3Com Switch 8800 Advanced Software V5 Configuration Guide

540 CHAPTER 41: IGMP SNOOPING CONFIGURATION
Figure 169 Before and after IGMP Snooping is enabled on Layer 2 device
Basic Concepts in IGMP
Snooping
IGMP Snooping related ports
As shown in Figure 170, Router A connects to the multicast source, IGMP
Snooping runs on Switch A and Switch B, Host A and Host C are receiver hosts
(namely, multicast group members).
Figure 170 IGMP Snooping related ports
Ports involved in IGMP Snooping, as shown in Figure 170, are described as
follows:
■ Router port: A router port is a port on the Layer-3 multicast device or the IGMP
querier side of the Ethernet switch. In the figure, Ethernet 1/1/10 of Switch A
Multicast packet transmission
without IGMP Snooping
Source
Multicast router
Host A
Receiver
Host B
Host C
Receiver
Multicast packets
Layer 2 switch
Multicast packet transmission
when IGMP Snooping runs
Source
Multicast router
Host A
Receiver
Host B
Host C
Receiver
Layer 2 switch
Router A Switch A
Switch B
Eth1/1 /10 Eth1/1/1
Eth 1/1/2
Eth1 /1/10
Eth1/1 /1
Receive
r
Receiver
Host A
Host B
Host C
Host D
Source
Multicast packets
Router port
Member port