A Windows Server 2008-based DHCPv6 server consumes 100 percent of CPU resources and then becomes unresponsive after it receives a malformed relay-forwarded packet

Consider the following scenario:

• You enable the DHCP Server role on a Windows Server 2008-based server.
• An IPv6 scope is configured on this DHCP server to manage IPv6 IP addresses.
• Some IPv6 release or renew packages are forwarded by a DHCP relay agent.

In this scenario, the DHCPv6 server service may consume 100 percent of CPU resources and then become unresponsive to IP address release requests and to renew requests.

When this issue occurs, the DHCPv6 packets stall on the DHCPv6 server. In this scenario, you must restart the server.

The DHCPv6 packets stall on the server when the following conditions are true:

• The DHCPv6 server receives a relay-forwarded DHCPv6 packet that contains a DHCP INFORM message.
• This relay-forwarded DHCPv6 packet does not contain the Client Identifier option.

A client that is running Windows Mobile 6.1 is inclined to send DHCPv6 packets that do not contain the Client Identifier option.

To resolve this issue, install hotfix 967789 on the Windows Server 2008-based DHCPv6 server. After you install this hotfix, the server silently drops the relay-forwarded packets that do not contain the Client Identifier option, and then the server goes on to handle the next packet.

Hotfix information for Windows Server 2008

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, the computer must be running Windows Server 2008. Additionally, the DHCP Server role must be installed.

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 2008 file information note

The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately . MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files (attributes not listed) are signed with a Microsoft digital signature.

Windows Server 2008, x86-based version

Windows Server 2008, x64-based version

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

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

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

The Client Identifier option is documented in Request for Comments (RFC) 3736, "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6." To see RFC 3736, visit the following IETF Web site: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
For more information, click the following article number to view the article in the Microsoft Knowledge Base: