Connecting device using FQDN over subnets not working, IP is working.

Connecting device using FQDN over subnets not working, IP is working.

I have set up WDM 5.0 on a server 2008 VM. It has an external facing IP address. I have set up a Wyse device on another subnet, I input the external IP of the WDM, and the device checks in fine. I changed it to the FQDN, and it no longer checks in.

From the Wyse device, I can ping the FQDN, and it gets a reply with the correct external IP address of the WDM.

I would prefer to have the FQDN working, as we will be using this with a few clients.

Does anyone have any ideas, or things I should check?

Thank you in advance