Q. I set a Virtual LAN (VLAN) tag on my Hyper-V virtual network, but none of the traffic from the guests is being tagged with the VLAN. Why not?

A. This is by design. The VLAN tag you specify as part of the virtual network configuration only applies to the parent partition's use of the NIC, not the guest's. If you want the guest virtual NIC to use a VLAN tag, you must specify the VLAN in the network properties of each guest virtual machine, which allows each NIC for each VM to have different VLAN tags.