopt
amendments to the Plan provided that, without the approval of the stockholders
of the Company, no amendment may (i) increase the number of shares that may be
issued under the Plan; (ii) change the class of employees eligible to receive
options under the Plan, if such action would be treated as the adoption of a new
plan for purposes of Section 423(b) of the Code; or (iii) cause Rule 16b-3 under
the Securities Exchange Act of 1934 to become inapplicable to the Plan.

ARTICLE 16 - LIMITS ON SALE OF STOCK PURCHASED UNDER THE PLAN.
-------------------------------------------------------------

   The Plan is intended to provide shares of Common Stock for investment and not
for resale.  The Company does not, however, intend to restrict or influence any
employee in the conduct of his or her own affairs.  An employee may, therefore,
sell stock purchased under the Plan at any time the employee chooses, subject to
compliance with any applicable federal or state securities laws and subject to
any restrictions imposed under Article 21 to ensure that tax withholding
obligations are satisfied.  THE EMPLOYEE ASSUMES THE RISK OF ANY MARKET
FLUCTUATIONS IN THE PRICE OF THE STOCK.

ARTICLE 17 - PARTICIPATING SUBSIDIARIES.
---------------------------------------

   The term "participating subsidiary" shall mean any present or future
subsidiary of the Company, as that term is defined in Section 424(f) of the
Code, which is designated from time to time by the Board of Directors to
participate in the Plan.  The Board of Directors shall have the power to make
such designation before or after the Plan is approved by the stockholders.

ARTICLE 18 - OPTIONEES NOT STOCKHOLDERS.
---------------------------------------

   Neither the granting of an option to an employee nor the deductions from his
or her pay shall constitute such employee as a stockholder of the shares covered
by an option until such shares have been actually purchased by the employee.

ARTICLE 19 - APPLICATION OF FUNDS.
---------------------------------

   The proceeds received by the Company from the sale of Common Stock pursuant
to options granted under the Plan will be used for general corporate purposes.
<PAGE>

                                      -8-

ARTICLE 20 - NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION.
-----------------------------------------------------------

   By electing to participate in the Plan, each participant agrees to notify the
Company in writing immediately after the participant transfers Common Stock
acquired under the Plan, if such transfer occurs within two years after the
first business day of the Payment Period in which such Common Stock was
acquired.  Each participant further agrees to provide any information about such
a transfer as may be requested by the Company or any subsidiary corporation in
order to assist it in complying with the tax laws.  Such dispositions generally
are treated as "disqualifying dispositions" under Sections 421 and 424 of the
Code, which have certain tax consequences to participants and to the Company and
its participating subsidiaries.

ARTICLE 21 - WITHHOLDING OF ADDITIONAL INCOME TAXES.
---------------------------------------------------

   By electing to participate in the Plan, each participant acknowledges that
the Company and its participating subsidiaries are required to withhold taxes
with respect to the amounts deducted from the participant's compensation and
accumulated for the benefit of the participant under the Plan, and each
participant agrees that the Company and its participating subsidiaries may
deduct additional amounts from the participant's compensation, when amounts are
added to the participant's account, used to purchase Common Stock or refunded,
in order to satisfy such withholding obligations.  Each participant further
acknowledges that when Common Stock is purchased under the Plan the Company and
its participating subsidiaries may be required to withhold taxes with respect to
all or a portion of the difference between the fair market value of the Common
Stock purchased and its purchase price, and each participant agrees that such
taxes may be withheld from compensation otherwise payable to such participant.
It is intended that tax withholding will be accomplished in such a manner that
the full amount of payroll deductions elected by the participant under Article 7
will be used to purchase Common Stock.  However, if amounts sufficient to
satisfy applicable tax withholding obligations have not been withheld from
compensation otherwise payable to any participant, then, notwithstanding any
other provision of the Plan, the Company may withhold such taxes from the
participant's accumulated payroll deductions and apply the net amount to the
purchase of Common Stock, unless the participant pays to the Company, prior to
the exercise date, an amount sufficient to satisfy such withholding obligations.
Each participant further acknowledges that the Company and its participating
subsidiaries may be required to withhold taxes in connection with the
disposition of stock acquired under the Plan and agrees that the Company or any
participating subsidiary may take whatever action it considers appropriate to
satisfy such withholding requirements, including deducting from compensation
otherwise payable to such participant an amount sufficient to satisfy such
withholding requirements or conditioning any disposition of Common Stock by the
participant upon the payment to the Company or such subsidiary of an amount
sufficient to satisfy such withholding requirements.

