Improve Virtual Server Networking

Check out the Microsoft Scalable Networking Pack (KB912222) for ways to improve the networking performance of certain workloads and configurations in your virtual server environment.


1) you must have supported HW - the KB states "This feature pack requires hardware that is capable of supporting offload technologies as specified in this article. Without the appropriate offload hardware, no performance gains will be seen by using this feature pack. "

2) Reghacking required - the KB states: "The Windows Server 2003 Scalable Networking Pack updates the Network Driver Interface Specification (NDIS). After you install the update, there is no user interface to configure the options that are associated with the Windows Server 2003 Scalable Networking Pack. By default, the options are turned off. You can configure the options by using the Netsh.exe tool or by using the registry."

3) No worky with firewalls - the kb states: "TCP Chimney offload and NetDMA will not work with the following features:

• Windows Firewall
• Internet Protocol security (IPsec)
• Internet Protocol Network Address Translation (IPNAT)
• Third-party firewalls
• NDIS 5.1 intermediate drivers

If any one of these features is turned on, TCP Chimney offload and NetDMA will not work regardless of the registry settings.

By default, the IP NAT and IPsec Policy Agent features are turned on when certain components such as bridging and routing services are enabled. Therefore, TCP Chimney and NetDMA will not function in such a scenario. When the bridging and routing services are disabled, IPNAT is not turned off. Therefore, TCP Chimney or NetDMA is not re-enabled. The IP NAT and IPsec Policy Agent features must be explicitly turned off before TCP Chimney or NetDMA can function."

However, if you have the right hardware, don't need firewall 9and other above exclusions) - such as in some dev/test/training scenarios, then the Scalable Networking Pack may be just what you need :-). For example, this recent problem may be solved with the Pack:

Host OS: R2 64bit Windows 2003 w/SP1

Host NIC: Broadcom BCM5708C NetXtreme II GigE (NDIS VBD Client)



Windows 2003 Enterprise R2 w/SP1

Windows 2003 Standard R2 w/SP1

Windows XP SP2


Q: The host browser cannot reach any Internet sites nor can it renew its IP address but all the guests can surf the net and renew IP addresses. When the NIC on the host is repaired it can then surf the net and renew its IP but all the guests show network disconnected.


A: Install Microsoft Scalable Networking Pack (KB912222) on the host machine.

This may be related to the TCP offloading on the host NIC (KB888750).

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