Disabling Checksum Offloading in Windows Server 2003


 

Note:  Rackspace no longer offers Cloud Servers with Windows 2003, but these instructions are here for legacy support purposes.

 

You may run into intermittent network connection problems or slowness on a server running Windows Server 2003, often after a server has been restored from a backup image. The problem can be caused by "checksum offloading", a feature designed to improve performance but which is known to have problems with certain network adapters (like the virtual adapters used by Cloud Servers).

Checksum offloading can be disabled with a registry change, creating a DisableTaskOffload entry in the subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Setting the value of the DNUM entry DisableTaskOffload to 1 will disable checksum offloading, 0 will enable it again.

A quick way to create the registry key is to do it from the command line.

  1. Open the Windows command prompt.

    The Command Prompt program should be visible in the Start Menu. If not, go to Start Menu > Run... and enter cmd.

  2. Use the REG command to create a registry entry that disables checksum offloading.

    We can create the registry entry we need from the command line by entering:

    REG ADD HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters /v DisableTaskOffload /t REG_DWORD /d 1
    
  3. Reboot the server.

    Checksum offloading will remain active until you reboot the server to make the new registry setting take effect.

You can make sure the registry entry is set by opening the Command Prompt and running:

REG QUERY HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters /v DisableTaskOffload

You should see a message saying the value of the entry is 0x1 (basically "1"):

Registry check results



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