How to setup a working local/private/fake dns-setup on 10.4.2 server?

Hello! I have troubles to configure internal dns on our Xserve. I would like to know how the named.local, private.lan.zone and named.conf have to look as an example so that i can find out the errors in the actual config. The server is behinda nat-firewall that has a static ip assigned. It's not necessary for dns-resolve but we want our own "private.lan". Using the gui doesn't work, hostname says the server is named server.private.lan but for example client logins fail when we use server.private.lan as directory entry, only 10.0.1.1 works here. So, what we did so far is we set up a zone, name is private.lan, give it 10.0.1.1 as ip and then added all clients with their names in the machine tab. I can provide the existing files from /named and the named.conf when i'm in lab tomorrow, but maybe someone did this in 10.4.2 server already and had success and may wants to help here..