When this is admitOnlyVlanTagged(2) the device will
discard untagged frames received on this port.
When admitOnlyUntagged(3), the device will discard any
frames with a VLAN tag. When admitAll(1), all frames are
accepted and untagged or Priority-Tagged frames received
on this port will be assigned to the PVID for this port.
This control does not affect VLAN independent BPDU
frames, such as GVRP and STP. It does affect VLAN
dependent BPDU frames, such as GMRP.