ARTICLE 22 - GOVERNMENTAL REGULATIONS.
-------------------------------------

   The Company's obligation to sell and deliver shares of Common Stock under the
Plan is subject to the approval of any governmental authority required in
connection with the authorization, issuance or sale of such shares.

   Government regulations may impose reporting or other obligations on the
Company with respect to the Plan.  For example, the Company may be required to
identify shares of Common Stock issued under the Plan on its stock ownership
records and send tax information statements to employees and former employees
who transfer title to such shares.
<PAGE>

                                      -9-

ARTICLE 23 - GOVERNING LAW.
--------------------------

   The validity and construction of the Plan shall be governed by the laws of
Delaware, without giving effect to the principles of conflicts of law thereof.

ARTICLE 24 - APPROVAL OF BOARD OF DIRECTORS AND STOCKHOLDERS OF THE COMPANY.
---------------------------------------------------------------------------

   The Plan was adopted by the Board of Directors on May 3, 2000 and was
approved by the stockholders of the Company on June 28, 2000.
<PAGE>

                              AVICI SYSTEMS INC.

             Amendment No. 1 to 2000 Employee Stock Purchase Plan

                               December 20, 2000

   The 2000 Employee Stock Purchase Plan (the "Plan") is hereby amended as
follows:

1. The first paragraph of Article 5 is hereby deleted its entirety and replaced
with the following

            "Offering Periods during which payroll deductions will
            be accumulated under the Plan shall consist of twenty-
            four month overlapping periods commencing every six
            months on June 1st and December 1st of each calendar
            year (each an "Offering Period"); provided, however,
            that the first Offering Period shall commence on the
            date on which the Common Stock is first publicly traded
            (the "Initial Public Offering") and shall end on the
            last trading day on or before May 31st 2002 (the "First
            Offering Period"). Each Offering Period, with the
            exception of the First Offering Period, shall consist
            of four consecutive six-month Payment Periods (each a
            "Payment Period"); provided that the First Offering
            Period will consist of four Payment Periods, the first
            commencing on the Initial Public Offering and ending on
            December 31/st/ 2000, the second commencing on January
            1/st/ 2001 and ending on May 31st 2001, the third
            commencing on June 1/st/ 2001 and ending on November
            30th 2001 and the fourth commencing on December 1/st/
            2001 and ending on May 31st 2002. The Committee shall
            have the power to change the duration of Offering
            Periods and/or Payment Periods (including the
            commencement dates thereof) with respect to future
            offerings without shareholder approval if such change
            is announced at least five days prior to the scheduled
            beginning of the first Offering Period to be affected
            thereafter."

       In all other respects, the Plan is hereby affirmed and shall remain in
full force and effect.

                         By:    /s/ Surya R. Panditi
                                --------------------
                            Name: Surya R. Panditi
                            Title:   Chief Executive Officer<PAGE>

                                                                    Exhibit 4.19

          SUPPLEMENTAL INDENTURE NO. 1, dated as of May 4, 1999 (the
"Supplemental Indenture"), between CABOT INDUSTRIAL PROPERTIES, L.P., a limited
 ----------------------
partnership duly organized and existing under the laws of the State of Delaware
(herein called the "Operating Partnership"), and THE BANK OF NEW YORK,
                    ---------------------
a New York banking corporation duly organized and existing under the laws of the
State of New York, as Trustee (herein called the "Trustee").
                                                  -------

                     RECITALS OF THE OPERATING PARTNERSHIP

          The Operating Partnership and Cabot Industrial Trust, a company duly
organized and existing under the laws of the State of Maryland (herein called
the "Company"), have heretofore delivered to the Trustee an Indenture dated as
     -------
of April 30, 1999 (the "Original Indenture" and, together with the Supplemental
                        ------------------
Indenture, the "Indenture"), a form of which has been filed with the Securities
                ---------
and Exchange Commission under the Securities Act of 1933, as amended, as an
exhibit to the Operating Partnership's Registration  Statement on Form S-3
(Registration No. 333-71585), providing for the issuance from time to time of
Debt Securities of the Operating Partnership (the "Securities").
                                                   ----------
          Section 301 of the Original Indenture provides for various matters
with respect to any series of Securities issued under the Original Indenture to
be established in an indenture supplemental to the Original Indenture.

          Section 901(7) of the Original Indenture provides for the Operating
Partnership and the Trustee to enter into an indenture supplemental to the
Original Indenture to establish the form or terms of Securities of any series as
provided by Sections 201 and 301 of the Original Indenture.

