Basic Concepts In Igmp Snooping - 3Com S7906E Configuration Manual

Figure 1-1 Before and after IGMP snooping is enabled on the Layer 2 device
Multicast packet transmission
without IGMP Snooping
Source
Host A
Receiver
Multicast packets
IGMP snooping forwards multicast data to only the receivers requiring it at Layer 2. It brings the
following advantages:
Reducing Layer 2 broadcast packets, thus saving network bandwidth.
Enhancing the security of multicast traffic.
Facilitating the implementation of per-host accounting.

Basic Concepts in IGMP Snooping

IGMP Snooping related ports
As shown in Figure
and Switch B, and Host A and Host C are receiver hosts (namely, multicast group members).
Figure 1-2 IGMP snooping related ports
Router A
Source
Router port
Member port
Multicast packets
Ports involved in IGMP snooping, as shown in
Multicast router
Layer 2 switch
Host C
Receiver
Host B
1-2, Router A connects to the multicast source, IGMP snooping runs on Switch A
Switch A
GE2/0/1 GE2/0/2
GE2/0/3
GE2/0/1
GE2/0/2
Switch B
Multicast packet transmission
when IGMP Snooping runs
Source
Host A
Receiver
Host B
Receiver
Host A
Host B
Receiver
Host C
Host D
Figure 1-2, are described as follows:
1-2
Multicast router
Layer 2 switch
Host C
Receiver