1-2z Reducing Layer 2 broadcast packets, thus saving network bandwidth.z Enhancing the security of multicast traffic.z Facilitating the implementation of per-host accounting.Basic Concepts in IGMP SnoopingIGMP Snooping related portsAs shown in Figure 1-2, Router A connects to the multicast source, IGMP Snooping runs on Switch Aand Switch B, and Host A and Host C are receiver hosts (namely, multicast group members).Figure 1-2 IGMP Snooping related portsRouter A Switch ASwitch BGE1/0/1 GE1/0/2GE1/0/3GE1/0/1GE1/0/2ReceiverReceiverHost AHost BHost CHost DSourceMulticast packetsRouter portMember portPorts involved in IGMP Snooping, as shown in Figure 1-2, are described as follows:z Router port: A router port is a port on an Ethernet switch that leads the switch towards a Layer 3multicast device (DR or IGMP querier). In the figure, GigabitGigabitEthernet 1/0/0/1 of Switch Aand GigabitGigabitEthernet 1/0/0/1 of Switch B are router ports. The switch registers all its localrouter ports in its router port list.z Member port: A member port is a port on an Ethernet switch that leads the switch towards multicastgroup members. In the figure, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A andGigabitEthernet 1/0/2 of Switch B are member ports. The switch registers all the member ports onthe local device in its IGMP Snooping forwarding table.