          The Board of Directors of Cabot Industrial Trust, the general partner
of the Operating Partnership, has duly adopted resolutions authorizing the
Operating Partnership to execute and deliver this Supplemental Indenture.

          All the conditions and requirements necessary to make this
Supplemental Indenture, when duly executed and delivered, a valid and binding
agreement in accordance with its terms and for the purposes herein expressed,
have been performed and fulfilled.

          NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

          For and in consideration of the premises and the purchase of the
series of Debt Securities provided for herein by the Holders thereof, it is
mutually covenanted and agreed, for the equal and proportionate benefit of all
Holders of the Notes (as defined) or of either series thereof, as follows:
<PAGE>

                                  ARTICLE ONE

                  RELATION TO ORIGINAL INDENTURE; DEFINITIONS

          Section 1.1  RELATION TO ORIGINAL INDENTURE.
          This Supplemental Indenture constitutes an integral part of the
          Original Indenture.

          Section 1.2  DEFINITIONS.
          For all purposes of this Supplemental Indenture, except as otherwise
expressly provided for or unless the context otherwise requires:

          (1)  capitalized terms used but not defined herein shall have the
               respective meanings assigned to them in the Original Indenture;
               and

          (2)  all references herein to Articles and Sections, unless otherwise
               specified, refer to the corresponding Articles and Sections of
               this Supplemental Indenture.

          "Acquired Indebtedness" means Indebtedness of a Person (i) existing at
           ---------------------
the time such Person becomes a Subsidiary or (ii) assumed in connection with the
acquisition of assets from such Person other than, in each case, Indebtedness
incurred in connection with, or in contemplation of, such Person becoming a
Subsidiary or such acquisition.  Acquired Indebtedness shall be deemed to be
incurred on the date of the related acquisition of assets from any Person or the
date the acquired Person becomes a Subsidiary.

          "Adjusted Treasury Rate," with respect to any Redemption Date, is the
           ----------------------
rate per annum equal to the semi-annual bond equivalent yield to maturity of the
Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue,
expressed as a percentage of its principal amount, equal to the Comparable
Treasury Price for such Redemption Date.

          "Annual Debt Service Charge" means, for any period, the aggregate
           --------------------------
interest expense for such period in respect of, and the amortization during such
period of any original issue discount of, Indebtedness of the Operating
Partnership and its Subsidiaries and the amount of dividends which are payable
during the period in respect of Disqualified Stock.

          "Business Day" means any day, other than a Saturday or Sunday, that is
           ------------
neither a legal holiday nor a day on which banking institutions in the The City
of New York or the City of Boston are authorized or required by law, regulation
or executive order to close.

          "Capital Stock" means, with respect to any Person, any capital stock
           -------------
(including preferred stock), shares, interests, participations or other
ownership interests (however designated) of such Person and any rights (other
than debt securities convertible into or exchangeable for corporate stock),
warrants or options to purchase any thereof.

          "Comparable Treasury Issue" means the United States Treasury security
           -------------------------
selected by the Quotation Agent as having a maturity comparable to the remaining
term of the Notes to be redeemed that would be utilized, at the time of
selection and in accordance with customary

                                       2
<PAGE>

financial practice, in pricing new issues of corporate debt securities of
comparable maturity to the remaining term of such Notes.

          "Comparable Treasury Price" means, with respect to any Redemption
           -------------------------
Date, (a) the average of the Reference Treasury Dealer Quotations for that
Redemption Date, after excluding the highest and lowest Reference Treasury
Dealer Quotations obtained, or (b) if the Trustee obtains fewer than three
Reference Treasury Dealer Quotations, the average of all such quotations.

          "Consolidated Income Available for Debt Service" for any period means
           ----------------------------------------------
Earnings from Operations of the Operating Partnership and its Subsidiaries plus
amounts which have been deducted, and minus amounts which have been added, for
the following (without duplication):  (i) interest on Indebtedness of the
Operating Partnership and its Subsidiaries; (ii) provision for taxes of the
Operating Partnership and its Subsidiaries based on income; (iii) amortization
of debt discount and deferred financing costs; (iv) provisions for gains and
losses on properties and property depreciation and amortization; (v) increases
in deferred taxes and other non-cash items; (vi) the effect of any non-cash
charge resulting from a change in accounting principles in determining Earnings
from Operations for such period; (vii) amortization of deferred charges; and
(viii) interest income related to investments irrevocably deposited with an
agent of the Operating Partnership or any of its Subsidiaries, as the case may
be, for the purpose of an "in substance" defeasance in accordance with GAAP of
any indebtedness or other obligations.

