I am trying to add a server as an additional DC to my existing domain. Towards the end of the AD installation process I get a Dc could not be contacted error

On running the netdiag /debug command I get a failed "DC list test". The test shows that my DC are not up, when they are online since I have joined my server to its domain and can successfully log into it.

Am I missing out anything on the DNS side???

It's probably DNS it's self that's the problem. Look at

DCDiag and NetDiag in Windows 2000 Facilitate Domain Join and DC Creation. Microsoft Knowledge Base Article - 265706

http://support.microsoft.com/?id=265706

Specificly look at Steps to Resolve Common Configuration Problems. Point #5

In the Preferred DNS server box, specify the IP address of the DNS server to which you want this computer to send DNS queries. Usually this is an existing DNS server in the same site. If this computer sends queries to the DNS server that is running on this computer, specify the IP address of this computer. Alternatively, in the Alternate DNS server box, specify an IP address of another DNS server to which you want this computer to send the queries if the Preferred DNS server does not respond.

(here is where most errors occur adding addiciotnal DC's, because the PC that you are joining doesn't find the Gloal Catalog and Authoritative Name Server, so it won't join). So, make sure this PC's DNS is pointing to the existing DC's IP.

Good Luck. The Article it's self is rather infomative..

Make sure there are subdomains in the DNS manager that are exact to this: http://www.khipset.net/spoofs/dnsub.jpg not the domain name itself, just those folders are subdomains in which contain service information for the DCs.... also check to be sure the RPC Service is started on the domain controller..