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why does nslookup from the DNS server itself resolve differently?

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  • why does nslookup from the DNS server itself resolve differently?

    I am not sure if I have DNS configured correctly. I have the NIC of my DC pointed to itself (192.168.1.111) but when I launch nslookup from this DC the output looks strange to me (I did a test by querying for cnn.com)

    C:\windows\system32>nslookup
    Default Server: UnKnown
    Address: fc00::1
    > cnn.com
    Server: UnKnown
    Address: fc00::1
    *** UnKnown can't find cnn.com: No response from server
    >

    But when I launch nslookup from a client PC it appears like I would expect it to:

    C:\Users\Administrator.XXX-XXXX.000>nslookup
    Default Server: server1.home.mydomain.com
    Address: 192.168.1.111
    > cnn.com
    Server: server1.home.mydomain.com
    Address: 192.168.1.111
    Non-authoritative answer:
    Name: cnn.com
    Addresses: 157.166.226.26
    157.166.226.25
    >

    What is fc00::1 ? I know it's an IP v6 but on my NIC properties I have set to Dynamic (see attached for ipv4 and ipv6.) And of course the ipv6 issue brings up a whole lot of questions, especially with regard to how I should set up DHCP? Thanks for help.
    Attached Files

  • #2
    Re: why does nslookup from the DNS server itself resolve differently?

    IIRC fc00::1 is the IPv6 equivalent of the local loopback and since Server 2008 and above prefer IPv6 to IPv4, they will report that.

    My DNS servers are the same, and I have no problems with name resolution on them, so I would find something more important to worry about
    Tom Jones
    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
    PhD, MSc, FIAP, MIITT
    IT Trainer / Consultant
    Ossian Ltd
    Scotland

    ** Remember to give credit where credit is due and leave reputation points where appropriate **

    Comment


    • #3
      Re: why does nslookup from the DNS server itself resolve differently?

      You can remove the DNS entry from you IPv6 config if you like.

      As for why it's not resolving records, I imagine your DNS service is not bound to your IPv6 address. You can either bind it to the address (in the DNS console, server properties), or you can just leave it and no harm will come of it.

      more info:
      nslookup uses the primary DNS server by default so that is the IPv6 server.
      The reason you don't really see any DNS issues on the server is because it fails over to one of the IPv4 servers since the IPv6 DNS server isn't available.

      TMI?
      Regards,
      Jeremy

      Network Consultant/Engineer
      Baltimore - Washington area and beyond
      www.gma-cpa.com

      Comment


      • #4
        Re: why does nslookup from the DNS server itself resolve differently?

        Originally posted by Ossian View Post
        IIRC fc00::1 is the IPv6 equivalent of the local loopback and since Server 2008 and above prefer IPv6 to IPv4, they will report that.
        Actually, the fc00::/7 "Unique Local Addresses" block consists of two /8 blocks, and the use of the lower of these two, fc00::/8 is not yet properly standardized (Wikipedia article with links to relevant RFCs).

        I'd be really surprised to see a fc00::/8 address appear by default on a Windows system. Somebody must have entered it manually. I can see no good reason why that address should be there, and as there's probably going to be some sort of central authority managing these addresses, just grabbing "fc00::1" is definitely not a good idea.

        The IPv6 loopback address is "::1", by the way. That's the address that turns up when I run nslookup interactively on my 2008 R2 server.

        Comment


        • #5
          Re: why does nslookup from the DNS server itself resolve differently?

          Hi,

          I completely agree that you do not have any name resolution issues. Also the address that you see is a site local address.
          By default in Windows, IPv6 has preference over IPv4, so whenever you send a query for name resolution queries goes for both i.e. A and AAAA records.
          As the AAAA records does not exists in the DNS, you get a answer for IPv4.
          Disabling IPv6 from the NIC card is also not a good option as there are different dependencies on IPv6.

          Please follow the article microsoft kb article 929852 and you can do any one of the options that is accepted by you.

          Regards.
          Sandeep Suman

          Comment


          • #6
            Re: why does nslookup from the DNS server itself resolve differently?

            I changed the IPv6 address to fd9c:6db1:c7ae:8aef:c9f:72f5:23f5:111 (I used some IPv6 calculator that "converted" 192.168.1.111 to the IPv6 equivalent so on my servers I just change the last xx to the same as the ending on the 192.168.1.x. Now it looks like this:

            NSLOOKUP
            > disney.com
            Server: server1.xxx.mydomain.com
            Address: fd9c:6db1:c7ae:8aef:c9f:72f5:23f5:111
            Non-authoritative answer:
            Name: disney.com
            Address: 199.181.132.249
            >

            Would this present a problem for DNS? DNS isn't something I'm very adept with. Thanks for the help

            Comment


            • #7
              Re: why does nslookup from the DNS server itself resolve differently?

              Are you specifically using IPv6 on your network? If not then it doesn't really matter.
              Regards,
              Jeremy

              Network Consultant/Engineer
              Baltimore - Washington area and beyond
              www.gma-cpa.com

              Comment

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