Name resolution may fail on a Windows Server 2003 DNS server if conditional forwarding is configured and if records have different TTL values

Consider the following scenario:

• Conditional forwarding is configured on a Windows Server 2003 Domain Name System (DNS) server.
• The conditional forwarder points to a DNS server in a parent domain.
• The zone of the parent domain and the zone of the child domain have different Time to Live (TTL) values that are configured.

In this scenario, the name resolution for a record in the child domain may fail. This problem disappears after you restart the DNS Server service for which conditional forwarding is configured. This problem will occur again after a while.

The DNS Server service in Windows Server 2003 caches DNS records for received queries. However, the TTL values of the name server records ("NS" records), of the Host records ("A" records), and of other records may not match. If the TTL value of the "A" record is much shorter than the TTL value of the "NS" record, this problem occurs after the TTL value of the "A" record expires.

The cache is cleared when the DNS Server service restarts. Therefore, this problem disappears after the DNS Server service restarts. This problem occurs again when the TTL value of the "A" record expires.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must have Windows Server 2003 Service Pack 1 or Windows Server 2003 Service Pack 2 installed on the computer. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Server 2003 with Service Pack 1, x86-based versions

Windows Server 2003 with Service Pack 2, x86-based versions

Windows Server 2003 with Service Pack 1, Itanium-based versions

Windows Server 2003 with Service Pack 2, Itanium-based versions

Windows Server 2003, x64-based versions

Windows Server 2003 with Service Pack 2, x64-based versions

To work around this problem, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type LameDelegationTtl, and then press ENTER.
5. Right-click LameDelegationTtl, and then click Modify.
6. Under Base, click Decimal.
7. In the Value data box, type the value that you want, and then click OK.
   
   Note The value that you type inside the Value data box is a TTL value that is measured in seconds. To work around this problem, you must set this TTL value to a value that is smaller than the TTL value of the "A" record. For example, if the TTL value of the "A" record is 1 hour, you can set the registry value to the following value:
   1800
   This value of 1,800 seconds is equal to 30 minutes.
8. Exit Registry Editor.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: