When a multicast forwarding entry (that is, an mroute) is added with an outgoing interface (OIF) on a port, the OIF count for that port is incremented. If you configure a port limit, and the OIF count on the port exceeds that limit, no OIFs on that port are added to mroutes (that is, OIFs are blocked).
mroute port limit
- host1(config)#mroute port 3/0 limit 10