15.4.1 IPv4 Multicast Routing Protocol Overview

Multicast routing protocols are used for path control. The Switch supports the multicast routing protocols listed below.

• PIM-SM (Protocol Independent Multicast-Sparse Mode)

  This protocol uses the unicast IPv4 path structure to perform multicast path control. After packets have been sent to the rendezvous point, communication is performed on the shortest path.

• PIM-SSM (Protocol Independent Multicast-Source Specific Multicast)

  PIM-SSM is extended PIM-SM functionality. that communicates on the shortest path without using a rendezvous point.

The following table describes appropriate networks for multicast protocols.

Table 15-8: Adaptation modes for multicast routing protocols

Multicast Protocol	Appropriate networks
PIM-SM	Networks on which multicast group members are sparsely distributed
PIM-SSM

PIM-SM and PIM-SSM can operate simultaneously. but cannot use the same group. Also, if routers running PIM-SM, routers running PIM-DM, and routers running DVMRP exist on the same network, multicast packets are not forwarded between each router. To forward multicast packets within the same network, set the same multicast protocol for all routers. For the adaptation modes of each protocol, see also section 15.5.3, "Example of Adapted Network Configuration."