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Issue with Packets Received Discarded errors on Hyper-V NIC

I'm looking for information on Packets Received Discarded errors. I know very little about what might cause this issue.

We have a HyperV Server with 2 physical NICs. One for the internal network (NIC1) and one of the management network (NIC2).

All of the VMs are on NIC1 (Internal Network) and the host is on NIC2 (Management Network). (you'll need to bear with me, as I'm not very up on HyperV either)

Basically there is an awful lot of Packets Received Discarded errors on NIC2 (Management Network).

Using Perfmon and - https://blogs.technet.microsoft.com/rmilne/2014/07/18/retrieving-packets-received-discarded-perfmon-counter-from-multiple-servers/ - I found that there were 785,710 Packets Received Discarded on NIC2 (Management Network) and none on NIC1 (Internal Network).

VMWare had a page on this for their product - https://kb.vmware.com/s/article/2039495 - that said the following:

This issue occurs when packets are dropped during high traffic bursts. This can occur due to a lack of receive and transmit buffer space or when receive traffic which is speed-constrained. For example, with a traffic filter.

NIC1 (Internal Network) has 100s of times more receive traffic than NIC2 (Management Network), which is why this is strange. There is hardly any traffic on NIC2 (Management Network) than on NIC1 (Internal Network).

I checked the Receive buffers in the advanced properties on NIC2 (Management Network) and it was set to 200, this was the same buffer size as NIC1 (Internal Network), which all the other VMs run on. Making this even stranger. This suggests that there is a lot of traffic going over NIC2 (Management Network), or that there is a fault on the NIC, as it is trying to fill up the buffer due to high traffic.

Does anyone know how this can be resolved or where to start looking at this?
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1 Solution
Philip ElderTechnical Architect - HA/Compute/StorageCommented:
Elevated PowerShell:

Get-VMSwitch | FL

Open in new window

Please post the results preferably in a CODE window.
CT08Author Commented:
Hi Phillip,

I have embedded images of the first two commands. The 3rd command wouldn't embed for some reason so I have just attached it as a file to this post.

Get-NetLbfoTeam didn't return any results at all. But nor did it fail, see the picture.

Thanks for your help.

Philip ElderTechnical Architect - HA/Compute/StorageCommented:
The result can be copied and pasted into a CODE window. It's much simpler to work with.

I have two very thorough Hyper-V EE articles:

Some Hyper-V Hardware and Software Best Practices
Practical Hyper-V Performance Expectations

I suggest reading them as they have a lot more info in them. The HP 331i is a Broadcom rebranded NIC. Please disable Virtual Machine Queues for _all_ physical ports on the server.

I suggest the following:

Team 0: Port 0 + 2 = Management Team Name: Management
Team 1: Port 1 + 3 = Dedicated vSwitch Name: vSwitch

Remove the current vSwitches, create the teams, then bind the Hyper-V virtual switch to the vSwitch and don't share it with the host OS.
New-VMSwitch –Name vSwitch –NetAdapterName “vSwitch” –AllowManagementOS 0

Open in new window

Then bind the vSwitch to the VMs.
CT08Author Commented:
Hi Phillip,

Thanks for the info.

I'll close this question for now and mark your answer as best answer.
CT08Author Commented:
Great info here Philip. Thanks.
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