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: 29 Aug 2014 - Revision: 1

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