At an LSR node that is a branch node, the LSR performs a replication and a label swapping for each leaf of the P2MP LSP. An ILM entry is programmed at the ingress of the LSR to map an incoming label to a list of OIF and corresponding NHLFEs. There is a limit of 127 OIF/NHLFEs per ILM entry.
The following is an exception handling procedure for control packets received on an ILM in a branch LSR, packets that arrive with the TTL in the outer label expiring are sent to the CPM for further processing and not copied to the LSP branches.