This read-only Counter64 counts IGMP packets received with a message type this switch's snooping/proxy code doesn't recognize. A steady count usually means a host or router on that segment is speaking a newer or vendor-specific IGMP variant, rather than signaling an active fault; because it is drawn from the lifetime bin, which keeps accumulating until an operator explicitly clears it, a sudden plateau on an otherwise busy instance is itself a signal — most likely that someone cleared the stats rather than that traffic actually stopped. On a residential VLAN used for multicast video delivery, a count of 3,489 over the 106 days since the counters were last cleared is the kind of number an admin would trend against the join/leave rate on the same port to judge whether it's normal channel-surfing or an anomaly worth a closer look.