This read-write INTEGER indicates whether the local system is itself a member of the group address represented by an IGMP cache entry on a given interface. An admin checks this to see if the router itself, not just downstream hosts, has joined a multicast group on that interface, for example for its own management or routing protocol traffic. For example, a value indicating true here would mean the router itself is a member of the group in this cache entry, not merely relaying membership on behalf of hosts behind it.