<PAGE>
 
  As filed with the Securities and Exchange Commission on September 15, 1998

                                                         File No. 333-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                               ----------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                     Under
                           THE SECURITIES ACT OF 1933
 
                               ----------------

                            CABLETRON SYSTEMS, INC.
             (Exact name of registrant as specified in its charter)

                DELAWARE                              04-2797263
      (State or other jurisdiction                 (I.R.S. Employer
    of incorporation or organization)             Identification No.)


                               35 INDUSTRIAL WAY
                        ROCHESTER, NEW HAMPSHIRE  03867
          (Address of principal executive offices, including zip code)

                               ----------------

                     FLOWPOINT CORP. 1994 STOCK OPTION PLAN
                       ---------------------------------
                            (Full title of the plan)

                             David J. Kirkpatrick
                     Corporate Executive Vice President and
                            Chief Financial Officer
                            Cabletron Systems, Inc.
                               35 Industrial Way
                        Rochester, New Hampshire  03867
                                 (603) 332-9400
--------------------------------------------------------------------------------
(Name, Address and Telephone Number, including Area Code, of Agent for Service)


                        CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------
                                                Proposed             Proposed
                                                 maximum              maximum         Amount of
Title of securities to be    Amount to be  offering price per   aggregate offering   registration
 registered                   registered        share (1)            price (1)           fee
-------------------------------------------------------------------------------------------------
<S>                      <C>               <C>                  <C>                  <C>
Common Stock,
 par value $0.01
                            493,970 shares        $0.27            $133,371.90         $39.34
-------------------------------------------------------------------------------------------------
</TABLE>

/(1)/ The maximum aggregate offering price for the shares of Cabletron Systems,
Inc. common stock, par value $0.01, offered hereby is based on the weighted
average per share exercise price of the options pursuant to which such shares
may be issued.


================================================================================
                            Exhibit Index on page 7.
<PAGE>
 
                                    PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

The Registrant hereby incorporates the following documents herein by reference:

(a) The Registrant's Annual Report on Form 10-K for the fiscal year ended
    February 28, 1998 (which incorporates by reference certain information from
    the Registrant's Proxy Statement relating to the 1998 Annual Meeting of
    Shareholders) (File No. 1-10288).

(b) The Registrant's Quarterly Report on Form 10-Q for the quarter ended May 31,
    1998 (File No. 1-10288).

(c) The Registrant's Current Report on Form 8-K filed on July 31, 1998 (File 
    No. 1-10288).

(d) The Registrant's Current Report on Form 8-K filed on March 31, 1998 (File
    No. 1-10288).

(e) The Registrant's Current Report on Form 8-K/A filed on March 4, 1998 (File
    No. 1-10288).

(f) All other reports filed by the Registrant with the Securities and Exchange
    Commission pursuant to Section 13(a) or Section 15(d) of the Securities
    Exchange Act of 1934 (the "Exchange Act") since the end of the fiscal year
    covered by the Registrant's Annual Report referred to above.

(g) The description of the common stock of the Registrant contained in the
    Registrant's Registration Statement on Form 8-A (File No. 1-10288) filed on
    April 9, 1989, including all amendments and reports filed for the purpose of
    updating such description.

     All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act prior to the filing of a post-
effective amendment which indicates that all securities offered have been sold
or which deregisters all securities then remaining unsold shall be deemed to be
incorporated by reference herein and to be a part hereof from the date of the
filing of such documents.

ITEM 4.  DESCRIPTION OF SECURITIES.

Not required.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

No material interests.

