Windows 2000 and Windows XP domain members query their domain controllers every 15 minutes for name discovery. In an environment of mature domains and trusted domains, increasing this interval will reduce load on the domain controllers. In an environment that has dial-up branch office sites, increasing the interval saves money.

The domain information returned by the discovery query is cached to allow the Windows shell to distinguish between fully qualified domain names and fully qualified computer names.

Windows 2000 and Windows XP support a legacy method of controlling the discovery interval:

1. Use the Registry Editor to navigate to:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanWorkstation\Parameters.

2. Edit or add Value Name DfsDcNameDelay, a REG_DWORD data type, and set the data value to a number between 15 and 360 minutes.

3. You must restart your computer for this setting to take effect.

Windows XP supports a Sets how often a DFS Client discovers DC's Group Policy Object at Computer Configuration / Administrative Templates / Network which can be applied to the domain or to an OU. Windows XP dynamically checks for updates to this discovery interval and does NOT require a restart.

The policy has a matching registry Value Name of DfsDcNameDelay, at
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\System\DFSClient.

When a Windows XP client starts, the policy for the DFS name discovery interval is checked, and checked again every refresh interval. If the policy exists, its' interval is used. If no policy exists, the legacy registry entry is checked. If neither exist, discovery happens every 15 minutes.

NOTE: If an invalid data value is detected, 15 minutes is used.

You can check the values in the cache by opening a CMD.EXE prompt and typing dfsutil /spcinfo. You can also flush the cache by typing dfsutil /spcflush.

NOTE: See 271374 - Windows NT 4.0 SP6 Clients Contact the PDC Every 21 Minutes.

NOTE: See 265395 - Windows 2000 Member Runs Discovery Every 15 Minutes.