UCS Nexus 1000V VMware ESXi 5.1 and Windows 2008 R2 with VMXNET3 paravirtual adapter

Based on VMware Knowledge base articles 2020567 and 2039495


Operating System Specific Adapter Policies

By default, Cisco UCS provides a set of Ethernet adapter policies and Fibre Channel adapter policies. These policies include the recommended settings for each supported server operating system. Operating systems are sensitive to the settings in these policies. Storage vendors typically require non-default adapter settings. You can find the details of these required settings on the support list provided by those vendors.


We recommend that you use the values in these policies for the applicable operating system. Do not modify any of the values in the default policies unless directed to do so by Cisco Technical Support.

However, if you are creating an Ethernet adapter policy for a Windows OS (instead of using the default Windows adapter policy), you must use the following formulas to calculate values that work with Windows:

  • Completion Queues = Transmit Queues + Receive Queues
  • Interrupt Count = (Completion Queues + 2) rounded up to nearest power of 2

For example, if Transmit Queues = 1 and Receive Queues = 8 then:

  • Completion Queues = 1 + 8 = 9
  • Interrupt Count = (9 + 2) rounded up to the nearest power of 2 = 16


VMXNET3 Driver and Windows Server 2008R2 Settings and commands in ESXi 5.1 and UCS Environment


Windows VMXNET3 Device Driver Parameters:

Rx Ring #1 Size: 4096

Small Rx Buffers: 8192

Receive Side Scaling: Enabled

Windows Server 2008R2 Registry Changes / Entries:

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters Value(DWORD): DisableTaskOffload = 1

Windows Server 2008R2  NETSH commands:

At an Administrator Command prompt:  netsh int tcp set global chimney=disabled

The command to show global interface TCPIP options is : netsh int tcp show global