Domain controllers don't really failover. They continuously replicate Active Directory data between each other so if one goes down, you have another one that has the same Active Directory information that you can use; therefore, your domain will still function.
However, other services like DNS and DHCP will go down with the server. That is why it is best to provide a seconday DNS server.
Last Wiki Answer Submitted: June 4, 2009 4:21 am by mshen27,310 pts.