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                                                                   Exhibit 10.2


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                    AMENDMENT NO. 1 TO THE GUARANTY AGREEMENT


                          Dated as of October 31, 1997


                        (amending the Guaranty Agreement
                         dated as of December 13, 1995)


                                     between


                        FORE SYSTEMS HOLDING CORPORATION,

                                  as Guarantor


                    MELLON FINANCIAL SERVICES CORPORATION #4,

                               as Tranche B Lender

                                       and

                               MELLON BANK, N.A.,

                               as Tranche A Lender





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                    AMENDMENT NO. 1 TO THE GUARANTY AGREEMENT



     THIS AMENDMENT NO. 1 TO THE GUARANTY AGREEMENT dated as of October 31, 1997
(this "Amendment"), among FORE SYSTEMS HOLDING CORPORATION, a Delaware
corporation, as Guarantor (hereunder the "Guarantor"); MELLON FINANCIAL SERVICES
CORPORATION #4, a Pennsylvania corporation, as the Tranche B Lender (the
"Tranche B Lender"); and MELLON BANK, N.A., a national banking association
("Mellon"), as Tranche A Lender (the "Tranche A. Lender").


                              W I T N E S S E T H:


     WHEREAS, Lessor, the Tranche A Lender, the Tranche B Lender and the
Borrower intend to enter into a certain Amended and Restated Term Loan
Agreement, dated as of October 31, 1997 (the "Loan Agreement");

     WHEREAS, the Guarantor has duly authorized the execution, delivery and
performance of this Amendment; and

     WHEREAS, it is in the best interests of the Guarantor to execute this
Amendment inasmuch as the Guarantor will derive substantial benefits from the
transactions contemplated by the Refinancing Loan Documents;

     NOW, THEREFORE, in consideration of the mutual terms and conditions herein
contained, the parties hereto, intending to be legally bound hereby, agree as
follows:


                                    ARTICLE I

                                   DEFINITIONS

     SECTION 1.1. Use of Defined Terms; Rules of Usage. Unless otherwise defined
or the context otherwise requires, terms for which meanings are provided in
Appendix I to the Participation Agreement (as amended by Amendment No. 1 to the
Participation Agreement, dated as of October 31, 1997) shall have such meanings
when used in this Amendment. The rules of interpretation set forth in Appendix I
to the Participation Agreement shall apply to this Amendment.

     SECTION 1.2. Certain Defined Terms. The following terms (whether or not
underscored) when used in this Amendment, including its preamble and recitals,
shall, except 



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where the context otherwise requires, have the following meanings
(such meanings to be equally applicable to the singular and plural forms
thereof):

     "Amendment" is defined in the preamble.

     "Amendment No. 1 to the Participation Agreement" means that certain
Amendment No. 1 to the Participation Agreement dated as of October 31, 1997
among FORE Systems, Inc., a Delaware corporation, as Lessee, Guarantor and
Construction Agent; Wilmington Trust Company, not in its individual capacity,
except as expressly stated therein, but solely as trustee of Brush Creek
Business Trust, a Delaware business trust, as Lessor and Certificate Trustee;
Mellon Financial Services Corporation #4, a Pennsylvania corporation, as the
Certificate Purchaser and Tranche B Lender; and Mellon Bank, N.A., a national
banking association, as Construction Lender and Tranche A Lender.

     "Guaranty Agreement" means that certain Guaranty Agreement dated as of
December 13, 1995 is made by FORE Systems Holding Corporation, a Delaware
corporation, the Guarantor, in favor of Mellon Bank, N.A., as Construction
Lender (together with the various financial institutions which may from time to
time become lenders under the construction loan agreement referred to therein,
and in the event of a refinancing, the Tranche A Lender and the Tranche B Lender
and Mellon Financial Services Corporation #4, as Certificate Purchaser (together
with its successors and assigns in such capacity).

     "Participation Agreement" means that certain Participation Agreement dated
as of December 13, 1995, entered into by and among FORE Systems, Inc., a
Delaware corporation, as Lessee, Guarantor and Construction Agent; Wilmington
Trust Company, not in its individual capacity, except as expressly stated
therein, but solely as trustee of Brush Creek Business Trust, a Delaware
business trust, as Lessor and Certificate Trustee; Mellon Financial Services
Corporation #4, a Pennsylvania corporation, as the Certificate Purchaser; and
Mellon Bank, N.A., a national banking association, as Construction Lender.


