Huawei Quidway S9300

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4.1 Introduction to PIM-SM

This section describes the basic information about PIM-SM.

PIM indicates that a static route or any unicast routing protocol such as RIP, OSPF, IS-IS, or

BGP can provide routing information for IP multicast. Although the multicast routing entry is

generated through the unicast routing table, the multicast routing is independent of unicast

routing protocols.

NOTE

The switch referred in the following contents is an S9300 supporting the Layer 3 multicast protocol and

multicast routing function.

PIM forwards multicast packets through the RPF mechanism. The RPF mechanism uses the

existing unicast routing information to create a multicast forwarding tree. When a multicast

packet reaches an S9300, the S9300 performs the RPF check. If the RPF check is passed, the

S9300 creates the mapping multicast routing entry and forwards the multicast packet. The the

multicast packet fails to pass the RPF check, the S9300 discards the packet.

PIM-SM belongs to a multicast routing protocol in sparse mode. PIM-SM performs the following

operations: neighbor discovering, asserting, DR election, rendezvous point (RP) discovering,

joining, pruning, registering, and SPT switchover.

As shown in Figure 4-1, PIM-SM is applicable to a large-scale network with sparsely-distributed

members.

Figure 4-1 Application of PIM-SM in a multicast network

Source

Multicast

UserB

UserC

Receiver

IGMP

PIM-SM

IGMP

Receiver

UserA

PIM-SM

By using PIM-SM, you can construct two multicast models: ASM and SSM.

Quidway S9300 Terabit Routing Switch

Configuration Guide - Multicast 4 PIM-SM Configuration

Issue 01 (2009-07-28) Huawei Proprietary and Confidential

4-3

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