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Unauthorising all DHCP servers on domain

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  • Unauthorising all DHCP servers on domain

    Hi all,

    First time posting so please bear with me.

    I have a very strange situation with the authorised servers on our DHCP server.
    Recently I started as the IT Engineer here and getting to know the network.

    In essence we have two authorised servers, however there names don't match the IP address. The attached screen shot will help.

    But basically the server Tankgirl doesn't exist it, however the IP address it's using does. That IP address is our only domain server which happens to be CAMBSRV10.
    As you can seen on the screen shot it is also listed as authorised server with a completely random IP Address.

    So in essence I need to get one authorised server of CAMBSRV10 with the IP of

    My question is I know I could unauthorise both servers, but will I then lose my scope and reservations ? I realise that users wont be able to get a DHCP address without a authorised server so this would be done out of hours.

    But I don't really want to have to rebuild the scope etc.

    Any help much appreciated
    Attached Files

  • #2
    Re: Unauthorising all DHCP servers on domain

    The 169.254.x.x address is an indication, to me at least, that you have another NIC on that server that is enabled, but not configured correctly. Since most modern servers come with more than one NIC on the hardware, you should disabled all NICs that you do not plan on using. Do this first, then clean up DNS records.

    If needed, you can unauthorize and re-authorize any DHCP servers you need once you have cleaned all of this up. I wouldnt suggest that you unauthorize any servers as a first step, because once you unauthorize the DHCP server(s), they will no longer be able to service clients.

    As a note, an unauthorized DHCP server will not loose its configuration (server, scope settings). It simply cannot have the DHCP service start and service clients. There is another process called BINL which starts/stops DHCP based on its authorization status.
    JM @ IT Training & Consulting


    • #3
      Re: Unauthorising all DHCP servers on domain

      Thanks JM

      I have actually noticed this and disabled the spare NIC, I am still wondering why the previous admin didn't pair the NIC cards but heh thats for another day.

      I just want to confirm, you are saying that I can remove all the authorised DHCP servers without losing my scope details ?


      • #4
        Re: Unauthorising all DHCP servers on domain

        Yes, you can deauthorize and then authorize the server and you won't lose any of your configuration.

        If Tankgirl no longer exists then you might want to make sure there are no records for it in DNS. If Tankgirl was a domain controller then you should also make sure it's objects have been properly deleted from AD.

        Network Consultant/Engineer
        Baltimore - Washington area and beyond


        • #5
          Re: Unauthorising all DHCP servers on domain

          Correct. The authorization only controls whether or not the DHCP service will run. An Enterprise Admin is required for authorizing and unauthorizing.
          JM @ IT Training & Consulting


          • #6
            Re: Unauthorising all DHCP servers on domain

            Thanks all