FIRST SUPPLEMENTAL INDENTURE

        THIS FIRST SUPPLEMENTAL INDENTURE dated as of June 1, 2005 (this "Supplemental Indenture"), is entered into by and among McDATA Corporation, a Delaware corporation ("McDATA"), Computer Network Technology Corporation, a Minnesota corporation (the "Company"), and U.S. Bank National Association, a national banking association, as trustee (the "Trustee"). Capitalized terms used herein and not otherwise defined have the meanings set forth in the Indenture referred to below.

RECITALS

        A.    The Company has heretofore executed and delivered to the Trustee an indenture dated as of February 20, 2002 (the "Indenture"), providing for the issuance of 3.00% Convertible Subordinated Notes due 2007 of the Company (the "Securities").

        B.    The Company has entered into an Agreement and Plan of Merger dated as of January 17, 2005, by and among McDATA, Condor Acquisition, Inc., a Minnesota corporation and a wholly-owned subsidiary of McDATA ("Merger Sub"), and the Company (the "Merger Agreement"), providing for the merger of Merger Sub with and into the Company with the Company as the surviving corporation and a wholly-owned subsidiary of McDATA (the "Merger").

        C.    Pursuant to Section 2.02(a) of the Merger Agreement, at the effective time of the Merger, each outstanding share of the Company's Common Stock, $0.01 par value per share ("Company Stock"), shall be converted into the right to receive 1.3 shares of McDATA's Class A Common Stock, $0.01 par value per share ("McDATA Stock") together with cash in lieu of fractional shares).

        D.    Pursuant to Section 4.11 of the Indenture, as a condition precedent to any merger effecting a change in the kind and amount of shares and other property issuable upon the conversion of the Securities, the Company and McDATA shall execute and deliver to the Trustee a supplemental indenture providing that the Holder of each Security then outstanding shall have the right to convert such Security into such other securities and property receivable in the merger by a holder of Company Stock.

        E.    In accordance with Section 11.1(a) of the Indenture the Company and the Trustee may amend or supplement the Indenture or the Securities to comply with Section 4.11 without notice to or consent of any Securityholder.

        F.     The Company and McDATA desire and have requested the Trustee to enter into this Supplemental Indenture for the purpose of amending the Indenture to provide that, upon conversion of the Securities under the Indenture, a Holder of Securities will receive McDATA Stock in lieu of Company Stock to which such Holder otherwise would have been entitled upon conversion.

        G.    McDATA has agreed to become a co-obligor with respect to the Securities by assuming the guaranty obligation set forth in Article Three of this Supplemental Indenture.

        H.    Each of the Company and McDATA has duly authorized the execution and delivery of this Supplemental Indenture.

        NOW, THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereto hereby covenant and agree for the equal and ratable benefit of the Holders of the Securities as follows:

ARTICLE ONE
RELATION TO INDENTURE; DEFINITIONS

        Section 1.01 Relation to Indenture. This Supplemental Indenture constitutes an integral part of the Indenture. In the event of inconsistencies between the Indenture and this Supplemental Indenture, the terms of this Supplemental Indenture shall govern.

        Section 1.02. Definitions. The definitions of "Board of Directors", "Common Stock", "Officer" and "Officers' Certificate" in Section 1.1 of the Indenture is hereby amended and restated in its entirety to read as follows:

        "Board of Directors" means the Board of Directors of the Company (or where so specified, of McDATA Corporation ("McDATA")) or any authorized committee of such Board of Directors.

        "Common Stock" means the Class A common stock of McDATA, par value $0.01 per share, as it exists on the date of the First Supplemental Indenture, and any shares of any class or classes of Capital Stock of McDATA resulting from any reclassification or reclassifications thereof and which have no preference in respect of dividends or of amounts payable in the event of any voluntary or involuntary liquidation, dissolution or winding-up of McDATA and which are not subject to redemption by McDATA; provided, however, that if at any time there shall be more than one such resulting class, the shares of each such class then so issuable on conversion of Securities shall be substantially in the proportion which the total number of shares of such class resulting from all such reclassifications bears to the total number of shares of all such classes resulting from all such reclassifications.

        "Officer" means the Chairman of the Board, the Chief Executive Officer, the President, any Vice President, the Chief Financial Officer, the Controller, the Secretary or any Assistant Secretary, the Treasurer or any Assistant Treasurer of the Company (or where so specified, of McDATA).