          "Corporate Trust Office" means the office of the Trustee at which, at
           ----------------------
any particular time, its corporate trust business is principally administered,
which office at the date hereof is located at 101 Barclay Street, New York, New
York 10286, Attention: Corporate Trust Administration and, for purposes of the
Place of Payment provisions of Section 305 and 1002 of the Original Indenture,
is located at 101 Barclay Street, New York New York 10286, Attention: Corporate
Trust Administration.

          "Disqualified Stock" means, with respect to any Person, any Capital
           ------------------
Stock of such Person which by the terms of such Capital Stock (or by the terms
of any security into which it is convertible or for which it is exchangeable or
exercisable), upon the happening of any event or otherwise:  (i) matures or is
mandatorily redeemable, pursuant to a sinking fund obligation or otherwise
(other than Capital Stock which is redeemable solely in exchange for Capital
Stock which is not Disqualified Stock or the maturity price or redemption price
of which may, at the option of such Person, be paid in Capital Stock which is
not Disqualified Stock); (ii) is convertible into or exchangeable or exercisable
for Indebtedness or Disqualified Stock; or (iii) is redeemable at the option of
the holder thereof, in whole or in part (other than Capital Stock which is
redeemable solely in exchange for Capital Stock which is not Disqualified Stock
or the redemption price of which may, at the option of such Person, be paid in
Capital Stock which is not Disqualified Stock), in each case on or prior to the
stated maturity of the Notes.

          "Earnings from Operations" for any period means net income excluding
           ------------------------
(i) provisions for gains and losses on sales of investments; (ii) extraordinary
and non-recurring items; and (iii) property valuation losses, each as reflected
in the consolidated financial statements of the Operating Partnership and its
Subsidiaries for such period determined in accordance with GAAP.

                                       3
<PAGE>

          "Encumbrance" means any mortgage, lien, charge, pledge or security
           -----------
interest of any kind; provided, however, that the term "Encumbrance" shall not
                      --------  -------
include any mortgage, lien, charge, pledge or security interest securing any
indebtedness or any other obligation which has been the subject of an "in
substance" defeasance in accordance with GAAP pursuant to the terms of such
indebtedness or other obligation on the terms of any instrument creating or
evidencing it.

          "Exchange Act" means the Securities Exchange Act of 1934, as amended,
           ------------
and the rules and regulations promulgated thereunder by the Commission.

          "Indebtedness" of the Operating Partnership or any Subsidiary of the
           ------------
Operating Partnership means any indebtedness of the Operating Partnership or any
such Subsidiary, whether or not contingent, in respect of:  (i) borrowed money
or evidenced by bonds, notes, debentures or similar instruments, whether or not
such indebtedness is secured by any Encumbrance existing on property owned by
the Operating Partnership or any Subsidiary of the Operating Partnership; (ii)
indebtedness for borrowed money of a Person other than the Operating Partnership
or a Subsidiary of the Operating Partnership which is secured by any Encumbrance
existing on property owned by the Operating Partnership or any Subsidiary of the
Operating Partnership, to the extent of the lesser of (x) the amount of
indebtedness so secured and (y) the fair market value of the property subject to
such Encumbrance; (iii) the reimbursement obligations, contingent or otherwise,
in connection with any letters of credit actually issued or amounts representing
the balance deferred and unpaid of the purchase price of any property or
services, except any such balance that constitutes an accrued expense or trade
payable, and all conditional sale obligations and all obligations under any
title retention agreement; (iv) the principal amount of all of the Operating
Partnership's and any Operating Partnership Subsidiary's obligations with
respect to the redemption or other repurchase of any Disqualified Stock; or (v)
any lease of property by the Operating Partnership or any Subsidiary of the
Operating Partnership as lessee which is reflected on the Operating
Partnership's consolidated balance sheet as a capitalized lease in accordance
with GAAP; and also includes, to the extent not otherwise included, any
obligation by the Operating Partnership or any Subsidiary of the Operating
Partnership to be liable for, or to pay, as obligor, guarantor or otherwise
(other than for purposes of collection in the ordinary course of business),
Indebtedness of another Person (other than the Operating Partnership or any
Subsidiary of the Operating Partnership); it being understood that indebtedness
shall be deemed to be incurred by the Operating Partnership or any Subsidiary of
the Operating Partnership whenever the Operating Partnership or such Subsidiary
shall create, assume, guarantee or otherwise become liable in respect thereof;
Indebtedness of a Subsidiary of the Operating Partnership existing prior to the
time it became a Subsidiary of the Operating Partnership shall be deemed to be
incurred upon such Subsidiary's becoming a Subsidiary of the Operating
Partnership; and Indebtedness of a Person existing prior to a merger or
consolidation of such Person with the Operating Partnership or any Subsidiary of
the Operating Partnership in which such Person is the successor to the Operating
Partnership or such Subsidiary shall be deemed to be incurred upon the
consummation of such merger or consolidation; provided, however, that the term
                                              --------  -------
"Indebtedness" shall not  include any such indebtedness that has been the
subject of an "in substance" defeasance in accordance with GAAP pursuant to the
terms of such Indebtedness or other obligation on the terms of any instrument
creating or evidencing it.

