IPv6 network connectivity problems occur on a Windows Server 2008-based computer when the Network Load Balancing feature is enabled

When a static IPv6 IP address is configured on a network adapter, the subnet prefix length incorrectly changes from 64 to 128 on a Windows Server 2008-based computer. This problem occurs if the Network Load Balancing (NLB) feature is enabled. If Windows Server 2008 uses the IPv6 IP address over this network adapter, network connectivity problems occur.

This problem occurs because Windows Server 2008 removes the default IPv6 route when you bind the NLB or when the configuration changes on the NLB cluster node. Because Windows Server 2008 removes the default route, no appropriate route is found on the responding cluster node. Therefore, Windows Server 2008 drops some traffic that is destined for IPv6 dedicated IP addresses or for IPv6 virtual IP addresses on the NLB cluster.

To resolve this problem, install the following hotfix on each cluster node in NLB.

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.

Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the �Hotfix Request� page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix, you must have the Network Load Balancing feature installed on the Windows Server 2008-based computers.

Restart requirement

You must restart the computer after you apply this hotfix. If you applied the hotfix while this node was an active part of the NLB cluster, after you apply the hotfix and restart the cluster node, check that the service is running and that the service start type is set correctly. To do this, follow these steps:

1. Start a command prompt as administrator.
2. Type sc query wlbs, and confirm that the state is RUNNING. If it is not, start the service by running the following:
   net start wlbs
3. Type sc qc wlbs and confirm that the start type is SYSTEM_START. If it is not, set it to system by running the following command.
   sc config wlbs start= system
   Note There is a space before �system.�
4. Open NLB Manager on the node, and then confirm that all nodes are converged. You might have to refresh the cluster state.

Note You should also follow these steps if the hotfix is uninstalled.

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 Vista and Windows Server 2008 file information notes

The .manifest files and the .mum files that are installed in each environment are listed separately in the "Additional file information for Windows Server 2008 and for Windows Vista" section. These files and their associated .cat (security catalog) files are critical to maintaining the state of the updated component. The .cat files are signed with a Microsoft digital signature. The attributes of these security files are not listed.

For all supported x86-based versions of Windows Server 2008

For all supported x64-based versions of Windows Server 2008 and Windows Vista

For all supported IA-64-based versions of Windows Server 2008

To work around this problem, add the default route on every NLB cluster node. You should take this action every time any configuration change occurs on the NLB cluster.

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

Additional file information for Windows Server 2008 and Windows Vista

Additional files for all supported x86-based versions of Windows Server 2008 and Windows Vista

Additional files for all supported x64-based versions of Windows Server 2008 and Windows Vista

Additional files for all supported IA-64-based versions of Windows Server 2008