Question : User logon Problems in 2008 Active Directory

I've got a network with two 2008 Standard R2 servers acting as domain controllers.

DC1 is the Primary controller with all FSMO roles
DC2 is the 'backup' controller.

Both controllers are Global Catalogue servers and run DNS services as well.

Users have DC1 as a primary DNS and DC2 as a secondary DNS.

When DC1 is down, users are able to log on to their workstations without a problem (DC2 obviously takes over the login process).  However, while DC1 was powered off, we tried logging on
to a workstation using an account never before used to log onto that workstation and the logon process failed for some reason.

We were not able to log onto any workstation with user accounts that have never before used to log on to the workstations.

Can someone explain if this is a normal behaviour ? I assume since the backup DC is running, we should be able to log into any workstation, using any account...

Thank you for your help!

Answer : User logon Problems in 2008 Active Directory

Did you check to see if the PC that you were trying to logon to had a valid IP address?  AD is replicated and DNS is replicated, however DHCP isn't.