1
 
                         PENRIL DATACOMM NETWORKS, INC.
 
               SPECIAL MEETING OF SHAREHOLDERS, NOVEMBER 15, 1996
          THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS
 
    The undersigned hereby appoints Richard D. Rose or C. P. Houston as proxy,
each with power to appoint his substitute, and hereby authorizes each of them to
vote as directed below all the shares of common stock, $.01 par value, of Penril
DataComm Networks, Inc. ("Penril") which the undersigned would be entitled to
vote, if personally present, at the Special Meeting of Shareholders of Penril to
be held at 1201 Quince Orchard Blvd., Gaithersburg, Maryland, on November 15,
1996 at 9 o'clock A.M. (local time), or any postponement or adjournments
thereof.
 
SINGLE PROPOSAL TO
 
1. APPROVE THE TRANSFER AND CONTRIBUTION of Penril's and each of its
   subsidiaries (other than Penril International, Ltd., a United States Virgin
   Islands corporation, and Penril DataComm Ltd., a United Kingdom corporation)
   remote access products business and substantially all of their other
   businesses, assets and liabilities unrelated to Penril's modem business to
   Access Beyond, Inc. ("Access Beyond"), a Delaware corporation and
   wholly-owned subsidiary of Penril, and the distribution and transfer to
   shareholders of Penril all of the outstanding capital stock of Access Beyond
   (the "Spin-off Transaction"); and
 
2. APPROVE AND ADOPT THE PLAN AND AGREEMENT OF MERGER dated as of June 16, 1996,
   as amended on August 5, 1996 (the "Merger Agreement"), between Penril, Bay
   Networks, Inc. ("Bay"), a Delaware corporation; and Beta Acquisition Corp., a
   Delaware corporation and wholly-owned subsidiary of Bay ("Merger Sub"), and
   the Merger of Merger Sub with and into Penril upon the terms and subject to
   the conditions thereof (the "Merger"), pursuant to which Penril will become a
   wholly-owned subsidiary of Bay and shares of common stock of Penril will be
   converted into the right to receive the number of shares of common stock,
   $.01 par value, of Bay ("Bay Common Stock"), as is equal to the Conversion
   Ratio, determined by dividing $10.00 by the average closing price for Bay
   Common Stock on the New York Stock Exchange for a specified period prior to
   closing, on the terms and subject to the conditions set forth in the Merger
   Agreement. Options to purchase common stock of Penril will be assumed by Bay
   and converted into options to acquire shares of Bay Common Stock on the terms
   and subject to the conditions set forth in the Merger Agreement and in the
   award agreements pursuant to which such options were awarded.
 
                      (Continued, and to be dated and signed, on the other side)
 
(Continued from the other side)
 
    The proposal to approve the Spin-off Transaction and the Merger will be
voted upon as a single proposal.
 
            FOR / /               AGAINST / /               ABSTAIN / /
 
    This Proxy, when properly executed, will be voted in the manner directed
above. IF NO DIRECTION IS MADE, THIS PROXY WILL BE VOTED FOR THE PROPOSAL TO
APPROVE THE SPIN-OFF TRANSACTION, THE MERGER AGREEMENT AND THE MERGER.
 
    The undersigned acknowledges receipt from Penril prior to the execution of
this Proxy of the Proxy Statement dated October     , 1996.
 
                                                   Please sign exactly as name
                                                   appears below.
 
                                                   Date:                  , 1996
 
                                                   -----------------------------
                                                             Signature
 
                                                   When shares are held by joint
                                                   tenants, either may sign.
                                                   When signing as attorney,
                                                   executor, administrator,
                                                   trustee or guardian, please
                                                   give full title as such. If a
                                                   corporation, please sign in
                                                   full corporate name by the
                                                   President or other authorized
                                                   officer. If a partnership,
                                                   please sign in partnership
                                                   name by an authorized person.
 
                                                   PLEASE SIGN, DATE AND RETURN
                                                   THIS PROXY PROMPTLY USING THE
                                                        ENCLOSED ENVELOPE.
 
                                                   / / If you plan to attend the
                                                   Special Meeting, please check
                                                   this box.
 
                                   Proxy Card