H3C Technologies H3C S12500 Series Switches - Manual (Page 61)

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Configuring PIM snooping
Overview
Protocol Independent Multicast (PIM) snooping runs on Layer 2 devices. It determines 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 that multicast data can be forwarded to only the ports that are interested
in the data.
Figure 18 Multicast packet transmission without or with PIM snooping
As shown in Figure 18 , 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-capable routers are in the same VLAN.
• When running IGMP snooping without PIM snooping, the Layer 2 switch maintains the router ports
according to PIM hello messages received from PIM-capable routers, broadcasts all other types of
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