Well, to be honest, it may not matter much. Though, I'll defer to any networking experts that come along.
As far as linux is concerned, the only things it cares about are your IP address, your netmask, gateway, and DNS settings.
If all of the above are correct, it doesn't really matter what "domain" your machine belongs to. Any requests leaving your machine will resolve hostnames through your DNS. Any machines that need to communicate with your machine will resolve your machine's name through DNS as well. In other words, if your DNS server has the right name-to-IP database, there won't be any communication problems.
Now, that said...
I ran into problems using a LAN with ".local" suffix. It turns out that some (well intentioned?) developers for the Avahi
project trigger on the ".local" and try to use mDNS name resolution instead of traditional DNS for those names. This caused me some grief. I had a properly configured local DNS server running, but one machine continually had problems resolving internal hostnames: because avahi was stepping in and trumping normal DNS resolution.
This may not be your problem, but it might be worth a look.
If avahi is installed, you can try to uninstall it or modify the order of entries in your /etc/nsswitch.conf file (or wherever it is for Fedora) to remove mDNS or have it take place after normal DNS.
Hah! Or it could be a simple missing file