Windows NT 4.0 SP6 Clients Contact the PDC Every 21 Minutes

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This article was previously published under Q271374

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SYMPTOMS

Microsoft Windows NT 4.0 may contact the primary domain controller (PDC) when you start your computer and every 21 minutes to get a Distributed File System (DFS) referral. When this occurs, there may be unwanted network traffic and unwanted load on the server service in larger domains.

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CAUSE

This problem can occur because there are changes to the Mup.sys file from Q242001. It is necessary to periodically check with a Microsoft Windows 2000-based domain controller for a DFS referral. Because Windows NT 4.0 Service Pack 6 (SP6) cannot locate a Windows 2000-based domain controller if one exists, it must contact the PDC. Note that the PDC is the only system in a domain that is guaranteed to be a Windows 2000 domain controller if any Windows 2000-based domain controllers exist.

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RESOLUTION

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS (http://support.microsoft.com/default.aspx?scid=fh;en-us;cntactms)

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English-language version of this fix should have the following file attributes or later:

   Date        Time     Version        Size     File name  Platform
   ----------------------------------------------------------------
   09/08/2000  01:33pm  4.0.1381.7086  80,848   Mup.sys    Intel
   09/08/2000  01:32pm  4.0.1381.7086  142,800  Mup.sys    Alpha

The Mup.sys file enables a new registry entry to be specified that can enable a delay. The delay is specified in minutes, starting at 21 minutes. When you enable this registry entry, the initial traffic when you start the computer is not prevented, however, the subsequent traffic is prevented.

Start Registry Editor (Regedt32.exe).
Locate and click the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanWorkstation\
On the Edit menu, click Add Value, and then add the following registry value:
Value Name: DfsDcNameDelay
Data Type: REG_DWORD
Radix: select Decimal
Value: Delay in minutes
Quit Registry Editor.

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