                                      -2-
<PAGE>
 
ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 145 of the Delaware General Corporation Law, as amended, provides
that a corporation may indemnify any person who was or is a party or is
threatened to be made a party to any threatened, pending or completed action,
suit or proceeding, whether civil, criminal or investigative (other than an
action by or in the right of the corporation) by reason of the fact that he is
or was a director, officer, employee or agent of the corporation, or is or was
serving at the request of the corporation as a director, officer, employee or
agent of another corporation, partnership, joint venture, trust or other
enterprise, against expenses (including attorneys' fees), judgments, fines and
amounts paid in settlement actually and reasonably incurred by him in connection
with such action, suit or proceeding if he acted in good faith and in a manner
he reasonably believed to be in or not opposed to the best interests of the
corporation, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful. Section 145 further
provides that a corporation similarly may indemnify any such person serving in
any such capacity who was or is a party or is threatened to be made a party to
any threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor, against expenses actually and
reasonably incurred in connection with the defense or settlement of such action
or suit if he acted in good faith and in a manner he reasonably believed to be
in or not opposed to the best interests of the corporation and except that no
indemnification shall be made in respect of any claim, issue or matter as to
which such person shall have been adjudged to be liable to the corporation
unless and only to the extent that the Delaware Court of Chancery or such other
court in which such action or suit was brought shall determine upon application
that, despite the adjudication of liability but in view of all the circumstances
of the case, such person is fairly and reasonably entitled to indemnity for such
expenses which the Court of Chancery or such other court shall deem proper.

        Section 102(b)(7) of the Delaware General Corporation Law, as amended,
permits a corporation to include in its certificate of incorporation a provision
eliminating or limiting the personal liability of a director to the corporation
or its stockholders for monetary damages for breach of fiduciary duty as a
director, provided that such provision shall not eliminate or limit the
liability of a director (i) for any breach of the director's duty of loyalty to
the corporation or its stockholders, (ii) for acts or omissions not in good
faith or which involve intentional misconduct or a knowing violation of law,
(ii) for acts or omissions not in good faith or which involve intentional
misconduct or a knowing violation of law, (iii) under Section 174 of the
Delaware General Corporation Law (relating to unlawful payment of dividends and
unlawful stock purchase and redemption), or (iv) for any transaction from which
the director derived an improper personal benefit.

        The Registrant's Restated Certificate of Incorporation, as amended,
provides that the Company's Directors shall not be liable to the Registrant or
its stockholders for monetary damages for breach of fiduciary duty as a
director, except to the extent that exculpation from liabilities is not
permitted under the Delaware General Corporation Law as in effect at the time
such liability is determined.  The Restated Certificate of Incorporation, as
amended, further provides that the Registrant shall indemnify its directors and
officers to the full extent permitted by the law of the State of Delaware.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

Not applicable.

                                      -3-
<PAGE>
 
ITEM 8.  EXHIBITS.

 4.1.  Specimen stock certificate representing Cabletron Common Stock
       which is incorporated by reference to Exhibit 4.1 of Cabletron's
       Registration Statement on Form S-1 (File No. 33-28055).

 5.1.  Opinion of Ropes & Gray.

23.1.  Consent of KMPG Peat Marwick LLP.
 
23.2.  Consent of Ropes & Gray (contained in the opinion filed as Exhibit
       5.1 to this registration statement).

23.3.  Consent of PricewaterhouseCoopers LLP.
 
24.1.  Power of Attorney (included in Part II of this registration statement
       under the caption "Signatures").

99.1.  FlowPoint Corp. 1994 Stock Option Plan.
 
99.2.  Form of Stock Option Agreement used in connection with the
       FlowPoint Corp. 1994 Stock Option Plan for Incentive Stock
       Options.
 
99.3.  Form of Stock Option Agreement used in connection with the
       FlowPoint Corp. 1994 Stock Option Plan for Nonstatutory Stock
       Options.
 
99.4.  Form of Stock Option Assumption Agreement used in connection
       with the FlowPoint Corp. 1994 Stock Option Plan.
 

ITEM 9.   UNDERTAKINGS.

