How to Disable Transport Control Protocol (TCP) Checksum Offloading
Article ID: 152109
Updated On:
Products
Endpoint Protection
Network Access Control
Issue/Introduction
What are the steps for disabling TCP checksum offloading
Symptoms
Slow network throughput. Packet captures show many "Bad Checksum" packets. Server/Client communication problems.
Symptoms
Slow network throughput. Packet captures show many "Bad Checksum" packets. Server/Client communication problems.
Cause
Possible cause is TCP Checksum Offloading
Resolution
Disable TCP Checksum Offloading some of the following steps were taken from Microsoft article 88870 located here: http://support.microsoft.com/kb/888750
References
Symantec Endpoint Protection appears to cause networking problems with NICs using a TCP Offload Engine
- Click on <start><Control Panel><Network Connections>.
- Right-click on the applicable network connection and select “Properties”.
- Next to the name of the NIC being used, click on “Configure”.
- Now click on the “Advanced” tab.
- If the NIC’s checksum offloading can be configured through the GUI it will show up in the left-hand box. If it doesn’t show up, perform the following:
- Open “regedit” from the “run” line
- Browse to HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters and verify that “DisableTaskOffload=1” exists.
If it does not, or if it is set to “DisableTaskOffload=0”, add the registry key, or change to “DisableTaskOffload=1", respectively.
Please Note: One test box had a Broadcom NIC and experienced communication problems. In a packet capture, it was evident that checksum offloading was enabled, but when checked, the NIC properties Checksum offloading was not listed. After adding the key described in step 7 (“DisableTaskOffload=1”), the problem went away.
References
Symantec Endpoint Protection appears to cause networking problems with NICs using a TCP Offload Engine
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