Dell NetWorker 19.9 Administration Guide

Using the nslookup command

Use the nslookup command to verify that each DNS Server used by the source and destination hosts, correctly and consistently resolves both hosts by the short name, FQDN, and IP address.

1. Determine the Primary and Secondary DNS Servers that the host uses for name resolution:

   • On UNIX, review the /etc/resolv.conf file.

   • On Windows, type the following command from a command prompt:

     ipconfig /all
2. Use the nslookup command in interactive mode to validate forward name resolution lookups with the Primary DNS Server:
   1. From a command prompt, type: nslookup
   2. At the nslookup command prompt, specify the following values:

      Shortname_of_source_host
      FQDN_of_source_host
      IP_address_of_source_host
      Shortname_of_destination_host
      FQDN_of_destination_host
      IP_address_of_destination_host
      
      

      NOTE:It is recommended that you resolve every name and IP address for each host three times to ensure that successive queries return correct and consistent values.
3. Complete the following steps when the host uses multiple DNS Servers for name resolution:
   1. Change the DNS Server that nslookup uses for name resolution.

      In this example, the ipconfig /all command on a Windows host returns two DNS Servers, the Primary DNS Server 10.5.5.10, and secondary DNS Server 10.5.5.11.

      To configure nslookup to use the IP address 10.5.5.11, type the following commands:

      C:\>nslookup
      Default Server:  lad.corp.com
      Address:  10.5.5.10
      > server 10.5.5.11
      Default Server:  dmd.corp.com
      Address:  10.5.5.11

   2. At the nslookup command prompt, specify the following values:

      Shortname_of_source_host
      Shortname_of_source_host
      Shortname_of_source_host
      FQDN_of_source_host
      FQDN_of_source_host
      FQDN_of_source_host
      IP_address_of_source_host
      IP_address_of_source_host
      IP_address_of_source_host
      Shortname_of_destination_host
      Shortname_of_destination_host
      Shortname_of_destination_host
      FQDN_of_destination_host
      FQDN_of_destination_host
      FQDN_of_destination_host
      IP_address_of_destination_host
      IP_address_of_destination_host
      IP_address_of_destination_host

      NOTE:It is recommended that you resolve every name and IP address for each host three times to ensure that successive queries return correct and consistent values.
4. Use the nslookup command in interactive mode to validate reverse name resolution lookups in the reverse lookup zone with the Primary DNS Server:
   1. From a command prompt, type: nslookup.
   2. In the nslookup command prompt, type:

      set q=ptr

   3. At the nslookup prompt, type:

      IP_address_of_source_host
      IP_address_of_destination_host