Method and apparatus for exchanging routing information and establishing connectivity across multiple network areas

method and apparatus for exchanging routing information and establishing connectivity across multiple network areas. method ensures that multicast packets follow the same cycle-free path followed by packets of peer-to-peer broadcast in a packet communication network. the network and communication includes at least a first area interconnected through at least one area edge node ("abn") to a second area. each abn has a first level port connected to each first area and a second level port connected to the second area. each forward multicast packet includes a header that has an id-rpta that identifies a route of a multicast tree. a data packet is received in an abn. responsive to receiving a multicast packet on a second-level port of an area edge node, the multicast packet-route id is examined and if the multicast packet is to be routed over at least one of the first-level ports , a different id-route is substituted inside the packet before the packet is forwarded over the first-level port.