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                                                                     EXHIBIT 3.4

                            CERTIFICATE OF AMENDMENT
                         OF SECOND AMENDED AND RESTATED
                          CERTIFICATE OF INCORPORATION
                         OF COSINE COMMUNICATIONS, INC.

        CoSine Communications, Inc. (the "Corporation"), a corporation organized
and existing under and by virtue of the General Corporation Law of the State of
Delaware, does hereby certify:

        FIRST: The name of the Corporation is CoSine Communications, Inc.

        SECOND: The Corporation's original Certificate of Incorporation was
        filed with the Secretary of State of the State of Delaware on May 16,
        2000, a First Amended and Restated Certificate of Incorporation was
        filed with the Secretary of State of the State of Delaware on August 17,
        2000, and a Second Amended and Restated Certificate of Incorporation was
        filed with the Secretary of State of the State of Delaware on September
        29,2000.

        THIRD: The Board of Directors of the Corporation, acting in accordance
        with the provision of Sections 141 and 242 of the General Corporation
        Law of the State of Delaware adopted resolutions to amend the first
        paragraph of Article IV of the Second Amended and Restated Certificate
        of Incorporation of the Corporation to read in its entirety as follows:

                " The total number of shares of all classes of stock which the
        Corporation shall have authority to issue is 303,000,000, of which (i)
        300,000,000 shares, par value $0.0001 per share, are to be of a class
        designated Common Stock ("Common Stock") and (ii) 3,000,000 shares, par
        value $0.0001 per share, are to be of a class designated Preferred Stock
        ("Preferred Stock"). Effective as of 5:00 p.m., Eastern time, on the
        date this Certificate of Amendment of Amended and Restated Certificate
        of Incorporation is filed with the Secretary of State of the State of
        Delaware, each ten (10) shares of the Corporation's Common Stock, par
        value $.0001 per share, issued and outstanding shall, automatically and
        without any action on the part of the respective holders thereof, be
        combined and converted into one (1) share of Common Stock, par value
        $.0001 per share, of the Corporation; provided however, that the
        Corporation shall issue no fractional shares of Common Stock, but shall
        instead pay to any stockholder who would be entitled to receive a
        fractional share as a result of the actions set forth herein a sum in
        cash equal to such fraction multiplied by the average of the high and
        low prices of the Corporation's Common Stock as reported on the Nasdaq
        National Market for the five trading-day period ending on the last
        business day before the date this Certificate of Amendment of Amended
        and Restated Certificate of Incorporation is filed with the Secretary of
        State of the State of Delaware.

                The Preferred Stock may be issued from time to time in one or
        more series. The Board of Directors is hereby authorized, subject to any
        limitations prescribed by law, to fix by resolution or resolutions the
        designations, powers, preferences and rights, and the qualifications,
        limitations or restrictions thereof, of each such series of Preferred
        Stock, including without limitation authority to fix by resolution or
        resolutions, the dividend rights, dividend rate, conversion rights,
        voting rights, rights and terms of redemption (including sinking fund
        provisions), redemption price or prices, and liquidation preferences of
        any wholly unissued series of Preferred Stock, and the number of shares
        constituting any such series and the designation thereof, or any of the
        foregoing.

                The Board of Directors is further authorized to increase (but
        not above the total number of authorized shares of the class) or
        decrease (but not below the number of shares of any such series then
        outstanding) the number of shares of any series, the number of which was
        fixed by it, subsequent to the issue of shares of such series then
        outstanding, subject to the powers, preferences and rights, and the
        qualifications, limitations and restrictions thereof stated in the
        resolution of the Board of Directors originally fixing the number of
        shares of such series. If the number of shares of any series is so
        decreased, then the shares constituting such decrease shall resume the
        status which they had prior to the adoption of the resolution originally
        fixing the number of shares of such series."

        FOURTH: This Certificate of Amendment of Second Amended and Restated
        Certificate of Incorporation was submitted to the stockholders of the
        Corporation and was duly approved by the required vote of stockholders
        of the Corporation in accordance with Sections 222 and 242 of the
        Delaware General Corporation Law. The total number of outstanding shares
        entitled to vote or consent to this Amendment was 102,505,521 shares of
        Common Stock. A




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        majority of the outstanding shares of Common Stock, voting together as a
        single class, voted in favor of this Certificate of Amendment of Second
        Amended and Restated Certificate of Incorporation. The vote required was
        a majority of the outstanding shares of Common Stock, voting together as
        a single class.

        IN WITNESS WHEREOF, CoSine Communications, Inc. has caused this
        Certificate of Amendment to be signed by its Chief Executive Officer as
        of September 17, 2002.


                                        COSINE COMMUNICATIONS, INC.


                                        /s/ Stephen Goggiano
                                        ----------------------------------------
                                        Stephen Goggiano
                                        Chief Executive Officer