Q. If I have several virtual machines (VMs) running on Hyper-V linked to the same external virtual network, when they communicate does the traffic actually get passed to the physical network card?

A. Hyper-V has various types of virtual networks. An external virtual network is one that's linked to an actual physical network device, enabling communication to the network that's connected to the network adapter. If you have multiple VMs connected to the same external network and they communicate with each other, a common question is whether that traffic actually get sent down to the physical network adapter that the external network is connected to.

The answer is no. Hyper-V is smart enough to optimize networking traffic and, providing it's unicast VM to VM traffic on the same Hyper-V host via the same external virtual network, the traffic is sent without ever hitting the physical NIC. If the VMs were on the same host but connected to different external virtual networks, this optimization wouldn't apply—the traffic would hit the network adapter and the underlying network.

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