Patent ID: 6917983

Claim:
A computer-readable medium having instructions for performing a method of multicast routing with a multicast capable router in a newtowrk including a plurality of routers, wherein only a subset of the routers are capable of multicast, comprising the steps of: receiving, at the multicast capable router, link state advertisements from routers in the network; examining, at the multicast capable router, each link state advertisement to determine whether the link state advertisement includes a multicast capable bit indicating whether an associated router supports multicast; employing the received link state advertisements for constructing a multicast routing table and a unicast routing table, the multicast routing table corresponding to a short path tree through only multicast capable routers, wherein the multicast routing table includes a plurality of routing entries, and wherein routing entries are placed in the multicast routing table only for link state advertisements having the multicast capable bit set indicating that the associated router is a multicast router; and performing reverse path forwarding using the multicast routing table in support of routing multicast packets, whereby the multicast capable router is able to recognize and forward a multicast packet that is received via a path that is not indicated as the shortest path in the unicast routing table.