The PVID indicates a VLAN to which the virtual network device needs to be a member, in untagged mode. In this case, the vsw device provides the necessary tagging or untagging of frames for the vnet device over the VLAN specified by its PVID. Any outbound frames from the virtual network that are untagged are tagged with its PVID by the virtual switch. Inbound frames tagged with this PVID are untagged by the virtual switch, before sending it to the vnet device. Thus, assigning a PVID to a vnet implicitly means that the corresponding virtual network port on the virtual switch is marked untagged for the VLAN specified by the PVID. You can have only one PVID for a vnet device.
The corresponding virtual network interface, when configured using the ifconfig(1M) command without a VLAN ID and using only its device instance, results in the interface being implicitly assigned to the VLAN specified by the virtual network's PVID.
For example, if you were to plumb vnet instance 0, using the following command, and if the pvid= argument for the vnet has been specified as 10, the vnet0 interface would be implicitly assigned to belong to the VLAN 10.
# ifconfig vnet0 plumb