Logon DC

Hi Everyone,

I have 2 DCs at the Head-office and one on Branch site, I've realized once the branch network goes down users all across even at the Head-office experience logon and email issues. When i run echo %LOGONSERVER% its shows the machine was authenticated by the DC @ the branch.

1.How can i set users @ Head-office to be logging on to the DCs on the LAN instead of branch DC.

2.How can i set users to be failing over automatically to the available DCs

Meshack