Users Guide

Table 72. PIM terminology (continued)
Terminology Definition
Shortest path tree (SPT) The root node of the SPT is the multicast source. The multicast traffic routes to the
receiver on the shortest path. This setup reduces network latency and traffic
congestion at the RP.
Outgoing interface (OIF) The OIF is the interface through which a multicast packet is sent out towards the
receiver.
Incoming interface (IIF) The IIF is the interface through which a multicast packet is received towards the
source or the RP.
Reverse path forwarding (RPF) The RPF is the path the router uses to reach the RP or the multicast source.
Standards compliance
OS10 complies to the following standards:
● RFC 4601 for PIM-SM
● RFC 3569 for PIM-SSM
PIM-SM
PIM sparse mode (PIM-SM) is a multicast routing protocol for networks with receivers that are sparsely distributed. Receivers
have to explicitly send a join message to join particular groups or sources. PIM join and prune messages are used to join and
leave multicast distribution trees.
PIM-SM uses shared trees with the root node being the rendezvous point (RP). All multicast sources use the RP to route the
traffic to the receiver. The last hop router (LHR) sends an (*,G) join message towards the RP. The designated router
connected to the first hop router (FHR) encapsulates multicast data that comes from the multicast source in PIM control
messages and sends it via unicast to the RP as PIM register messages. The RP sends an (S, G) join towards the source. When
the RP receives native data traffic from the source, it sends a register stop message to the FHR.
OS10 supports static and dynamic configuration of an RP address for a multicast group.
To keep the PIM-SM state alive, all PIM neighbors send periodic hello messages.
You must enable PIM-SM on each of the participating interfaces. Be sure to have multicast routing enabled on the system. To
do this, use the ip multicast-routing command from CONFIGURATION mode.
OS10# configure terminal
OS10(config)# interface vlan 100
OS10(conf-if-vl-100)# ip pim sparse-mode
PIM-SM sample configuration
This section describes how to enable PIM-SM in the FHR, RP, and LHR nodes using the topology show in the following figure.
To enable PIM-SM, perform the following configurations on each of the nodes (FHR, RP, and LHR):
1. Enable multicast routing globally in CONFIGURATION mode.
ip multicast-routing
2. Enable PIM-SM on the required Layer 3 interfaces of the nodes in INTERFACE mode.
ip pim sparse-mode
3. Configure an RP address on every multicast-enabled node in CONFIGURATION mode.
ip pim rp-address
1052
Multicast