                                       4
<PAGE>

          "Intercompany Indebtedness" means Indebtedness to which the only
           -------------------------
parties are the Operating Partnership, the Company and any Subsidiary of either
of them (but only so long as such Indebtedness is held solely by any of the
Operating Partnership, the Company and any such Subsidiary) that is subordinate
in right of payment to the Notes.

          "Notes" has the meaning specified in Section 2.1 hereof.
           -----

          "Quotation Agent" means the Reference Treasury Dealer appointed by the
           ---------------
Operating Partnership.

          "Reference Treasury Dealer" means (a) each of J.P. Morgan Securities
           -------------------------
Inc., Goldman, Sachs & Co., Merrill Lynch, Pierce, Fenner, & Smith Incorporated,
PNC Capital Markets, Inc., Prudential Securities Incorporated, and Salomon Smith
Barney Inc. and their respective successors; provided, however, that if any of
                                             --------  -------
the foregoing shall cease to be primary U.S. Government securities dealers in
New York City, the Operating Partnership shall substitute therefor another
primary U.S. Government securities dealer in New York City; and (b) any other
primary U.S. Government securities dealer selected by the Operating Partnership.

          "Reference Treasury Dealer Quotations"  means, with respect to each
           ------------------------------------
Reference Treasury Dealer  and any Redemption Date, the average, as determined
by the Operating Partnership, of the bid and asked prices for the Comparable
Treasury Issue, expressed in each case as a percentage of its principal amount,
quoted in writing to the Trustee by such Reference Treasury Dealer at 5:00 p.m.,
New York City time, on the third Business Day preceding such Redemption Date.

          "Total Assets" as of any date means the sum of (i) the Undepreciated
           ------------
Real Estate Assets and (ii) all other assets of the Operating Partnership and
its Subsidiaries determined in accordance with GAAP (but excluding accounts
receivable and intangibles); provided, however, that the term "Total Assets"
                             --------  -------
shall not include any assets which have been deposited in trust in connection
with an "in substance" defeasance of any indebtedness or other obligations.

          "Total Unencumbered Assets" means the sum of (i) those Undepreciated
           -------------------------
Real Estate Assets not subject to an Encumbrance for borrowed money and (ii) all
other assets of the Operating Partnership and its Subsidiaries not subject to an
Encumbrance for borrowed money, determined in accordance with GAAP (but
excluding accounts receivable and intangibles); provided, however, that the term
                                                --------  -------
"Total Unencumbered Assets" does not include any assets which have been
deposited in trust in connection with an "in substance" defeasance of any
indebtedness or other obligations.

          "Undepreciated Real Estate Assets" as of any date means the cost
           --------------------------------
(historical cost plus the cost of capital improvements) of real estate assets of
the Operating Partnership and its Subsidiaries on such date, before depreciation
and amortization, determined on a consolidated basis in accordance with GAAP.

          "Unsecured Indebtedness" means Indebtedness which is not secured by
           ----------------------
any Encumbrance upon any of the properties of the Operating Partnership or any
Subsidiary.

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<PAGE>

                                  ARTICLE TWO

                              THE SERIES OF NOTES

          Section 2.1  TITLE OF THE SECURITIES.
          There shall be a series of Securities designated the "7.125%
Redeemable Notes due 2004" (the "Notes").
                                 -----

          Section 2.2  LIMITATION ON AGGREGATE PRINCIPAL AMOUNT.

          The aggregate principal amount of the Notes shall be limited to
$200,000,000, and, except as provided in this Section and in Section 306 of the
Original Indenture, the Operating Partnership shall not execute and the Trustee
shall not authenticate or deliver Notes in excess of such aggregate principal
amount.

