This read-only Counter64 counts messages the router-side logic discarded because a join arrived on a port that is configured as a router port. This specifically flags a join coming in from the "wrong side" of the network — where the multicast router itself should be — which is usually a topology or port-role misconfiguration rather than a subscriber issue; because it is drawn from this instance's running statistics bin, it behaves like a long-running total rather than a rotating window, so admins baseline against it instead of expecting it to reset daily. On a metro aggregation uplink carrying several video EVCs, a count of 2,874 over the current statistics window 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.