The TCP Chimney Offload feature fails on all network adapters in Windows Server 2008 R2 or in Windows 7 if you disable or change the properties of a network adapter

Consider the following scenario:

• You install multiple network adapters (NICs) on a computer that is running Windows Server 2008 R2 or Windows 7.
• You enable the TCP Chimney Offload feature on the computer.
• You change the properties of a network adapter, or you disable a network adapter.

In this scenario, the TCP Chimney Offload feature fails on all existing network connections, and the computer may stop responding because of a high network load.

Additionally, the existing network connections on the other NICs are in the InHost state instead of the Offload state if you run the netstat -ton command. For example, you receive the following output:Note This issue affects only the existing network connections on other network adapters. This issue does not occur if you create a new network connection.

This issue occurs because an interface parameter is not received in the reauthorization by Windows Filtering Platform (WFP) Application Layer Enforcement (ALE). Therefore, the TCP Chimney Offload feature stops on the existing network connections. Additionally, the computer stops responding when the network load is high.

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 one of the following operating systems:

• Windows 7
• Windows 7 Service Pack 1 (SP1)
• Windows Server 2008 R2
• Windows Server 2008 R2 Service Pack 1 (SP1)

Registry information

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

Restart requirement

You must restart the computer after you apply this hotfix.

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 7 and Windows Server 2008 R2 file information notes

Important Windows 7 hotfixes and Windows Server 2008 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 7/Windows Server 2008 R2" 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, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:

  Version	Product	Milestone	Service branch
  6.1.760 0.20xxx	Windows 7 and Windows Server 2008 R2	RTM	LDR
  6.1.760 1.21xxx	Windows 7 and Windows Server 2008 R2	SP1	LDR

• 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 R2 and for Windows 7" section. MUM 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 7

For all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

Workaround for Windows 7 and for Windows Server 2008 R2

To work around this issue, use one of the following methods:

• Run the netsh int tcp set global chimney=disabled command to disable the TCP Chimney Offload feature.
• Run the net stop BFE command to disable the Base Filtering Engine (BFE) service.

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: For more information about WFP, visit the following Microsoft Developer Network (MSDN) website:
For more information about ALE reauthorization, visit the following MSDN website:
For more information about the netstat command, visit the following Microsoft TechNet website:
For more information about how to use the netsh commands to enable or disable the TCP Chimney Offload feature, visit the following Microsoft TechNet website:

Additional file information

Additional file information for Windows 7 and for Windows Server 2008 R2

Additional files for all supported x86-based versions of Windows 7

Additional files for all supported x64-based versions of Windows 7 and of Windows Server 2008 R2