DNS name resolution fails when using a long CNAME or DNAME chain record in Windows Server 2008

Applies to: Windows Server 2008 DatacenterWindows Server 2008 Datacenter without Hyper-VWindows Server 2008 Enterprise More

Symptoms


Consider the following scenario in a domain environment:
  • A Windows Server 2008-based DNS server is configured to perform name resolution.
  • The DNS server is configured to use root hints to resolve external domains.
  • A chain of CNAME records is configured on the DNS server.
  • Name resolution of some host names or important websites (such as download.microsoft.com) succeeds the first time.
  • The CNAME cache expires.
In this scenario, name resolution of these host names fails for all successive requests. Additionally, users in the domain cannot access certain websites or file servers.

Cause


This issue occurs because the DNS Server service in Windows Server 2008 incorrectly calculates the CNAME answer count.

Resolution


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 the problem described in this article. 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 be running Windows Server 2008 or Windows Server 2008 Service Pack 2 (SP2). Additionally, you must install the DNS Server role on the computer.

For more information about how to obtain a Windows Server 2008 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

968849 How to obtain the latest service pack for Windows Server 2008

Registry information

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

Restart requirement

You do not have to restart the computer after you apply this hotfix. To avoid restarting, stop the DNS Server service on the computer.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.
Windows Server 2008 file information notes
Important Windows Vista hotfixes and Windows Server 2008 hotfixes are included in the same packages. However, only "Windows Vista" is listed on the Hotfix Request page. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows Vista" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.
  • The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.
    VersionProductSR_LevelService branch
    6.0.600
    2.
    22xxx
    Windows Server 2008SP2LDR
  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008" section. MUM files and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.
For all supported x86-based versions of Windows Server 2008
File nameFile versionFile sizeDateTimePlatform
Cache.dnsNot Applicable3,17909-Sep-201111:25Not Applicable
Dns.exe6.0.6002.22736510,97601-Nov-201114:51x86
Dnsserver.events.xmlNot Applicable60909-Sep-201111:25Not Applicable
For all supported x64-based versions of Windows Server 2008
File nameFile versionFile sizeDateTimePlatform
Cache.dnsNot Applicable3,17915-Mar-201104:34Not Applicable
Dns.exe6.0.6002.22736638,97601-Nov-201114:11x64
Dnsserver.events.xmlNot Applicable60915-Mar-201104:34Not Applicable

Workaround


To work around this issue, perform one of the following methods:
  • Configure the ISPs DNS server to be the DNS forwarder instead of using root hints.
  • Upgrade the operating systems on the affected DNS servers to Windows Server 2008 R2.
  • Clear the DNS cache.
To clear the DNS cache, perform one of the following methods.

Use the DNS Server command-line tool

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

Use the DNS Manager snap-in tool to clear the DNS cache. To do this, follow these steps:
  1. Start the DNS Manager snap-in. 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.

Status


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

More Information


The following is a sample output when you run the nslookup command at an administrative command prompt on the DNS server:

Note The first DNS query is resolved successfully. However, the DNS server cannot resolve the host name for all successive DNS queries until the DNS Server service is restarted or the DNS cache is cleared.

First DNS query:
C:\Users\astrenadko>nslookup download.microsoft.com [the DNS server] Server: UnKnown  Address: 192.168.200.10  Non-authoritative answer:  Name: a767.ms.akamai.net  Addresses: 87.245.209.215  87.245.209.233  Aliases: download.microsoft.com  download.microsoft.com.nsatc.net  main.dl.ms.akadns.net  intl.dl.ms.akadns.net  dl.ms.georedirector.akadns.net 
Second DNS query:
C:\Users\astrenadko>nslookup download.microsoft.com [the DNS server] Server: UnKnown  Address: 192.168.200.10  Non-authoritative answer:  Name: download.microsoft.com 
For more information about a similar issue that occurs in Windows Server 2003, click the following article number to view the article in the Microsoft Knowledge Base:

945532 A Windows Server 2003-based DNS server successfully resolves host names the first time, but then name resolution fails in later queries

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

824684 Description of the standard terminology that is used to describe Microsoft software updates

Additional file information

Additional file information for Windows Server 2008

Additional files for all supported x86-based versions of Windows Server 2008
File nameX86_1d394ed64cd4ec9fe00006816a4bc7fe_31bf3856ad364e35_6.0.6002.22736_none_46fa6066fbfb0779.manifest
File versionNot Applicable
File size706
Date (UTC)02-Nov-2011
Time (UTC)11:34
File nameX86_microsoft-windows-dns-server-service_31bf3856ad364e35_6.0.6002.22736_none_505b9736eceb6035.manifest
File versionNot Applicable
File size163,376
Date (UTC)01-Nov-2011
Time (UTC)17:35
Additional files for all supported x64-based versions of Windows Server 2008
File nameAmd64_71721aa9ea70dc391b243f138cdefaaf_31bf3856ad364e35_6.0.6002.22736_none_a4d76236ecfd4f8c.manifest
File versionNot Applicable
File size710
Date (UTC)02-Nov-2011
Time (UTC)11:34
File nameAmd64_microsoft-windows-dns-server-service_31bf3856ad364e35_6.0.6002.22736_none_ac7a32baa548d16b.manifest
File versionNot Applicable
File size163,418
Date (UTC)01-Nov-2011
Time (UTC)16:12