R3303-HP HSR6800 Routers IP Multicast Configuration Guide

20
Configuring PIM snooping
Overview
PIM snooping is a multicast constraining mechanism operating at Layer 2. It examines which
ports are interested in multicast data by analyzing the received PIM messages, and adds the ports to a
multicast forwarding entry to make sure multicast data can be forwarded to only the ports that are
interested in the data.
Figure 107 Multicast packet transmission without or with PIM snooping
As shown in Figure 107, Source 1 sends multicast data to multicast group G1, and Source 2 sends
multicast data to multicast group G2. Receiver 1 belongs to G1, and Receiver 2 belongs to G2. The Layer
2 switch's interfaces that connect to the PIM routers are in the same VLAN.
• When the Layer 2 switch only runs IGMP snooping, it does the following actions:
Multicast packet transmission
when only IGMP snooping runs
Multicast packet transmission when
IGMP snooping and PIM snooping both run
Source 1
Source 2
Receiver 1 Receiver 2
Multicast packets (S1, G1) Join message (S1, G1)
Layer 2 switch
Source 1 Source 2
Receiver 1 Receiver 2
Layer 2 switch
Multicast packets (S2, G2) Join message (S2, G2)
PIM
router 3
PIM
router 1
PIM
router 2
PIM
router 4
PIM
router 3
PIM
router 1
PIM
router 2
PIM
router 4