Patent ID: 8270319

Claim:
A method for ensuring that multicast packets follow a same loop-free path as a path followed by unicast packets in a packet communication network, the packet communication network including at least one first area defined by a first level, each first area including a first plurality of nodes interconnected by a first set of links, each first area interconnected through at least one area border node to a second area defined by a second level, the second area including a second plurality of nodes interconnected by a second set of links, each area border node having at least one first level port connected to the at least one first area and a second level port connected to the second area, each multicast packet forwarded over the loop-free path including a header having a root-id identifying a root of a multicast tree, the method comprising: receiving at least one data packet at an area border node; and responsive to receiving a multicast packet at a second level port of an area border node: examining the root-id of the multicast packet; determining whether the multicast packet is to be forwarded on at least one of the first level ports of the area border node; and responsive to determining that the multicast packet is to be forwarded over at least one of the first level ports, substituting a different root-id into the packet before forwarding the packet over the at least one first level port.