A set of noDiscard(1) causes the port to submit all packets
received on the port to the forwarding process, regardless,
of the absence or presence of a VLAN tag in the packet.
A set of discardUntagged(2) causes the port specified by ctVlanPortNum
to discard all frames received that carry no VLAN classification
(i.e. any untagged frames or priority tagged frames). A set of
discardTagged(3) has no effect.