Ensure that that DNS is properly configured to resolve the hostname to IP as well as the other way around from IP to hostname. For example, the following commands should help verify that the hostname/IP resolution is being properly resolved through DNS:

• hostname -f (this command should show the full hostname including the domain part, e.g., testhost.mydomain.net)
• hostname -s (this command should show the short hostname without the domain part, e.g., testhost)
• hostname -i (this command should show the IP address of the host, e.g., 192.168.22.120)
• nslookup <full-hostname> (replace the tag <full-hostname> with the actual full hostname, the result should show the correct IP address as seen above in the command "hostname -i")
• nslookup <ip-address> (replace the tag <ip-address> with the actual IP of the host, the result should show the correct full hostname as seen above in the command "hostname -f")