          Nothing contained in this Section 2.2 or elsewhere in this
Supplemental Indenture, or in the Notes, is intended to or shall limit execution
by the Operating Partnership or authentication or delivery by the Trustee of
Notes under the circumstances contemplated by Sections 303, 304, 305, 306, 906,
1107 and 1305 of the Original Indenture.

          Section 2.3 INTEREST AND INTEREST RATES; MATURITY DATE OF NOTES.

          The Notes will bear interest at a rate of 7.125% per annum from May 4,
1999 or from the immediately preceding Interest Payment Date to which interest
has been paid or duly provided for, payable semiannually in arrears on May 1 and
November 1 of each year, commencing on November 1, 1999 (each, an "Interest
                                                                   --------
Payment Date"), and, if not otherwise an Interest Payment Date, at the Stated
------------
Maturity, to the Person in whose name such Notes are registered in the Security
Register at the close of business on April 15 or October 15 (whether or not a
Business Day), as the case may be, next preceding such Interest Payment Date
(each, a "Regular Record Date").  Interest will be computed on the basis of a
          -------------------
360-day year comprised of twelve 30-months.  The interest so payable on any Note
which is not punctually paid or duly provided for on any Interest Payment Date
shall forthwith cease to be payable to the Person in whose name such Note is
registered on the relevant Regular Record Date, and such defaulted interest
shall instead be payable to the Person in whose name such Note is registered on
the Special Record Date or other specified date determined in accordance with
the Original Indenture.

          If any Interest Payment Date or Stated Maturity falls on a day that is
not a Business Day, the required payment shall be made on the next Business Day
as if it were made on the date such payment was due and no interest shall accrue
on the amount so payable for the period from and after such Interest Payment
Date or Maturity as the case may be.

          The Notes will mature on May 1, 2004.

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<PAGE>

          Section 2.4  LIMITATIONS ON INCURRENCE OF INDEBTEDNESS.

          (a) The Operating Partnership will not, and will not permit any of its
Subsidiaries to, incur any Indebtedness, other than Intercompany Indebtedness,
if, immediately after giving effect to the incurrence of such additional
Indebtedness and the application of the proceeds thereof, the aggregate
principal amount of all outstanding Indebtedness of the Operating Partnership
and its Subsidiaries on a consolidated basis determined in accordance with GAAP
would be greater than 60% of the sum of (without duplication) (i) the Total
Assets of the Operating Partnership and its Subsidiaries as of the end of the
calendar quarter covered in the Operating Partnership's Annual Report on
Form 10-K or Quarterly Report on Form 10-Q, as the case may be, most recently
filed with the Commission (or, if such filing is not permitted under the
Exchange Act, then, subject to Section 703 of the Original Indenture, with the
Trustee, or if the Operating Partnership has not yet filed its first quarterly
report on Form 10-Q, then as of December 31, 1998) prior to the incurrence of
such additional Indebtedness and (ii) the purchase price of any real estate
assets or mortgage loans receivable acquired, and the amount of any securities
offering proceeds received (to the extent such proceeds were not used to acquire
real estate assets or mortgage loans receivable or used to reduce Indebtedness),
by the Operating Partnership or any of its Subsidiaries since the end of such
calendar quarter, including those proceeds obtained in connection with the
incurrence of such additional Indebtedness.

          (b) The Operating Partnership will not, and will not permit any of its
Subsidiaries to, incur any Indebtedness if the ratio of Consolidated Income
Available for Debt Service to the Annual Debt Service Charge for the four
consecutive fiscal quarters most recently ended prior to the date on which such
additional Indebtedness is to be incurred shall have been less than 1.5:1 on a
pro forma basis after giving effect thereto and to the application of the
--- -----
proceeds therefrom and calculated on the assumption that (i) such Indebtedness
and any other Indebtedness incurred by the Operating Partnership and its
Subsidiaries since the first day of such four-quarter period and the application
of the proceeds therefrom, including to refinance other Indebtedness, had
occurred at the beginning of such period; (ii) the repayment or retirement of
any other Indebtedness by the Operating Partnership and its Subsidiaries since
the first day of such four-quarter period had been repaid or retired at the
beginning of such period (except that, in making such computation, the amount of
Indebtedness under any revolving credit facility shall be computed based upon
the average daily balance of such Indebtedness during such period); (iii) in the
case of Acquired Indebtedness or Indebtedness incurred in connection with any
acquisition since the first day of such four-quarter period, the related
acquisition had occurred as of the first day of such period with the appropriate
adjustments with respect to such acquisition being included in such pro forma
                                                                    --- -----
calculation; and (iv) in the case of any acquisition or disposition by the
Operating Partnership or its Subsidiaries of any asset or group of assets since
the first day of such four-quarter period, whether by merger, stock purchase or
sale, or asset purchase or sale, such acquisition or disposition or any related
repayment of Indebtedness had occurred as of the first day of such period with
the appropriate adjustments with respect to such acquisition or disposition
being included in such pro forma calculation.
                       --- -----

