<PAGE>

                                                                   EXHIBIT 3.1

                              AMENDED AND RESTATED
                          CERTIFICATE OF INCORPORATION

                                       OF

                                INTERSPEED, INC.

      INTERSPEED, INC., a corporation organized and existing under the laws
of the State of Delaware (the "Corporation"), hereby certifies as follows:

         1. The name of the Corporation is Interspeed, Inc. The date of the
filing of its original Certificate of Incorporation (the "Original Certificate")
with the Secretary of State of the State of Delaware was June 16, 1999.

         2. This Amended and Restated Certificate of Incorporation amends,
restates and integrates the provisions of the Original Certificate and (i) was
duly adopted by the Board of Directors in accordance with the provisions of
Section 245 of the Delaware General Corporation Law (the "DGCL"), (ii) was
declared by the Board of Directors to be advisable and in the best interests of
the Corporation and was directed by the Board of Directors to be submitted to
and be considered by the stockholders of the Corporation entitled to vote
thereon for approval by the affirmative vote of such stockholders in accordance
with Section 242 of the DGCL and (iii) was duly adopted by a consent in lieu of
a meeting of the holders of the Corporation's common stock, par value $.01 per
share (the "Common Stock"), in accordance with the provisions of Sections 228
and 242 of the DGCL, such holders being all of the holders of the Corporation's
capital stock entitled to vote thereon.

         3. The text of the Original Certificate is hereby amended and restated
in its entirety to provide as herein set forth in full.

                                    ARTICLE I

                                      NAME
                                      ----

         The name of the Corporation is Interspeed, Inc.

                                   ARTICLE II

                                REGISTERED OFFICE
                                -----------------

         The address of the registered office of the Corporation in the State of
Delaware is c/o The Corporation Trust Company, 1209 Orange Street, in the City
of Wilmington, County of


<PAGE>

New Castle.  The name of its registered agent at such address is The Corporation
Trust Company.

                                   ARTICLE III

                                    PURPOSES
                                    --------

        The purpose of the Corporation is to engage in any lawful act or
activity for which corporations may be organized under the DGCL.

                                   ARTICLE IV

                                  CAPITAL STOCK
                                  -------------

         SECTION 1. NUMBER OF SHARES.

         The total number of shares of capital stock which the Corporation shall
have the authority to issue is 31,000,000 shares, of which 30,000,000 shares
shall be Common Stock, par value $.01 per share (the "Common Stock") and (ii)
1,000,000 shares shall be Undesignated Preferred Stock, par value $.01 per share
(the "Undesignated Preferred Stock").

         As set forth in this Article IV, the Board of Directors or any
authorized committee thereof is authorized from time to time to establish and
designate one or more series of Undesignated Preferred Stock, to fix and
determine the variations in the relative rights and preferences as between the
different series of Undesignated Preferred Stock in the manner hereinafter set
forth in this Article IV, and to fix or alter the number of shares comprising
any such series and the designation thereof to the extent permitted by law.

         The number of authorized shares of the class of Undesignated Preferred
Stock may be increased or decreased (but not below the number of shares
outstanding) by the affirmative vote of the holders of a majority of the Common
Stock, without a vote of the holders of the Undesignated Preferred Stock,
pursuant to the resolution or resolutions establishing the class of Undesignated
Preferred Stock or this Amended and Restated Certificate of Incorporation, as it
may be amended from time to time.

         SECTION 2. GENERAL.

         The designations, powers, preferences and rights of, and the
qualifications, limitations and restrictions upon, each class or series of stock
shall be determined in accordance with, or


                                        2

<PAGE>

as set forth below in, Sections 3 and 4 of this Article IV.

         SECTION 3. COMMON STOCK.

