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EXHIBIT 5.1
                   SOKOLOW, DUNAUD, MERCADIER & CARRERAS, LLP
                              50 Rockefeller Plaza
                                    Suite 928
                               New York, NY 10020
                                 (212) 315-0175


                                 October 6, 1999

FastComm Communications Corporation
45472 Holiday Drive
Sterling, VA 20166

Ladies and Gentlemen:

     We have acted as counsel to FastComm Communications Corporation, a Virginia
corporation (the "Company"), in connection with the registration statement on
Form S-3 (No. 333-85665) (the "Registration Statement") pertaining to the
proposed offering of 3,080,399 shares of common stock, $.01 par value per share
(the "Shares"), as described in the Registration Statement. The Shares were
issued in connection with the acquisition of KG Data Systems, Inc. and in a
private placement to certain accredited investors and are issuable upon the
exercise of certain warrants described in the Registration Statement (the
"Warrants"). As such counsel, you have requested our opinion as to the matters
described herein relating to the Shares. All capitalized terms used but not
defined herein shall have the meanings assigned to them in the Registration
Statement.

     We have examined the Company's certificate of incorporation and by-laws, in
each case as amended or restated through the date hereof; the agreements related
to each of the Warrants (the "Warrant Agreements"); minutes of the Company's
corporate proceedings throughout the date hereof, as made available to us by
officers of the Company; an executed copy of the Registration Statement and all
exhibits thereto in the form filed with the Securities and Exchange Commission;
and such matters of law and such documents and other instruments as we have
deemed necessary by us in order to deliver the within opinion. In the course of
our examination, we have assumed the genuineness of all signatures, the
authority of all signatories to sign on behalf of their principals, if any, the
authenticity of all documents submitted to us as original documents and the
conformity to original documents of all documents submitted to us as certified
or photostatic copies. As to certain factual matters, we have relied upon
information furnished to us by officers of the Company.

     Based on the foregoing and solely in reliance thereon, it is our opinion
that the Shares have been duly authorized, and when they are issued upon
exercise of the Warrants, against payment of the consideration therefore
contemplated by the Warrant Agreements, as the case may be, the Shares will be
validly issued, fully paid and non-assessable.

     We hereby consent to the filing of this letter as an exhibit to the
Registration Statement and to the reference to it in the prospectus included
therein under the caption "Legal Matters." In giving such consent, we do not
admit that we are in the category of persons whose consent is required under
Section 7 of the Act.

                                           Very truly yours,

                                           SOKOLOW, DUNAUD, MERCADIER & CARRERAS


                                           By: /s/ Thomas G. Amon
                                                A member of the Firm