A Windows Server 2003-based DNS server successfully resolves host names the first time, but then name resolution fails in later queries

Consider the following scenario.

• You use a Windows Server 2003-based DNS server to perform name resolution.
• Name resolution for some host names succeeds the first time.
• Name resolution for these host names fails during later requests.

In this scenario, users in the domain cannot access certain Web sites and file servers.

Note After the DNS cache is cleared, this problem no longer occurs.

This problem occurs because DNS in Windows Server 2003 does not correctly calculate the Canonical Name (CNAME) answer count.

A hotfix is available to resolve this problem.

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 (SP1) or Windows Server 2003 Service Pack 2 (SP2) installed on the server.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other previously released hotfixes.

Registry information

To use this hotfix, you do not have to make any changes to the registry.

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 SP1, x86-based versions

Windows Server 2003 with SP2, x86-based versions

Windows Server 2003 with SP1, IA-64-based versions

Windows Server 2003 with SP2, IA-64-based versions

Windows Server 2003, x64-based versions

Windows Server 2003 with SP2, x64-based versions

To work around this problem, clear the DNS cache. To do this, use one of the following methods.

Use a command-line tool

Use the Dnscmd.exe command-line tool to clear the DNS cache. To do this, follow these steps.

Note The Dnscmd.exe tool is included in Windows Server 2003 Support Tools. To install Windows Server 2003 Support Tools, right-click Suptools.msi in the Support\Tools folder on the Windows Server 2003 CD, and then click Install.

1. Click Start, click Run, type cmd in the Open box, and then click OK.
2. Type the following command, and then press ENTER:
   dnscmd /clearcache
   You receive the following message:
   completed successfully
   Command completed successfully.

Use the DNS tool

Use the DNS tool to clear the DNS cache. To do this, follow these steps:

1. Start the DNS tool. To do this, click Start, point to Administrative Tools, and then click DNS.
2. Under DNS, right-click the server on which you want to clear the cache, and then click Clear Cache.

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