         Subject to all of the rights, powers and preferences of the
Undesignated Preferred Stock, and except as provided by law or in this Article
IV (or in any certificate of designation of any series of Undesignated Preferred
Stock) or by the Board of Directors or any authorized committee thereof pursuant
to this Article IV:

                  (a) the holders of the Common Stock shall have the exclusive
right to vote for the election of Directors and on all other matters requiring
stockholder action, each share being entitled to one vote;

                  (b) dividends may be declared and paid or set apart for
payment upon the Common Stock out of any assets or funds of the Corporation
legally available for the payment of dividends, but only when and as declared by
the Board of Directors or any authorized committee thereof; and

                  (c) upon the voluntary or involuntary liquidation, dissolution
or winding up of the Corporation, the net assets of the Corporation shall be
distributed pro rata to the holders of the Common Stock.

         SECTION 4. UNDESIGNATED PREFERRED STOCK.

         Subject to any limitations prescribed by law, the Board of Directors or
any authorized committee thereof is expressly authorized to provide for the
issuance of the shares of Undesignated Preferred Stock in one or more series of
such stock, and by filing a certificate pursuant to applicable law of the State
of Delaware, to establish or change from time to time the number of shares to be
included in each such series, and to fix the designations, powers, preferences
and the relative, participating, optional or other special rights of the shares
of each series and any qualifications, limitations and restrictions thereof. Any
action by the Board of Directors or any authorized committee thereof under this
Article IV.4 shall require the affirmative vote of a majority of the Directors
then in office or a majority of the members of such committee. The Board of
Directors or any authorized committee thereof shall have the right to determine
or fix one or more of the following with respect to each series of Undesignated
Preferred Stock to the extent permitted by law:

                  (a) The distinctive serial designation and the number of
shares constituting such series;

                  (b) The dividend rates or the amount of dividends to be paid
on the shares of such series, whether dividends shall be cumulative and, if so,
from which date or dates, the payment date or dates for dividends, and the
participating and other rights, if any, with respect


                                        3

<PAGE>

to dividends;

                  (c) The voting rights and powers, full or limited, if any, of
the shares of such series;

                  (d) Whether the shares of such series shall be redeemable and,
if so, the price or prices at which, and the terms and conditions on which, such
shares may be redeemed;

                  (e) The amount or amounts payable upon the shares of such
series and any preferences applicable thereto in the event of voluntary or
involuntary liquidation, dissolution or winding up of the Corporation;

                  (f) Whether the shares of such series shall be entitled to the
benefit of a sinking or retirement fund to be applied to the purchase or
redemption of such shares, and if so entitled, the amount of such fund and the
manner of its application, including the price or prices at which such shares
may be redeemed or purchased through the application of such fund;

                  (g) Whether the shares of such series shall be convertible
into, or exchangeable for, shares of any other class or classes or of any other
series of the same or any other class or classes of stock of the Corporation
and, if so convertible or exchangeable, the conversion price or prices, or the
rate or rates of exchange, and the adjustments thereof, if any, at which such
conversion or exchange may be made, and any other terms and conditions of such
conversion or exchange;

                  (h) The price or other consideration for which the shares of
such series shall be issued;

                  (i) Whether the shares of such series which are redeemed or
converted shall have the status of authorized but unissued shares of
Undesignated Preferred Stock (or series thereof) and whether such shares may be
reissued as shares of the same or any other class or series of stock; and

                  (j) Such other powers, preferences, rights, qualifications,
limitations and restrictions thereof as the Board of Directors or any authorized
committee thereof may deem advisable.

                                    ARTICLE V

                               STOCKHOLDER ACTION
                               ------------------

         SECTION 1.  ACTION WITHOUT MEETING.


                                       4

<PAGE>

         Except as otherwise provided herein, any action required or permitted
to be taken by the stockholders of the Corporation at any annual or special
meeting of stockholders of the Corporation must be effected at a duly called
annual or special meeting of stockholders and may not be taken or effected by a
written consent of stockholders in lieu thereof.

         SECTION 2. SPECIAL MEETINGS.

         Except as otherwise required by law and subject to the rights, if any,
of the holders of any series of Undesignated Preferred Stock, special meetings
of the stockholders of the Corporation may be called only by the Board of
Directors pursuant to a resolution approved by the majority of the Directors
then in office.

                                   ARTICLE VI

                                    DIRECTORS
                                    ---------

         SECTION 1.  GENERAL.

         The business and affairs of the Corporation shall be managed by or
under the direction of the Board of Directors except as otherwise provided
herein or required by law.

         SECTION 2.  ELECTION OF DIRECTORS.

         Election of Directors need not be by written ballot unless the By-laws
of the Corporation shall so provide.

         SECTION 3.  TERMS OF DIRECTORS.

         The number of Directors of the Corporation shall be fixed by resolution
duly adopted from time to time by the Board of Directors. The Directors, other
than those who may be elected by the holders of any series of Undesignated
Preferred Stock of the Corporation, shall be classified, with respect to the
term for which they severally hold office, into three classes, as nearly equal
in number as possible. The initial Class I Directors of the Corporation shall be
Eric R. Giler and Rajeev Agarwal; the initial Class II Directors of the
Corporation shall be Stephen A. Ide and Robert G. Barrett; and the initial Class
III Director of the Corporation shall be Paul J. Severino. The initial Class I
Directors shall serve for a term expiring at the annual meeting of stockholders
to be held in 2000, the initial Class II Directors shall serve for a term
expiring at the annual meeting of stockholders to be held in 2001, and the
initial Class III Director shall serve for a term expiring at the annual meeting
of stockholders to be held in 2002. At each annual meeting of stockholders, the
successor or successors of the class of Directors whose term expires at that
meeting shall be elected by a plurality of the votes cast at such meeting and
shall hold office for a term expiring at the annual meeting of stockholders


                                        5

<PAGE>

held in the third year following the year of their election. The Directors
elected to each class shall hold office until their successors are duly elected
and qualified or until their earlier resignation or removal.

         Notwithstanding the foregoing, whenever, pursuant to the provisions of
Article IV of this Amended and Restated Certificate of Incorporation, the
holders of any one or more series of Undesignated Preferred Stock shall have the
right, voting separately as a series or together with holders of other such
series, to elect Directors at an annual or special meeting of stockholders, the
election, term of office, filling of vacancies and other features of such
directorships shall be governed by the terms of this Amended and Restated
Certificate of Incorporation and any certificate of designations applicable
thereto, and such Directors so elected shall not be divided into classes
pursuant to this Article VI.3.

         SECTION 4. VACANCIES.

         Subject to the rights, if any, of the holders of any series of
Undesignated Preferred Stock to elect Directors and to fill vacancies in the
Board of Directors relating thereto, any and all vacancies in the Board of
Directors, however occurring, including, without limitation, by reason of an
increase in size of the Board of Directors, or the death, resignation,
disqualification or removal of a Director, shall be filled solely by the
affirmative vote of a majority of the remaining Directors then in office, even
if less than a quorum of the Board of Directors. Any Director appointed in
accordance with the preceding sentence shall hold office for the remainder of
the full term of the class of Directors in which the new directorship was
created or the vacancy occurred and until such Director's successor shall have
been duly elected and qualified or until his or her earlier resignation or
removal. Subject to the rights, if any, of the holders of any series of
Undesignated Preferred Stock to elect Directors, when the number of Directors is
increased or decreased, the Board of Directors shall determine the class or
classes to which the increased or decreased number of Directors shall be
apportioned; provided, however, that no decrease in the number of Directors
shall shorten the term of any incumbent Director. In the event of a vacancy in
the Board of Directors, the remaining Directors, except as otherwise provided by
law, may exercise the powers of the full Board of Directors until the vacancy is
filled.

         SECTION 5. REMOVAL.

         Subject to the rights, if any, of any series of Undesignated Preferred
Stock to elect Directors and to remove any Director whom the holders of any such
stock have the right to elect, any Director (including persons elected by
Directors to fill vacancies in the Board of Directors) may be removed from
office (i) only with cause and (ii) only by the affirmative vote of the holders
of two-thirds of the shares then entitled to vote at an election of Directors.
At least 30 days prior to any meeting of stockholders at which it is proposed
that any Director be removed from office, written notice of such proposed
removal shall be sent to the Director whose removal will be considered at the
meeting.


