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I have some of my Hyper-V VM's on a network segment that pushes a lot of UDP multicast traffic (several 100MBit/s).

Now, all Hyper-V Windows hosts actually see and count the traffic on the Ethernet ports without joining the multicast group. I can even capture the traffic with Wireshark without having joined the multicast group. This means, Hyper-V must pass the traffic to the NIC driver when the traffic should be ignored by the NIC itself.

On my ESXi VM's this is not the case - the MCAST traffing is only seen when the host joins the multicast group and some goes for bare metal hosts.

Any idea why/what Hyper-V is doing here and if this behavior can be changed?

TJF
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1 Answers1

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If you're using a NIC that doesn't support VMQ, or if you have VMQ disabled, then the NIC must be placed in promiscuous mode, which leads to the behavior that you're seeing.

Jake Oshins
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  • ah that explains it - VMQ is indeed turned off due to recommendation to resolve a separate performance related issue – TJF Apr 29 '16 at 14:30