Cannot resolve default server host for Torque, check server_name file

If you are encountering Torque Error something like

Cannot resolve default server host 
'headnode.cluster.com' - check server_name file.
pbsnodes: cannot connect to server headnode.cluster.com, 
error=150010 (Access from host not allowed, or unknown host)

To resolve this issues, you have to look at 3 possible mis-configured areas

1. Ensure your /etc/sysconfig/network reflect the correct hostname
2. Ensure your /var/spool/torque/server_name are the same for both head and compute nodes
3. Ensure the environment variable PBS_DEFAULT is reflecting the correct hostname. For my situation, I have placed the environment variable on /etc/profile.d/torque.sh

You should be able to eliminate the issue.