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.


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Article ID: 2902166 - Last Review: Aug 29, 2014 - Revision: 1

Windows Server 2012 Datacenter, Windows Server 2012 Datacenter, Windows Server 2012 Datacenter, Windows Server 2012 Datacenter, Windows Server 2012 Standard, Windows Server 2012 Standard, Windows Server 2012 Standard, Windows Server 2012 Standard

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