To forward multicast packets over a P2MP LSP, perform the following steps:
Create a tunnel interface associated with the P2MP LSP: config>router>tunnel-interface rsvp-p2mp lsp-name. (The config>router>pim>tunnel-interface command has been discontinued.)
Add static multicast group joins to the PIM interface, either as a specific <S,G> or as a <*,G>: config>router>igmp>tunnel-if>static>group>source ip-address and config>router>igmp>tunnel-if>static>group>starg.
The tunnel interface identifier consists of a string of characters representing the LSP name for the RSVP P2MP LSP. Note that MPLS actually passes to PIM a more structured tunnel interface identifier. The structure follows the one BGP uses to distribute the PMSI tunnel information in BGP multicast VPN as specified in draft-ietf-l3vpn-2547bis-mcast-bgp, Multicast in MPLS/BGP IP VPNs. The format is: <extended tunnel ID, reserved, tunnel ID, P2MP ID> as encoded in the RSVP-TE P2MP LSP session_attribute object in RFC 4875.
The user can create one or more tunnel interfaces in PIM and associate each to a different RSVP P2MP LSP. The user can then assign static multicast group joins to each tunnel interface. Note however that a specific <*,G> or <S,G> can only be associated with a single tunnel interface.
A multicast packet which is received on an interface and which succeeds the RPF check for the source address is replicated and forwarded to all OIFs which correspond to the branches of the P2MP LSP. The packet is sent on each OIF with the label stack indicated in the NHLFE of this OIF. The packets are also replicated and forwarded natively on all OIFs which have received IGMP or PIM joins for this <S,G>.
The multicast packet can be received over a PIM or IGMP interface which can be an IES interface, a spoke SDP-terminated IES interface, or a network interface.
To duplicate a packet for a multicast group over the OIF of both P2MP LSP branches and the regular PIM or IGMP interfaces, the tap mask for the P2MP LSP and that of the PIM based interfaces needs to be combined into a superset MCID.