                                   ARTICLE II

                                   AMENDMENTS

     SECTION 2.1. Amendment to Article I of the Guaranty Agreement.

     (a) The following definition contained in Section 1.1 of the Guaranty
Agreement is hereby amended and restated to read in its entirety as follows:

     "Obligations" means all of the following, in each case howsoever created,
arising or evidenced, whether direct or indirect, joint or several, absolute or
contingent, or now or hereafter existing, or due or to become due: all principal
of the Note, interest accrued thereon, the Certificate Amount, Certificate Yield
accrued thereon and all additional amounts and other sums at any time due and
owing, and required to be paid, to the Participants by the Certificate Trustee
under the terms of the Loan Agreement, the Note or any other Operative Documents
and, in the event of a Refinancing, to the Tranche A Lenders and the Tranche B
Lender under any 


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Refinancing Loan Document; provided however, except for the representations and
warranties of Guarantor provided herein, the liability of the Guarantor
hereunder shall be strictly limited to the amount of the collateral required to
be pledged by the Guarantor under (i) the Amended and Restated Pledge and
Security Agreement and (ii) Pledge and Security Agreement-B (Refinancing), as
applicable, from time to time; provided further, that the aggregate liability of
the Guarantor hereunder and Lessee under the Guaranty for the principal amount
of the Note outstanding at any time during the Interim Term guaranteed by this
Guaranty Agreement and the Guaranty shall not exceed 86.6% of the then
outstanding aggregate of the principal amount of the Note and the Certificate
Amount at such time; and provided further, that with respect to an exercise of
the Remarketing Option pursuant to Section 20.1 of the Lease, the amount
guaranteed under this Guaranty shall not exceed the aggregate amounts Lessee is
required to pay under the Lease and the other Operative Documents.


                                   ARTICLE III

                            MISCELLANEOUS PROVISIONS

     SECTION 3.1. Ratification of and References to the Guaranty Agreement. This
Amendment shall be deemed to be an amendment to the Guaranty Agreement, and the
guaranty Agreement, as amended hereby, is hereby ratified, approved and
confirmed in each and every respect. All references to the Guaranty Agreement in
any Operative Document or any other document, instrument, agreement or writing
shall hereafter be deemed to refer to the Guaranty Agreement as amended hereby.

     SECTION 3.2. Counterparts. This Amendment may be executed by the parties
hereto in separate counterparts, each of which when so executed and delivered
shall be an original, but all such counterparts shall together constitute but
one and the same instrument.

     SECTION 3.3. Captions. Section captions used in this Amendment are inserted
for convenience of reference only and shall not affect the construction of this
Amendment or any provisions hereof.

     SECTION 3.4 Governing Law; Entire Agreement. THIS AMENDMENT AND EACH OTHER
REFINANCING LOAN DOCUMENT EXECUTED IN CONNECTION HEREWITH SHALL GOVERNED BY AND
CONSTRUED UNDER THE LAWS OF THE COMMONWEALTH OF PENNSYLVANIA WITHOUT REGARD TO
CONFLICT OF LAW PRINCIPLES. This Amendment and the other Refinancing Loan
Documents executed in connection herewith constitute the entire understanding
among the parties hereto with respect to the subject matter hereof and supersede
any prior agreements, written or oral, with respect thereto.



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     IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1 to
the Guaranty to be executed by their respective officers thereunto duly
authorized as of the day and year first above written.


                                         FORE SYSTEMS HOLDING CORPORATION


                                         By:    /s/ THOMAS J. GILL
                                             ---------------------------------
                                             Name:  Thomas J. Gill
                                             Title: Treasurer



                                         MELLON FINANCIAL SERVICES
                                         CORPORATION NO. #4


                                         By:    /s/ STEPHEN R. VIEHE
                                             ---------------------------------
                                             Name:  Stephen R. Viehe
                                             Title: Vice President



                                         MELLON BANK, N.A.


                                         By:    /s/ BRIAN CIAVERELLA
                                             ---------------------------------
                                             Name:  Brian Ciaverella
                                             Title: Vice President