Patent ID: 7924836

Claim:
A method of installing forwarding state in a link state protocol controlled network node having a topology database representing a known topology of the network, and at least two ports for communication with corresponding peers of the network node, the method comprising steps of: computing a unicast path from the network node to a second node in the network, using the topology database, and installing unicast forwarding state associated with the computed unicast path in a filtering database (FDB) of the node; detecting whether an unsafe condition exists, and, when an unsafe condition is detected, removing multicast forwarding state for multicast trees originating at the second node; subsequently, advertising a “safe” indication signal to each of the peers of the network node, the “safe” indication signal comprising a digest of the topology database; computing a multicast path through the network node to at least one destination node of a multicast tree originating at the second node; and installing multicast forwarding state associated with the computed multicast path in the filtering database (FDB) of the network node, when a predetermined “go” condition is satisfied; wherein the predetermined “go” condition comprises receiving respective safe indication signals from at least one peer node, each received safe indication signal containing a respective topology database digest matching that of the “safe” indication signal advertised by the network node.