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Problems Resolving

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  • Problems Resolving


    Interesting little problem here. We seem to be having problems resolving We issue a NSlookup for and it returns the info, we do it again and we get no response. Only when we clear the cache on the DNS server will it return the information, but one time only. Our DNS server is on a Windows 2003 box and is sat behind a CISCO877. Now if replace the cisco877 with another router, then there is no problems resolving

    This is the only domain we can see has this problem.

    Any ideas?



  • #2
    Re: Problems Resolving

    Are there any settings on the CISCO877 (acl's or inspect statements) related to DNS? Are there any such settings on the replacement router?


    • #3
      Re: Problems Resolving

      Complete these steps to troubleshoot this problem:
      1. Ensure the router can reach the DNS server. Ping the DNS server from the router using its IP address, and make sure that the ip name-server command is used to configure the IP address of the DNS server on the router.
      2. Use these steps to ensure that the router forwards the lookup requests:
        1. Define an access control list (ACL) that matches on DNS packets:
          access-list 101 permit udp any any eq domain
          access-list 101 permit udp any eq domain any

        2. Use the debug ip packet 101 command.
          Note: Ensure that you specify the ACL. If you enable the debug ip packet command without an ACL may produce a large amount of output to the console and cause the router to reload.

      3. Ensure you have the ip domain-lookup command enabled on the router

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