This read-only bitmask lists which ports have sent an IGMP report requesting inclusion of a specific multicast group, or group-and-source under IGMPv3, meaning those ports should receive the traffic. An administrator checks this to confirm which physical ports are actively subscribed to a given multicast stream. For example, if a multicast video isn't reaching a set-top box, checking rlIgmpSnoopMembershipIncPortlist for that group verifies whether the box's port is actually listed as included.