Using Netsh Commands to Enable or Disable TCP Chimney Offload

Applies To: Windows Server 2008 R2

You use the interface TCP context of the netsh command-line tool to set the operating system mode for TCP Chimney Offload or to enable specific applications and ports for TCP Chimney Offload. The operating mode is global; that is, it applies to all network adapters connected to the operating system.

For more information about the commands listed in this section, see the Netsh commands for interface transmission control protocol on Microsoft TechNet.

Setting the operating system mode of TCP Chimney Offload

The operating system mode for TCP Chimney Offload is set to automatic by default in Windows Server 2008 R2 and to disabled by default in Windows Server 2008. See Using TCP Chimney Offload for information about the differences between automatic and enabled modes.

To set the operating system mode of TCP Chimney Offload

  1. To open an elevated Command Prompt window, click Start, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.

  2. At the command prompt, type one of the following commands and then press ENTER:

    • netsh int tcp set global chimney=automatic to set automatic mode (available only in Windows Server 2008 R2 and Windows 7)

    • netsh int tcp set global chimney=enabled to set enabled mode

    • netsh int tcp set global chimney=default to set the mode to the operating system default

    • netsh int tcp set global chimney=disabled to disable TCP Chimney Offload

Enabling and disabling TCP Chimney Offload for specific applications and ports

You can control what applications and ports TCP Chimney Offload will consider for offloading using the netsh tcp interface add and netsh tcp interface delete commands.

Important

The commands to enable and disable TCP Chimney Offload for specific applications and ports require that the Windows Firewall service and Base Filtering Engine (BFE) services are running. Before using these commands, ensure that the Windows Firewall service and BFE service are running. To start the BFE service, open an elevated command prompt, type net start bfe and then press ENTER. To start the Windows Firewall service, open an elevated command prompt, type netsh firewall set opmode enable, and then press ENTER.

To set all of an application’s ports eligible for offload

  1. To open an elevated Command Prompt window, click Start, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.

  2. Type netsh interface tcp add chimneyapplication enabledPathName, where PathName is the path to the application that you want to enable for offloading, for example c:\myapplication.exe.

To set all of an application’s ports ineligible for offload

  1. To open an elevated Command Prompt window, click Start, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.

  2. Type netsh interface tcp delete chimneyapplicationPathName, where PathName is the path to the application that you want to make ineligible for offloading, for example c:\myapplication.exe.

To set all connections on a specific port eligible for offload

  1. To open an elevated Command Prompt window, click Start, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.

  2. Type **netsh interface tcp add chimneyport enabled localport=**PortNum remoteport=*, where PortNumis the number of the port that you want to enable for offloading, for example 21.

To set all connections on a specific port ineligible for offload

  1. To open an elevated Command Prompt window, click Start, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.

  2. Type **netsh interface tcp delete chimneyport localport=**PortNum remoteport=*, where PortNumis the number of the port that you want to make ineligible for offloading, for example 21.