How does Windows Server 2008 resolve Domain Controller Load Balancing problems?
This article discusses a new Group Policy setting which solves the Load Balancing issues with the domain controllers.
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http://www.windowsnetworking.com/kbase/WindowsTips/WindowsServer2008/AdminTips/ActiveDirectory/HowdoesWindowsServer2008resolvesDomainControllerLoadBalancingproblems.html