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  • Alternate DNS server not being used

    We've recently had some issues with our PDC (which is also the Preferred DNS server for all computers on our network). When the PDC is down, no one is able to resolve domain names. All computers on the network have an Alternative DNS server set to another DC, however, the DNS clients don't seem to utilize this alternate DNS server. Any ideas? This causes major issues (as you can imagine) since if this one machine is down, there is no DNS which means no AD.
    Drew Green
    MCITP:EA & Messaging 2010, MCSE:S, CCENT
    www.drewgreen.net

  • #2
    Re: Alternate DNS server not being used

    Does this secondary DNS server have the necessary zones? Are they replicating correctly and thus are they populated as would be expected?

    Is there a firewall blocking the necessary ports?

    Anything in the event logs on this server that might indicate a problem with DNS?

    What diagnostics have you done?
    Gareth Howells

    BSc (Hons), MBCS, MCP, MCDST, ICCE

    Any advice is given in good faith and without warranty.

    Please give reputation points if somebody has helped you.

    "For by now I could have stretched out my hand and struck you and your people with a plague that would have wiped you off the Earth." (Exodus 9:15) - I could kill you with my thumb.

    "Everything that lives and moves will be food for you." (Genesis 9:3) - For every animal you don't eat, I'm going to eat three.

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    • #3
      Re: Alternate DNS server not being used

      No firewall, secondary server is also a DC w/ AD-integrated DNS (so yes to having the zone). Replication is fine. Nothing in the event viewer regarding dns. I haven't really known where to start regarding this, so lets say troubleshooting is at zilch.
      Drew Green
      MCITP:EA & Messaging 2010, MCSE:S, CCENT
      www.drewgreen.net

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      • #4
        Re: Alternate DNS server not being used

        Post the results ipconfig /all, dcdiag and netdiag on the faulty server. It should be pointing to itself for DNS, can you resolve anything on that server?
        Gareth Howells

        BSc (Hons), MBCS, MCP, MCDST, ICCE

        Any advice is given in good faith and without warranty.

        Please give reputation points if somebody has helped you.

        "For by now I could have stretched out my hand and struck you and your people with a plague that would have wiped you off the Earth." (Exodus 9:15) - I could kill you with my thumb.

        "Everything that lives and moves will be food for you." (Genesis 9:3) - For every animal you don't eat, I'm going to eat three.

        Comment


        • #5
          Re: Alternate DNS server not being used

          Originally posted by dwtechnology View Post
          We've recently had some issues with our PDC (which is also the Preferred DNS server for all computers on our network). When the PDC is down, no one is able to resolve domain names. All computers on the network have an Alternative DNS server set to another DC, however, the DNS clients don't seem to utilize this alternate DNS server. Any ideas? This causes major issues (as you can imagine) since if this one machine is down, there is no DNS which means no AD.
          Sorry, but I couldn't understand.

          When you say "domain names" do you mean than nobody can resolve FQDN or just names like PCNAME instead of FQDN PCNAME.DOMAIN.DOM

          Clear DNS cache, ofcourse.

          Run PING -a %IP ADDRESS OF secondary DNS%

          Run NSLOOKUP to see who is authorative.


          Check your DHCP configuration. Maybe falwty configuration of clients of secondary dns is causing problems.
          Last edited by kojo1984; 18th March 2011, 10:04.

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          • #6
            Re: Alternate DNS server not being used

            Originally posted by kojo1984 View Post
            Sorry, but I couldn't understand.

            When you say "domain names" do you mean than nobody can resolve FQDN or just names like PCNAME instead of FQDN PCNAME.DOMAIN.DOM

            Clear DNS cache, ofcourse.

            Run PING -a %IP ADDRESS OF secondary DNS%

            Run NSLOOKUP to see who is authorative.


            Check your DHCP configuration. Maybe falwty configuration of clients of secondary dns is causing problems.
            What happens is that internet domain names (web sites) and internal resolution does not work. I've not had the time to troubleshoot the specifics, as when this is happening I'm frantically trying to get the server back up rather than working with my users' workstations.

            Clearing the DNS cache is not an option, as I've got 75 workstations + a number of servers. I'll try ping -a next time this happens (hopefully not for a while ).

            I just went through my DC's and set the DNS client settings to use localhost as the primary dns server and the pdc as the alternate dns server. I read in a MS kb that this is the recommended config. It was all different across my DCs. I wonder if that's what the problem was. Time will tell.

            EDIT: Also wanted to add that DHCP is not the issue as most clients are statically configured.

            EDIT: Netdiag and dcdiag all passed (after I made those changes mentioned above; I don't know how it would have faired prior to that).
            Last edited by agreenbhm; 18th March 2011, 21:18.
            Drew Green
            MCITP:EA & Messaging 2010, MCSE:S, CCENT
            www.drewgreen.net

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            • #7
              Re: Alternate DNS server not being used

              OK... A suggestion... don't wait for problem to occur... configure one of the clients (use your PC) to use falwty DNS server as primary DNS server.




              Clear cache on that client, then try nslookup. Try pinging both names and domain names.

              Check does it work or not.



              The gforceindustries asked you can you browse from that server? Can you? Check for third party FW as geforceindustries said.



              Before some time, I've had similar problem. You should check DNS forwarders

              and do client have appropriate DNS suffix.

              Under TCP/IPv4 properties, under ADVANCED, check DNS tab if there is any config in there.

              And configure clients to obtain addresses automatically. You have to much clients for manuall config.

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              • #8
                Re: Alternate DNS server not being used

                I agree that we need to implement DHCP, however, we can't do that until after our busy season. The alternate DNS server is working just fine (I'm doing everything on my PC right now using that as the ONLY DNS server set up on my machine).

                The DNS suffix isn't set in the IP settings for clients, however, since they're all domain members, it's automatically set (in the System Settings -> Computer name).
                Drew Green
                MCITP:EA & Messaging 2010, MCSE:S, CCENT
                www.drewgreen.net

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