UPDATE May 2016, seeing similar problem in the wild this year with NEW Dell PowerEdge R730 server Broadcom/QLogic 1Gbe NIC, Server 2012 R2 OS. NEITHER Hyper-V NOR Teaming were used. Latest Dell OMSA (OpenManage Server Administrator GUI) reported healthy system (no critical firmware updates needed). Get-NetAdapterVmq reported $False for all NICS. ADVANCED NIC SETTINGS showed BOTH VMQ AND FLOW CONTROL were enabled within the NIC driver – DISABLING BOTH resolved the issue for us immediately on this system. Problem showed up ONLY under network load (robocopy command, seeding new file server from old file share across network).
Broadcom / QLogic NIC’s on Hyper-V servers can cause significant network performance issues for both the host and guest virtual machines. There is a potential to resolve the issue with driver and firmware updates if a fix has been released by your hardware manufacturer. For many users the solution seems to be a workaround to disable VMQ for all Broadcom network interfaces and teams in the system.
Microsoft, Dell, and numerous other hardware/software vendors have confirmed the issue and suggested workarounds. If you’re running Windows Server 2012 R2, I recommend using the new Powershell Get/Set-NetAdapterVMQ commands.
Get-NetAdapterVmq # look for problem broadcom adapters or teams with VMQ true (enabled)
Set-NetAdapterVmq -Name NIC1,NIC2,NIC3 -Enabled $False
Get-NetAdapterVmq # confirm that problem adapters have changed to VMQ false (disabled)
Another suggestion that has been repeated often for this type of issue – consider switching your Hyper-V network adapters to Intel or other hardware manufacturer with better Hyper-V compatibility history.
- KB2986895 – VMs Lose Network Connection on WS2012 or WS2012 R2 Hyper-V When Using Broadcom 1GbE NICs (aidanfinn.com)
- How To Avoid Common Networking Issues In Hyper-V (aidanfinn.com)
- Virtual machines lose network connectivity when you use Broadcom NetXtreme 1-gigabit network adapters (support.microsoft.com)
- Poor network performance on virtual machines on a Windows Server 2012 Hyper-V host if VMQ is enabled (support.microsoft.com)
- Windows Server: Slow Network Performance on Hyper-V Virtual Machines with Virtual Machine Queue Enabled (dell.com)