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Poor network performance on virtual machines on a Windows Server 2012 Hyper-V host if VMQ is enabled

Symptoms
Consider the following scenario:
  • You have a Windows Server 2012 Hyper-V host that uses a Broadcom network adapter.
  • You create a virtual switch that binds to the network adapter.
  • You enable virtual machine queue (VMQ) on the Hyper-V host.
In this scenario, you experience poor network performance on the virtual machines that are hosted on the Hyper-V host.
Cause
This is a known issue with Broadcom network adapter drivers when VMQ is enabled. The following Broadcom network adapters are affected:
  • 57712
  • 57800
  • 57810
  • 57840
Resolution
Broadcom is aware of this issue and will release a driver update to resolve the issue. Until the driver update is available, you can work around the issue by taking one of the following actions:
  • Disable VMQ on the Virtual Network Adapter by using the following Windows PowerShell cmdlet:
    Set-VMNetworkAdapter –ManagementOS -Name <VirtualNetworkAdapterName> -VmqWeight 0
    Note If the problem is not solved, disable VMQ on the Broadcom network adapter.
  • Change the Media Access Control (MAC) address of the virtual switch.

    Note IP address of the Hyper-V host may change if DHCP is used.

    If you use System Center Virtual machine Manager (SCVMM), SCVMM can automatically assign a new MAC address.

    To manually assign a MAC address, follow these steps:
    1. Assign a MAC address by using the following Windows PowerShell cmdlet:
      Set-VMNetworkAdapter –ManagementOS -Name <VirtualNetworkAdapterName> -StaticMacAddress <MacAddress>
    2. Assign a dynamically generated MAC address by using the following Windows PowerShell cmdlet:
      Set-VMNetworkAdapter –ManagementOS -Name <VirtualNetworkAdapterName> -DynamicMacAddress
  • If there is another unaffected network adapter on the Hyper-V host, bind the virtual switch to that network adapter.
Third-party information disclaimer

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
Properties

Article ID: 2902166 - Last Review: 08/29/2014 21:00:00 - Revision: 3.0

Windows Server 2012 Datacenter, Windows Server 2012 Standard

  • kbtshoot kbexpertiseadvanced KB2902166
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