        "Officers' Certificate" means a certificate signed by two Officers; provided, however, that for purposes of Sections 4.11 and 6.3, "Officers' Certificate" means a certificate signed by the principal executive officer, principal financial officer or principal accounting officer of the Company (or where so specified, of McDATA) and by one other Officer.

ARTICLE TWO
AMENDMENTS

        Section 2.01 Conversion. Article IV of the Indenture is hereby amended and restated in its entirety to read as set forth on Annex A hereto.

        Section 2.02 Consolidation, Etc., on Certain Terms. Section 7.1 of the Indenture is hereby amended and restated to read as follows:

        Section 7.1 Company and McDATA May Consolidate, Etc., Only on Certain Terms

        Neither the Company nor McDATA shall consolidate with or merge into any other Person (in a transaction in which the Company or McDATA, as the case may be, is not the surviving

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corporation) or convey, transfer or lease its properties and assets substantially as an entirety to any Person, unless:

        (1)   in case the Company shall consolidate with or merge into another Person (in a transaction in which the Company is not the surviving corporation) or convey, transfer or lease its properties and assets substantially as an entirety to any Person, the Person formed by such consolidation or into which the Company is merged or the Person which acquires by conveyance or transfer, or which leases, the properties and assets of the Company substantially as an entirety shall be a corporation, limited liability company, partnership or trust, shall be organized and validly existing under the laws of the United States of America, any State thereof or the District of Columbia and shall expressly assume, by an indenture supplemental hereto, executed and delivered to the Trustee, in form satisfactory to the Trustee, the due and punctual payment of the principal of and any premium and interest on all the Securities and the performance or observance of every covenant of this Indenture on the part of the Company to be performed or observed and the conversion rights shall be provided for in accordance with Article IV, by supplemental indenture satisfactory in form to the Trustee, executed and delivered to the Trustee, by the Person (if other than the Company) formed by such consolidation or into which the Company shall have been merged or by the Person which shall have acquired the Company's assets;

        (2)   in case McDATA shall consolidate with or merge into another Person (in a transaction in which McDATA is not the surviving corporation) or convey, transfer or lease its properties and assets substantially as an entirety to any Person, the Person formed by such consolidation or into which McDATA is merged or the Person which acquires by conveyance or transfer, or which leases, the properties and assets of McDATA substantially as an entirety shall be a corporation, limited liability company, partnership or trust, shall be organized and validly existing under the laws of the United States of America, any State thereof or the District of Columbia and shall expressly assume, by an indenture supplemental hereto, executed and delivered to the Trustee, in form satisfactory to the Trustee, the obligations of McDATA under the guaranty set forth in Article Three of the First Supplemental Indenture dated as of June 1, 2005, and assume the performance or observance of every covenant of this Indenture on the part of McDATA to be performed or observed by it and the conversion rights shall be provided for in accordance with Article IV, by supplemental indenture satisfactory in form to the Trustee, executed and delivered to the Trustee, by the Person (if other than McDATA) formed by such consolidation or into which McDATA shall have been merged or by the Person which shall have acquired McDATA's assets;

        (3)   immediately after giving effect to such transaction in clause (1) or (2) of this Section 7.1, no Event of Default, and no event which, after notice or lapse of time or both, would become an Event of Default, shall have happened and be continuing; and

        (4)   the Company or McDATA, as the case may be, has delivered to the Trustee an Officers' Certificate and an Opinion of Counsel, each stating that such consolidation, merger, conveyance, transfer or lease and, if a supplemental indenture is required in connection with such transaction, such supplemental indenture comply with this Article VII and that all conditions precedent herein provided for relating to such transaction have been complied with.

        Section 2.03 Successor Substituted. Section 7.2 of the Indenture is hereby amended and restated in its entirety to read as follows:

        Upon any consolidation of the Company or McDATA with, or merger of the Company or McDATA into, any other Person or any conveyance, transfer or lease of the properties and assets of the Company or McDATA substantially as an entirety in accordance with Section 7.1, the successor Person formed by such consolidation or into which the Company or McDATA is merged or to which such conveyance, transfer or lease is made shall succeed to, and be substituted for, and may exercise every right and power of, the Company or McDATA, as the case may be, under this

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Indenture with the same effect as if such successor Person had been named as the Company or McDATA herein, and thereafter, except in the case of a lease, the predecessor Person shall be relieved of all obligations and covenants under this Indenture and the Securities."

