3Com Switch 4800G 24-Port Configuration Manual page 554

554 C 42: IGMP S
HAPTER
Basic Concepts in IGMP
Snooping
C
NOOPING ONFIGURATION
Figure 170 Before and after IGMP Snooping is enabled on the Layer 2 device
Multicast packet transmission
without IGMP Snooping
Source
Host A
Receiver
Host B
Multicast packets
IGMP Snooping related ports
As shown in Figure 171, 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 171 IGMP Snooping related ports
Router A
Eth1/0/1
Source
Router port
Member port
Multicast packets
Ports involved in IGMP Snooping, as shown in Figure 171, are described as
follows:
Router port: A router port is a port on the Ethernet switch that leads switch
■
towards the Layer 3 multicast device (DR or IGMP querier). In the figure,
Ethernet 1/0/1 of Switch A and Ethernet 1/0/1 of Switch B are router ports. The
Multicast router
Layer 2 switch
Host C
Receiver
Switch A
Eth1/0 /2
Eth 1/0/3
Receiver
Eth 1/0/1
Eth1/0 /2
Host C
Switch B
Host D
Multicast packet transmission
when IGMP Snooping runs
Multicast router
Source
Layer 2 switch
Host A
Receiver
Host B
Receiver
Host A
Host B
Host C
Receiver