Use Group Policy to configure clients to check for "stickiness" (continuing to use the next-closest domain controller, when the closest becomes available again). In Server 2008, a group-policy configurable time interval has the client machine do a new search to see if you're attached to your local domain controller. If not, it will attempt to reattach to it. You can learn more at this MSDN page: msdn2.microsoft .com/en-us/library/ ms675983.aspx.