This all depends on what version of the network controller software, and what options have been set. In many cases we are talking about an Active Directory server. There is a lot of information on this subject if you google for it ("mac active directory"). And MacOS X Hints has an
article on it.
PS... don't simply refer to this as a "domain". It is an Active Directory Domain. There are too many types of domains out there to simply say that. If you say it without specifying what you are talking about, then you should be talking about DNS domains, which you clearly are not in this case.