A router having one or more downstream interfaces and situated in a data network system between sources that send multicast data packets to at least one multicast group address and multiple hosts that request data from the multicast group address and sources. In one implementation the router has a management system agent and an associated management system agent database and stores for each network interface, each multicast group address and each host information in the management system agent database derived from one or more data requests made by the hosts. In one implementation the router stores for a downstream network interface and multicast group address at least one INCLUDE source record containing information about include source lists derived by data requests made by the one or more hosts and at least one EXCLUDE source record containing information about exclude source lists derived by data requests made by the one or more hosts in the management system agent database, the router using a host-router multicast routing protocol based on the IGMP (Internet Group Management Protocol) or the MLD (Multicast Listener Discovery) protocol to communicate with the one or more hosts, the router using a different protocol to communicate with a management system control station information stored in the management system database.