          (c) The Operating Partnership will not, and will not permit any of its
Subsidiaries to, incur any Indebtedness secured by any Encumbrance on or in any
of the property of the Operating Partnership or any of its Subsidiaries, whether
owned at the date of this Supplemental Indenture or thereafter acquired, if,
immediately after giving effect to the

                                       7
<PAGE>

incurrence of such additional Indebtedness and the application of the proceeds
thereof, the aggregate principal amount of all outstanding Indebtedness of the
Operating Partnership and its Subsidiaries on a consolidated basis which is
secured by any Encumbrance on property of the Operating Partnership or any of
its Subsidiaries would be greater than 40% of the sum of (without duplication)
(i) the Total Assets of the Operating Partnership and its Subsidiaries as of the
end of the calendar quarter covered in the Operating Partnership's Annual Report
on Form 10-K or Quarterly Report on Form 10-Q, as the case may be, most recently
filed with the Commission (or, if such filing is not permitted under the
Exchange Act, then with the Trustee, or if the Operating Partnership has not yet
filed its first quarterly report on Form 10-Q, then as of December 31, 1998)
prior to the incurrence of such additional Indebtedness and (ii) the purchase
price of any real estate assets or mortgage loans receivable acquired, and the
amount of any securities offering proceeds received (to the extent such proceeds
were not used to acquire real estate assets or mortgage loans receivable or used
to reduce Indebtedness), by the Operating Partnership or any of its Subsidiaries
since the end of such calendar quarter, including those proceeds obtained in
connection with the incurrence of such additional Indebtedness.

         (d) The Operating Partnership and its Subsidiaries must at all times
have Total Unencumbered Assets equal to 150% or more of the aggregate
outstanding principal amount of the Unsecured Indebtedness of the Operating
Partnership and its Subsidiaries on a consolidated basis.

          Section 2.5  REDEMPTION.

          The Notes may be redeemed at any time at the option of the Operating
Partnership, in whole or in part, at a redemption price equal to the greater of
(i) 100% of the principal amount of the Notes to be redeemed plus accrued and
unpaid interest thereon to the Redemption Date and (ii) an amount equal to the
sum of the present values of the remaining scheduled payments of principal and
interest on the Notes to be redeemed (not including any portion of such payments
of interest accrued as of the Redemption Date) discounted to the Redemption Date
on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day
months) at the Adjusted Treasury Rate plus 25 basis points (the "Redemption
                                                                 ----------
Price") plus accrued and unpaid interest thereon to the Redemption Date.
-----

          Section 2.6  PLACE OF PAYMENT.

          The Places of Payment where the Notes may be presented or surrendered
for payment, where the Notes may be surrendered for registration of transfer or
exchange and where notices and demands to and upon the Operating Partnership in
respect of the Notes and the Indenture may be served shall be in the Borough of
Manhattan, The City of New York, New York, and the office or agency for such
purpose shall initially be located at 101 Barclay Street, New York, New York
10286.

          Section 2.7  METHOD OF PAYMENT.

          Payment of the principal of and interest on any Notes not represented
by a global security will be made at the Corporate Trust Office maintained for
that purpose in the Borough of Manhattan, The City of New York, New York, in
such coin or currency of the United States

                                       8
<PAGE>

of America as at the time of payment is legal tender for payment of public and
private debts; provided, however, that at the option of the Operating
               --------  -------
Partnership, payments of interest on the Notes may be made (i) by check mailed
to the address of the Person entitled thereto as such address shall appear in
the Security Register or (ii) by wire transfer to an account maintained by the
Person entitled thereto located within the United States.

          Section 2.8  CURRENCY.
          Principal and interest on the Notes shall be payable in Dollars.

          Section 2.9  REGISTERED SECURITIES; GLOBAL FORM.

          The Notes shall be issuable and transferable in fully registered form
as Registered Securities, without coupons.  The Notes shall be issued in the
form of one or more permanent global securities.  The depository for the Notes
shall be The Depository Trust Company ("DTC").  The Notes shall not be issuable
in definitive form except as provided in Section 305 of the Original Indenture.

