Hyper-V Server 2016

[Exet]

Hi All,

 

Have 2 Hyper-V hosts setup with Server 2016. Have a guest vm running Windows Server 2016 (file server) which seems to be having intermittent performance issues.. slow for users to save work at times and sometimes slow access when browsing the shares. I have read numerous articles about broadcom network cards & hyper-v and disabling VMQ but no improvement. On the hyper-v hosts I am getting en error event 16945 MAC conflict: A port on the virtual switch has the same MAC as one of the underlying team members on Team Nic Microsoft Network Adapter Multiplexor Driver.

 

I get that in a NIC Team it will use one of the network adaptors mac address but then I am getting a duplicate mac address on my vethernet switch.. Do you think this maybe causing the issue?

 

Thanks

[sister_annex]

We had this recently. Depending on how you set up your hosts, Hyper-v creates a pool of MAC addresses that are dynamically assigned to vNICS when VMs are created.

 

If you go into hyper-v on each machine and look at the virtual switch manager you should see the MACs there. We had a number that ended up with the same pool thus when the VMs were created the same MAC was applied to different NICs. This caused the slowness that you described (and the event log messages)

 

Give that a go see how you get on

[Exet]

Thanks for the response.. Going to check that out now.

 

I have been thinking I am going to set the mac address on my vethernet on the hyper-v host to a different one so it is different to the NIC team one as this is how I interpreted the error message? Was your scenario like this?

 

Thanks again

[sister_annex]

AFAIK the MAC on your vEthernet switch is tied to the hardware you assigned it too (I may be wrong)

 

I would try your Hyper-V Virtual Switch settings first

[Exet]

I've looked in the hyper-v virtual switch settings for both nodes and they both appear to have different pools.

 

https://www.dell.com/support/article/uk/en/ukbsdt1/sln132131/windows-server-slow-network-performance-on-hyper-v-virtual-machines-with-virtual-machine-queue-vmq-enabled?lang=en

 

Looking at that link I am thinking of trying to change the mac address of the vethernet switch as I cannot see any mac conflicts with the vms

 

currently banging my head against the wall with this one.

[sister_annex]

Have you run a constant ping to the VM in question? Are you dropping packets?

 

VMQs can be a nightmare, and if you're using 1GBe then it's pretty much pointless - this article explains it really well: https://www.altaro.com/hyper-v/the-hyper-v-virtual-switch-explained-part-1/

[Exet]

Yea run a constant ping and all seems good >1ms

 

Totally turned off VMQs and no difference

[Exet]

Right so I changed the mac address of the vethernet switch restarted the machine and ran the powershell command and it had successfully changed... but I am still getting the error event mac conflict...grrrrr

 

Any help would be greatly appreciated. Thanks