Here's the problem. I have setup a secondary domain controller to use as a backup in case my primary controller ever has to be maintenanced or crashes unexpectedly. I have added the secondary controller to the existing domain and setup AD. It replicated the users etc. perfectly. When I setup the TCP/IP settings for the second machine, I gave it a static IP and pointed it at my existing DNS server on the primary domain controller. I installed a DNS server on the secondary machine and setup a new Forward Lookup Zone. After turning off my primary DC for a test run, my DHCP server on the secondary machine works great and clients are able to connect to the internet with no problems, however, I am unable to add client machines to the domain. They are unable to see the domain. I am relatively sure that this is a problem with the DNS server, but I do not know exactly what I need to change. Thanks!

I think that your DHCP-server gives clients IP address of the primary DC only in options "DNS server". Please, issue command 'ipconfig /all' on the CLIENT MACHINE (that you cannot add to the domain) and show here its output.

Hello, on the first installed DC/DNS, did you use the AD integrated DNS zones? If yes you have to configure NOTHING on the new isntalled server, so NO NEW forward lookup zone, instead installing the DNS server role, all DNS zone information will be replicated as the users/computers etc. between the DCs. Also if you configure the second DNS server for the existing domain without AD integrated zones it should become a secondary DNS server and replicate from the existing one, also NO NEW forward lookup zone will be created. So please describe in detail how DNS is configured. For all domain machines it is essential to have all domain DNS servers configured on the NIC and NONE else, like the IPSs one.Best regards Meinolf Weber MVP, MCP, MCTS Microsoft MVP - Directory Services My Blog: http://msmvps.com/blogs/mweber/ Disclaimer: This posting is provided AS IS with no warranties or guarantees and confers no rights.

I was able to fix it, apparently I needed to enable Zone Transfers for both of my Forward Lookup Zones. After that the "_msdcs" zone copied over to the backup dc and everything seems to work great.