          Section 2.10  FORM OF NOTES.
          The Notes shall be substantially in the form attached as Exhibit A
hereto.

          Section 2.11  REGISTRAR AND PAYING AGENT.
          The Trustee shall initially serve as Security Registrar and Paying
Agent for the Notes.

          Section 2.12  DEFEASANCE.

          The provisions of Sections 1402 and 1403 of the Original Indenture,
together with the other provisions of Article Fourteen of the Original
Indenture, shall be applicable to the Notes.  The provisions of Section 1403 of
the Original Indenture shall apply to the covenants set forth in Sections 2.4
and 2.15 of this Supplemental Indenture and to those covenants specified in
Section 1403 of the Original Indenture.

          Section 2.13  ACCELERATION OF MATURITY.

          Upon acceleration of the Stated Maturity of the Notes in accordance
with Section 502 of the Original Indenture, the Holders of the Notes shall be
entitled to receive, from the Operating Partnership, an amount equal to the
Redemption Price set forth in Section 2.5 of this Supplemental Indenture,
determined as if a redemption had occurred on the same date as the Event of
Default.

          Section 2.14  WAIVER OF CERTAIN COVENANTS.

          Notwithstanding the provisions of Section 1011 of the Original
Indenture, the Operating Partnership may omit in any particular instance to
comply with any term, provision or condition set forth in the Original Indenture
and in this Supplemental Indenture and with any

                                       9
<PAGE>

other term, provision or condition with respect to the Notes (except any such
term, provision or condition which could not be amended without the consent of
all Holders of the Notes or such series thereof, as applicable), if before or
after the time for such compliance the Holders of at least a majority in
principal amount of all Outstanding Notes, by Act of such Holders, either waive
such compliance in such instance or generally waive compliance with such
covenant or condition. Except to the extent so expressly waived, and until such
waiver shall become effective, the obligations of the Operating Partnership and
the duties of the Trustee in respect of any such term, provision or condition
shall remain in full force and effect.

          Section 2.15  NO GUARANTY BY THE CORPORATION.
          The Guarantee set forth in Article Sixteen of the Original Indenture
shall not be in effect with respect to the Notes.

                                 ARTICLE THREE

                           MISCELLANEOUS PROVISIONS

          Section 3.1  RATIFICATION OF ORIGINAL INDENTURE.
          Except as expressly modified or amended hereby, the Original Indenture
continues in full force and effect and is in all respects confirmed and
preserved.

          Section 3.2  GOVERNING LAW.

          This Supplemental Indenture and each Note shall be governed by and
construed in accordance with the laws of the State of New York.  This
Supplemental Indenture is subject to the provisions of the Trust Indenture Act
of 1939, as amended, and shall, to the extent applicable, be governed by such
provisions.

          Section 3.3  COUNTERPARTS.

          This Supplemental Indenture may be executed in any number of
counterparts, each of which so executed shall be deemed to be an original, but
all such counterparts shall together constitute but one and the same instrument.

          Section 3.4  CERTAIN RIGHTS OF TRUSTEE.

          Except as otherwise expressly provided herein, no duties,
responsibilities or liabilities are assumed, or shall be construed to be
assumed, by the Trustee by reason of this Supplemental Indenture.  This
Supplemental Indenture is executed and accepted by the Trustee subject to all
the terms and conditions set forth in the Original Indenture with the same force
and effect as if those terms and conditions were repeated at length herein and
made applicable to the Trustee with respect hereto.

                                       10
<PAGE>

          Section 3.5  TRUSTEE NOT RESPONSIBLE.

          The Trustee shall not be responsible in any manner for or in respect
of the validity or sufficiency of this Supplemental Indenture.

                                       11
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed by their respective officers thereunto duly
authorized, all as of the day and year first written above.

                              CABOT INDUSTRIAL PROPERTIES, L.P.

                              By:   Cabot Industrial Trust, its General Partner

                              By: /s/ Ferdinand Colloredo-Mansfeld
                                  ---------------------------------------------
                                  Name:  Ferdinand Colloredo-Mansfeld

                                  Title: Chairman of the Board and
                                         Chief Executive officer
Attest:

By:  /s/ Neil E. Waisnor
    -----------------------------

Name:   Neil E. Waisnor

Title:  Senior Vice President-Finance,
        Treasurer and Secretary
        Chief Accounting Officer

                                      S-1

<PAGE>

                              THE BANK OF NEW YORK, AS TRUSTEE

                              By:  /s/  The Bank of New York
                                  --------------------------------------
                                  Name:
                                  Title:

                                      S-2

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