mxmone, I'm trying to figure out WHY you want to do this. I'm guessing that you want internal users to be able to access the server using its FQDN:
h**p://servername.domainname.com/.
If that's the reason, then why not just add a record to your internal DNS or to the Astaro: 'servername.domainname.com->192.168.4.5'
Cheers - Bob