The source Vlan ID of the IP multicast layer 3 flows.
This object should be instantiated and set whenever
the 'vlan' bit of the associated cseFlowMcastQueryMask object
is on.
If the 'vlan' bit is set, and a Vlan ID is assigned to this
object, only flows belonging to that vlan will be contained
in the result table.
If the 'vlan' bit in the associated cseFlowMcastQueryMask object
is cleared, this object is ignored during the query, and all
flows will be considered regardless of their vlan IDs.