WINS Prepend1BTo1CQueries Feature Aids Load-Balancing Between Domain Controllers (269424)

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SYMPTOMS

The Windows 2000-based Primary Domain Controller (PDC) emulator may experience heavy usage and clients may needlessly direct requests to the PDC emulator. When this occurs, the load is not being distributed to other domain controllers.

Note that there can be many reasons for this behavior. This article describes one. For additional information about another possible cause, click the article number below to view the article in the Microsoft Knowledge Base:

258068 Windows 2000 PDC Emulator's CPU Spikes When Large Number of KRB_AS_REQs Are Sent from the BDC

CAUSE

To find a list of domain controllers in domain, a client may perform a WINS query for Domainname(1C). This list contains up to 25 domain controllers. By default, the WINS server adds the Domainname(1B) record to the beginning of the list. This is the special entry for the PDC emulator in a domain. Therefore, the primary domain controller is always the first entry in the Domainname(1C) list. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

167365 The Order That WINS Returns 1Ch Entries

RESOLUTION

To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack

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

   Date     Time       Version        Size     File name
   -----------------------------------------------------
   2-15-01  7:38:13PM  5.0.2195.2870  151,312  Wins.exe

Removing the (1B) Entry for the PDC

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

You can cause the WINS server to remove the (1B) entry for the PDC from the domain controller list. To do so, install this hotfix on each Windows 2000-based WINS server in your environment, and then make the following registry change on each Windows 2000-based WINS server in your environment:

Start Registry Editor (Regedt32.exe).
Locate and click the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlset\Services\WINS\Parameters
On the Edit menu, click Add Value, and then add the following registry value:
Value name: Prepend1BTo1CQueries
Data type: REG_DWORD
Value data: 0 = Disable, 1 = Enable
Quit Registry Editor.

Note Also, by default, WINS does prepend 1C queries with the corresponding 1B record. If one creates this registry key and sets it to "0", only then will WINS respond to 1C queries without prepending the list with the corresponding 1B record.

Note If this value is not present the behavior defaults to "enabled." This means that the 1B entry will be added.

MORE INFORMATION

Another useful method of distributing the load on domain controllers is to randomize the Domainname(1C) list. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

231305 WINS Randomize1cList Feature Aids Load-Balancing Between DCs

For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the article number below to view the article in the Microsoft Knowledge Base:

249149 Installing Microsoft Windows 2000 and Windows 2000 Hotfixes