PURPOSE

This Article helps determine if host name resolution is working on various computer systems (including A Windows system, a Linux system, and a Data Domain system).  And whether the resolution is local or from a server.

• Replication not working
• Replication lag
• Replication throttle not working
• Unable to connect to the Data Domain system from the media server
• Unable to mount to the data domain system
• System is sluggish
• System is unresponsive

APPLIES TO

• All Data Domain Systems
• All Software Releases
• Networking

SOLUTION

Name resolution is an important part of networking.  The system must be able to convert a Host name to an IP Address to be able to communicate on the network.  Some configurations are requiring reverse resolution set up as well to in order to authorize inbound connections. There are two types of resolution that will be examined.

• Local Hosts file
• DNS

1. Verify DNS configuration. To verify the DNS configuration, at the command prompt type:

   # net show dns
   #   Server
   -   -----------
   1   192.168.14.92
   -   -----------

   Changing or adding a DNS server. If the DNS server specified is incorrect, at the command prompt type:

2. net set dns <ip address>

   Example bellow configures a DDR to use two DNS servers, 192.168.19.42 and 192.168.19.43

   # net set dns 192.168.19.42 192.168.19.43
   The Name (DNS) server list is:
   192.168.19.42, 192.168.19.43

• Check if all the DNS servers are accessible by issuing a ping to each IP address listed as DNS server (output of net show dns command), example:

  # ping 192.168.19.42
  PING 192.168.19.42 (192.168.19.42) 56(84) bytes of data.
  64 bytes from 192.168.19.42: icmp_seq=0 ttl=128 time=1.89 ms
  64 bytes from 192.168.19.42: icmp_seq=1 ttl=128 time=0.132 ms
  64 bytes from 192.168.19.42: icmp_seq=2 ttl=128 time=0.114 ms

  ...

• If using local hosts file instead of DNS, check if all the hosts that are accessing the DDR are listed in the file by issuing the command net hosts show, example:

  # net hosts show

  Hostname Mappings:
  10.2.3.167 -> backup1.mydomain.local
  192.168.4.139 -> backup2.mydomain.local
  74.125.127.147 -> backup3.mydomain.local

• Check if the DNS domain name is set up properly. It can be used to host names in the same domain instead of FQDN (full-qualified domain name), example:

  # net show domainname

  The Domainname is: mydomain.local

After verifying that the name resolution is working, it is a good idea to make sure the Host name of the Data Domain system has been set.

• Check if a FQDN is being resolved into an IP address by issuing a ping command to the FQDN. Example:

  # ping backup.mydomain.local
  PING backup.mydomain.local (192.168.20.20) 56(84) bytes of data.

  ...

  Note the FQDN (backup.mydomain.local) was resolved to IP address (192.168.20.20).

hostname

1. Verify the hostname of the Data Domain System
2. Verify the hostname and look for the correct FQDN within the hostname.
    
3. Map the hostname to an IP address using net hosts add command.

   # net hosts add <ipaddress of client> <full host name of client> <short host name of client>

# net hosts add 10.2.3.167 backup1.datadomain.com backup1