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Remove Global Catalog from Exchange 2010 servers

If you plan to move the GC role from a exchange 2010 servers to another Active Directory member server in the domain, be aware that there is some registery  tweaks you should know of.

If Global Catalog was enabled on the Exchange 2010 server, the port for Exchange Adress book  have been set static in registery. When  you remove the Global Catalog role and restarts the server, MS Eschange Adress book service will not start and therfore mail clients without Cached exchange mode  have problems connecting to the Mailbox server.

You will see the error:

Unable to register the MSExchangeAB RPC interface. Failed with the error code The endpoint is a duplicate (1740)

To fix this locate this Registery:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NTDS\Parameters\NSPI interface protocol sequences]  and search for a port bind eg. 6004.

DO NOT toutch this if the server is global catalog, if it have been global catalog in the past, you can delete the key and restart the server.

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7 Comments  comments 

7 Responses

  1. RichB

    Many thanks, just the answer I needed as I completely locked all outlook clients out of exchange! Why oh why do people not follow the rules and put exchange on a DC anyway!

    • There is some cases where this can be useful, if it is a small environment with one file/print and one exhcange server then you can have redundancy for the Active Directory, DNS ++ or when running on single Microsoft SMB server this is a issus that pops up when you will migrate away from it.

      But i totaly agree with you on this..
      – if possible; then do not do this!

      • RichB

        Ah, have you rebooted the server after the removal? The registry entries return!
        I also have 6004 down as a ‘ValidPorts_Autoconfig_Exchange’ in RPC Proxy key and TCPIP Parameters reserved ports.
        Any ideas?

  2. Hi.
    Yes i have restarted the server numberous of times.
    I always do so after a change like this to make sure the Settings are permanent.

    Have you set this in safemode? if not try that.
    Another quick way around is to set the registry with Group policy by using the new preferences policy and aplying this custom policy to only the “infected” server.
    But this should be the absolutetly last things to try if nothing else works



  3. RichB

    Hmmm. I rebooted intially and it was fine. Had to do a reboot this morning and the keys came back so outlook clients failed! Removed them, rebooted and it still didn;t work! Ended up having to make the server a GC again! All working again.
    Am going to build new server and move all mailboxes as soon as I can.
    Thanks for your help.

  4. csimoes

    THANK YOU!!! THANK YOU!!!! THANK YOU!!!!! finally everythings back to normal. worked perfect for me.

    cheers from Pt

  5. removed the key, restarted, and the entire key and its value repopulated …as reported by others above. This is Exchange 2010 and Win2k8R2 AD DC GC (holds FSMO roles, tried to remove GC and hit this issue – returned as GC and all good)