TCP Chimney Offload and Virtual Machine Chimney Compatibility with Other Applications and Features

Applies To: Windows Server 2008 R2

When TCP Chimney Offload or Virtual Machine Chimney offloads processing for a connection, other features or applications that depend on having direct access to the connection data might not work. For example, Network Monitor (Netmon) does not capture offloaded traffic. Other features, when enabled, might make specific connections ineligible for offload; for example, if an IPsec policy requires inspection of all packets in order to enforce an encryption algorithm, connections that have this policy applied cannot be offloaded.

The table below shows how TCP Chimney Offload and Virtual Machine Chimney are affected by other common programs and services.

Application or feature Compatible? Details

Windows Firewall


If Windows Firewall is configured to allow a specific TCP connection, connection processing will be offloaded; however, there is a known issue in Windows Server 2008 R2 with specific firewall rules where offloaded connections are uploaded and are not be offloaded again.

Other firewalls

Product specific

Some non-Windows firewalls products are compatible. For more information, see your firewall documentation.

IPsec policy


Processing for TCP connections that are part of IPsec policy are not offloaded so that IPsec can inspect packets.

Network adapter teaming, also known as load balancing and failover

Product specific

Some manufacturers’ network adapter teaming solutions are compatible. For more information, see the documentation for your teaming solution.



Network monitoring tools

Tool specific

Some network monitoring tools work alongside TCP Chimney Offload, but do not monitor connections whose processing has been offloaded.

Network load balancing


Cluster service


Processing for TCP connections that use the network fault tolerant driver (netft.sys) are not offloaded.

Network address translation (NAT) and Internet Connection Sharing (ICS)


If either of these features is enabled, processing for connections is not offloaded.