What is Connection-Specific DNS Suffix?

Why can't we join our Windows XP machine to our Win2003DC's domain without adding the ".com" suffix?

• Why can't we join a brand-spankin-new, from-scratch-install-of Windows-Xp-Sp2 machine to a brand spankin new Win2003 Domain without needing the .com suffix? Basically, we've got a switch set up, with a couple test pc's all plugged into it (and we're sure all the ports are good, nics are good, etc). There's no other domains, it's not part of another network, not of the systems were ever part of another network. There's nothing on 'em but the o.s. I.e., if we create the machine we are going to add, first, on the server in AD, then try to join it to the domain from the XP box, it says "no domain controller can be found". UNLESS! we add the ".com" suffix to the domain name. Then we can join just fine. What is also weird is - if we then make say, another from-scratch test system, and install Windows Server 2003 on it, instead of XP,and say, just make that a file server - THAT system can join the test DC's domain just fine. No need for the .com suffix. DNS is live on the DC (this is a test mini domain we're using, with only a single brand new DC), and the XP box easily gets a DHCP'ed IP from the DC. ???

• Answer:

  have you configured the windows firewall on the server? if not it is the cause of your problem. the default configuration will prevent AD authentication to the machine.