“Try next closest site” group policy – the DC Locator in Windows

With Windows Vista / 7 / 8 the “DC Locator Algorithm” has been improved. However, it needs to be activated by a group policy (GPO) first. The article will tell you about the differences and how to configure the group policy

DC Locator Windows XP:

In the standard configuration each DC is not only registered in the “site-related”, but also in the “general” records of the DNS. If the selected domain controller is not accessible, the Windows XP client will search the DNS for any other DC. It will search any other DC from the list of DCs which are registered in the “general records”. (default: all).

In case of an error the Windows XP client might choose a very unfavourable DC, even one on another continent.

DC Locator Windows Vista / Windows 7 / Windows 8:

The improved new DC locator uses the Site-Link-Costs from the Sites & Services Configuration to select the closest DC.
If the Active Directory services are connected to a clean HUB/SPOKE structure the client will select the closest HUB server for a fall-back.

Configuration of the group policy “Try next closest site”

Policy:
  Computer Configuration/Policies/Administrative Templates/System/Netlogon/DC Locator DNS Records
Setting:
  Try next closest site
Value:
  Enabled