The following procedures occur at the root of the P2MP LSP (head-end or ingress LER node):
First, the P2MP LSP state is established via the control plane. Each leaf of the P2MP LSP will have a next-hop label forwarding entry (NHLFE) configured in the forwarding plane for each outgoing interface.
The user maps a specific multicast destination group address to the P2MP LSP in the base router instance by configuring a static multicast group under a tunnel interface representing the P2MP LSP.
An FTN entry is programmed at the ingress of the head-end node that maps the FEC of a received user IP multicast packet to a list of outgoing interfaces (OIF) and corresponding NHLFEs.
The head-end node replicates the received IP multicast packet to each NHLFE. Replication is performed at ingress toward the fabric or at egress forwarding engine depending on the location of the OIF.
At ingress, the head-end node performs a PUSH operation on each of the replicated packets.