        Section 2.04 Events of Default. Section 8.1 of the Indenture is hereby amended to add new clauses (6) and (7) to read as follows:

        (6)   McDATA pursuant to or within the meaning of any Bankruptcy Law:

        (i)    commences a voluntary case or proceeding;

        (ii)   consents to the entry of an order for relief against it in an involuntary case or proceeding;

        (iii)  consents to the appointment of a Custodian of it or for all or substantially all of its property; or

        (iv)  makes a general assignment for the benefit of its creditors; or

        (7)   a court of competent jurisdiction enters an order or decree under any Bankruptcy Law that:

        (i)    is for relief against McDATA in an involuntary case or proceeding;

        (ii)   appoints a Custodian of McDATA or for all or substantially all of the property of McDATA; or

        (iii)  orders the liquidation of McDATA;

        Section 2.05 No Recourse Against Others. Section 13.10 of the Indenture is hereby amended and restated in its entirety to read as follows:

        All liability described in paragraph 18 of the Securities of any director, officer, employee or shareholder, as such, of the Company or McDATA is waived and released.

        Section 2.06 Form of Security. Annex B of the Indenture is amended and restated in its entirety in the form attached to this Supplemental Indenture. Upon the execution of this Supplemental Indenture, the Company shall execute and the Trustee shall authenticate and deliver, Securities in the form set forth in Annex B, in substitution for, Securities then outstanding and all Securities presented or delivered to the Trustee on and after the date hereof shall be in the form of Annex B attached hereto to give effect to this Supplemental Indenture.

        The Trustee shall not at any time be under any responsibility to acquire or cause any Security now or hereafter outstanding to be presented or delivered to it for any purposes provided for in this Section 2.06.

ARTICLE THREE
MCDATA GUARANTY

        Section 3.01 McDATA Guaranty.

        (a)   Subject to the provisions of this Article Three, McDATA fully and unconditionally guarantees to each Holder of Securities hereunder and to the Trustee on behalf of the Holders: (1) the due and punctual payment of the principal of, premium, if any, and interest on each Security, when and as the same shall become due and payable, whether at maturity, by acceleration or otherwise, all in accordance with the terms of the Security and the Indenture and (2) in the case of any extension of time of payment or renewal of any Securities or any of such other obligations, that the same will be promptly paid in full when due in accordance with the terms of the extension or renewal, at the stated

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maturity, by acceleration or otherwise, subject, however, in the case of clauses (1) and (2) above, to the limitations set forth in the next succeeding paragraph (the "McDATA Guaranty").

        (b)   McDATA hereby waives diligence, presentment, demand of payment, filing of claims with a court in the event of merger or bankruptcy of the Company, any right to require a Holder to pursue any right or take any action (including, without limitation, a presentment, protest, demand for payment, notice of dishonor or any other notice) against the Company, the benefit of discussion, protest or notice with respect to any such Security or the debt evidenced thereby and all demands whatsoever (except as specified above), and covenants that the McDATA Guaranty will not be discharged as to any such Security except by payment in full of the principal thereof and interest thereon or as provided in Section 10.1 of the Indenture. In the event of any declaration of acceleration of such obligations as provided in Article 8 of the Indenture, such obligations (whether or not due and payable) shall forthwith become due and payable by McDATA for the purposes of this Article Three. In addition, without limiting the foregoing provisions, upon the effectiveness of an acceleration under Article 8 of the Indenture, the Trustee shall promptly make a demand for payment on the Securities under the McDATA Guaranty provided for in this Article Three.

        (c)   If the Trustee or any Holder is required by any court or otherwise to return to the Company or McDATA, or any custodian, receiver, liquidator, trustee, sequestrator or other similar official acting in relation to the Company or McDATA, any amount paid to the Trustee or such Holder in respect of a Security, the McDATA Guaranty, to the extent theretofore discharged, shall be reinstated in full force and effect. McDATA further agrees, to the fullest extent that it may lawfully do so, that, as between it, on the one hand, and the Holders and the Trustee, on the other hand, the maturity of the obligations guarantied hereby may be accelerated as provided in Article 8 of the Indenture for the purposes of the McDATA Guaranty, notwithstanding any stay, injunction or other prohibition extant under any applicable bankruptcy law preventing such acceleration in respect of the obligations guarantied hereby.

        (d)   McDATA shall be subrogated to the rights of the Holders of any Security against the Company but only to the extent and in the amount that a joint and several obligor with the Company would be entitled to contribution from the Company, in respect of any amount paid by McDATA to any Holder pursuant to the provisions of the McDATA Guaranty; provided, that McDATA shall not be entitled to enforce, or to receive any payments arising out of or based upon, such right of subrogation until the principal of, premium, if any, and interest on all the Securities shall have been paid in full.

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