     (a)  The undersigned Registrant hereby undertakes:

     (1) To file, during any period in which offers or sales are being made, a
post-effective amendment to this registration statement:

         (i) To include any prospectus required by Section 10(a)(3) of the
Securities Act;

         (ii) To reflect in the prospectus any facts or events arising after the
effective date of the registration statement (or the most recent post-effective
amendment thereof) which, individually or in the aggregate, represent a
fundamental change in the information set forth in the registration statement;

         (iii) To include any material information with respect to the plan of
distribution not previously disclosed in the registration statement or any
material change to such information in this registration statement;

                                      -4-
<PAGE>
 
     provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) above shall not
apply if the information required to be included in a post-effective amendment
by those paragraphs is contained in periodic reports filed by the Registrant
pursuant to Section 13 or Section 15(d) of the Exchange Act that are
incorporated by reference in the registration statement.

     (2)  That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

     (3)  To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering.

     (b)  The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

     (c)  Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable.  In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer, or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                      -5-
<PAGE>
 
                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Rochester, State of New Hampshire on this 15th
day of September, 1998.



                                  By:  /s/  David J. Kirkpatrick
                                      --------------------------------------  
                                      David J. Kirkpatrick
                                      Corporate Executive Vice President,
                                      Chief Financial Officer and Director


      Each person whose signature appears below constitutes and appoints Craig
R. Benson and David J. Kirkpatrick, and each of them individually, his true and
lawful attorney-in-fact and agent with full power of substitution and
resubstitution, for him and in his name, place and stead, in any and all
capacities, to sign any and all amendments (including post-effective amendments)
to this registration statement on Form S-8 to be filed by Cabletron Systems,
Inc., and to file the same, with all exhibits thereto, and other documents in
connection therewith, with the Securities and Exchange Commission, granting unto
said attorneys-in-fact and agents full power and authority to be done in and
about the premises, as fully to all intents and purposes as he might or could do
in person, hereby ratifying and confirming all that said attorneys-in-fact and
agents, or their substitutes, may lawfully do or cause to be done by virtue
hereof.

        Pursuant to the requirements of the Securities Act of 1933, this
registration statement on Form  S-8 has been signed below by the following
persons in the capacities shown on the date indicated.
 
Signatures                          Title                          Date
----------                          -----                          ----
 
/s/ Craig R. Benson          Chairman, President, Chief     September 15, 1998
---------------------------  Executive Officer,  
Craig R. Benson              Treasurer and Director
                             (principal executive officer)
 
/s/ David J. Kirkpatrick     Corporate Executive Vice       September 15, 1998
---------------------------  President, Chief Financial  
David J. Kirkpatrick         Officer and Director 
                             (principal financial and
                             accounting officer) 
 
/s/  Michael D. Myerow       Secretary and Director         September 15, 1998
---------------------------
Michael D. Myerow
 
/s/  Donald F. McGuinness    Director                       September 15, 1998
---------------------------
Donald F. McGuinness

                                      -6-
<PAGE>
 
                                 EXHIBIT INDEX


Exhibit                                                               Page
Number    Title of Exhibit                                           Number
-------   ----------------                                           ------

   4.1.  Specimen stock certificate representing Cabletron Common 
         Stock which is incorporated by reference to Exhibit 4.1 
         of Cabletron's Registration Statement on Form S-1 
         (File No. 33-28055).
 
   5.1.  Opinion of Ropes & Gray.
 
  23.1.  Consent of KMPG Peat Marwick LLP.
 
  23.2.  Consent of Ropes & Gray (contained in the opinion filed as 
         Exhibit 5.1 to this registration statement).

  23.3.  Consent of PricewaterhouseCoopers LLP.
 
  24.1.  Power of Attorney (included in Part II of this registration 
         statement under the caption "Signatures").

  99.1.  FlowPoint Corp. 1994 Stock Option Plan.

  99.2.  Form of Stock Option Agreement used in connection with the 
         FlowPoint Corp. 1994 Stock Option Plan for Incentive 
         Stock Options.
 
  99.3.  Form of Stock Option Agreement used in connection with the 
         FlowPoint 1994 Stock Option Plan for Nonstatutory 
         Stock Options.
 
  99.4.  Form of Stock Option Assumption Agreement used in connection 
         with the 1994 Stock Option Plan.