                                        6

<PAGE>

                                   ARTICLE VII

                             LIMITATION OF LIABILITY
                             -----------------------

         A Director of the Corporation shall not be personally liable to the
Corporation or its stockholders for monetary damages for breach of fiduciary
duty as a Director, except for liability (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, (iii) under Section 174 of the DGCL or (iv) for any
transaction from which the Director derived an improper personal benefit. If the
DGCL is amended after the effective date of this Amended and Restated
Certificate of Incorporation to authorize corporate action further eliminating
or limiting the personal liability of Directors, then the liability of a
Director of the Corporation shall be eliminated or limited to the fullest extent
permitted by the DGCL, as so amended.

         Any repeal or modification of this Article VII by either of (i) the
stockholders of the Corporation or (ii) an amendment to the DGCL, shall not
adversely affect any right or protection existing at the time of such repeal or
modification with respect to any acts or omissions occurring before such repeal
or modification of a person serving as a Director at the time of such repeal or
modification.

                                  ARTICLE VIII

                              AMENDMENT OF BY-LAWS
                              --------------------

         SECTION 1. AMENDMENT BY DIRECTORS

         Except as otherwise provided by law, the By-laws of the Corporation may
be amended or repealed by the Board of Directors by the affirmative vote of a
majority of the Directors then in office.

         SECTION 2. AMENDMENT BY STOCKHOLDERS

         The By-laws of the Corporation may be amended or repealed at any annual
meeting of stockholders, or special meeting of stockholders called for such
purpose as provided in the Bylaws, by the affirmative vote of at least
two-thirds of the shares present in person or represented by proxy at such
meeting and entitled to vote on such amendment or repeal, voting together as a
single class; provided, however, that if the Board of Directors recommends that
stockholders approve such amendment or repeal at such meeting of stockholders,
such amendment or repeal shall only require the affirmative vote of the majority
of the shares present in person or represented by proxy at such meeting and
entitled to vote on such amendment or repeal by holders of voting stock, voting
together as a single class.


                                        7

<PAGE>

                                   ARTICLE IX

                    AMENDMENT OF CERTIFICATE OF INCORPORATION
                    -----------------------------------------

         The Corporation reserves the right to amend or repeal this Amended and
Restated Certificate of Incorporation in the manner now or hereafter prescribed
by statute and this Amended and Restated Certificate of Incorporation, and all
rights conferred upon stockholders herein are granted subject to this
reservation. No amendment or repeal of this Amended and Restated Certificate of
Incorporation shall be made unless the same is first approved by the Board of
Directors pursuant to a resolution adopted by the Board of Directors in
accordance with Section 242 of the DGCL, and, except as otherwise provided by
law, thereafter approved by the stockholders. Whenever any vote of the holders
of voting stock is required, and in addition to any other vote of holders of
voting stock that is required by this Amended and Certificate of Incorporation
or by law, the affirmative vote of the majority of the outstanding shares
entitled to vote on such amendment or repeal, and the affirmative vote of the
majority of the outstanding shares of each class entitled to vote thereon as a
class, at a duly constituted meeting of stockholders called expressly for such
purpose shall be required to amend or repeal any provisions of this Amended and
Restated Certificate of Incorporation; provided, however, that the affirmative
vote of not less than two-thirds of the outstanding shares entitled to vote on
such amendment or repeal, and the affirmative vote of not less than two-thirds
of the outstanding shares of each class entitled to vote thereon as a class,
shall be required to amend or repeal any of the provisions of Article V, VI, VII
or Article IX of this Amended and Restated Certificate of Incorporation.


                                        8

<PAGE>

         This Amended and Restated Certificate of Incorporation is executed as
of this 23rd day of September, 1999.

                                            INTERSPEED, INC.

                                            By: /s/ Stephen A. Ide
                                               --------------------------------
                                               Stephen A. Ide, President