Poor network performance in VM when creating a virtual switch and using broadcom NIC with Windows Server 2012

This issue is resolved please read post: http://datacenter-flo.de/?p=2050


Some customers reported me about performance issue with virtual machines running on Hyper-V V3 (Windows Server 2012) after creating a switch.

Together with colleagues we found out that the issue only appears with Broadcom network interface cards.

We saw that the issue is related by “Virtual Machine Queues” enabled on the networkadapter.

If you are facing this issue, please try to disable “Virtual Machine Queues” first on the virtual NIC in your VM. If this doesn’t resolve your issue, please disable “Virtual Machine Queues” also on the physical NIC of your server.

The issue should be fixed with a Broadcom firmware and driver update for the NIC.

You can do this in the Adapter Properties of the Network Interface Card.

Adapter Properties in BASC

Adapter Properties in BASC

Adapter Properties of a NIC

Adapter Properties of a NIC



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10 Responses to Poor network performance in VM when creating a virtual switch and using broadcom NIC with Windows Server 2012

  1. Charbel N. says:

    Dear Florian,

    Hope you are doing well.

    I have a question please:
    I have 2 HP Proliant servers with 8 NICs each 1Gbps, I Teamed 4 NICs as one group and the other NICs as second group, each TEAM group = 4Gbps, connected to 1Gbps Cisco switch:
    Teaming mode: LACP – Load Balancing Mode: Hyper-V Port – All Active.

    I am migrating VMs between the two nodes but I noticed that the network throughput is only 1Gbps, I suppose to reach 4Gbps, right?
    Could you please advise?

    Thank you and regards,

    • Flo says:

      Hi Charbel,

      when you use Loadbalancing you do not trunk 4 1GBit to 1 “virtual” 4GBit NIC. You have 4 singel NIC 1GBit NICs that share traffic, cover each other when one failes or load is high on this NIC. Normally you use Load Balancing for NIC Faileover or when you need low latency but not for high bandwidth.

      If you want to get the 4GBit bandwidth you need to configure Link Aggregation (also named as port trunking, link bundling, Ethernet/network/NIC bonding or NIC teaming)


      I hope this helps.

      Best regards

  2. Andy says:

    Hi Florian,

    I thought i’d ask Broadcom as i couldn’t see any driver update. I discovered that for own case it is probably down to a 1GB network needing different settings:


    If this is referred to VMQ then user needs to add the registry key to work.


    To enable VMQ on a management operating system with physical network adapters less than 10 Gbps


    Thought this worth sharing


    • Flo says:

      Hi Andy,

      thank you for the info.
      I have inofficial information that broadcom will deliver a driver to fix this issue in june or july.

      Best regards

  3. Ruud says:

    Hi Flo, have you any reference about this issue, like a bug or KB number or something. We want to pursue this with our vendor. Thanks!
    Regards, Ruud

  4. Pingback: FIX: Slow performance for Hyper-V VMs when using VMQ with Broadcom NICs - Flo's Datacenter Report

  5. Pingback: VirtualBrainz | FIX: Slow performance for Hyper-V VMs when using VMQ with Broadcom NICs

  6. Mark Jones says:

    June 2014 – confirming this is STILL an issue, even with latest Broadcom firmware and drivers from Dell’s website.

    Awful network performance from 3 x 1Gb Broadcom NIC team, until I disabled all 3 VMQ options in the driver for the Team adapter.

    No other change required.

    • Flo says:

      Did you also try the drivers from Broadcom website? I tested it serveral times with customers and Hans Vredevoort. It looked like it was fixed. I had some R610, R710, R620 and R720 for testing.

      The only thing I noticed was, that when you install the update pack, the issue still stays. I needed to uninstall the old Broadcom driver and install the harddrive pack.

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