An integer identifier or tag ID for this VLAN A value of zero indicates
the default VLAN.
When VLANs are enabled, the value must be unique among subinterfaces
configured on the same underlying major VLAN interface.
If the VLAN ID is non-zero, then the usdVlanSubIfVlanUntagged field must
be disabled.
Cannot be changed if the subinterface has upper bindings.