Microsoft KB Archive/177883

= DNS Server Stops Using Round Robin for Host Name Resolution =

Article ID: 177883

Article Last Modified on 2/23/2007

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APPLIES TO


 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows NT Server 4.0 Standard Edition

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This article was previously published under Q177883



IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.



SYMPTOMS
After you install Windows 2000 DNS or after you apply the latest Dns.exe, your Microsoft Windows NT Domain Name Service (DNS) server no longer responds to queries in a round robin fashion.

For additional information, please see the following articles in the Microsoft Knowledge Base:

ARTICLE-ID: 159310

TITLE : Updated Version of Dns.exe Fixes Several Problems

ARTICLE-ID: 168321

TITLE : Creating a DNS Record for a Host That Has 2 or More IP Addresses



CAUSE
The latest version of Dns.exe for Windows NT and Windows 2000 DNS server introduce a new feature, LocalNetPriority, that attempts to return Host resources that are local to the requestor instead of merely responding round robin.



Windows NT 4.0 Servers
WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.

By default, this feature is enabled and normal round robin responses will not occur. To return to round robin responses, you will need to use the following steps to disable the LocalNetPriority setting:
 * 1) Start Registry Editor (Regedt32.exe or Regedit.exe).
 * 2) Go to the following subkey:


 * 1) Create a new value using the following information:

NOTE: This value does not exist by default.
 * 1) Stop and restart the Microsoft DNS server service.

Windows 2000 Servers
By default, this feature is enabled, and normal round robin responses will not occur. To return to round robin responses, use the following steps to disable the LocalNetPriority setting:
 * 1) Open the DNS Management Console in Administrative Tools.
 * 2) Right-click  , and then click Properties.
 * 3) Click the Advanced tab.
 * 4) Clear the Enable Netmask Ordering check box.



MORE INFORMATION
The DNS server will attempt to offer the "best-fit" address in response to a DNS query. This best-fit is one that is determined to be on the same subnet as the requesting DNS Client.

The classfull address is used to determine if the record and the querying DNS Client are on the same subnet. This means only the first octet will be used for class A addresses, the first two octets for class B, and the first three octets for Class C addresses. If you have subnetted your address space, this may have a derogatory effect on round robin load balancing.

Keywords: kbnetwork kbprb KB177883

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