Cisco LAN Switching Fundamentals

Summary

This chapter illustrated the intricacies involved with IGMP snooping and CGMP. IGMP snooping is enabled by default on Catalyst 6000 switches. CGMP is the default for the Catalyst 5000 family. Unlike IGMP snooping, CGMP requires configuration changes on the router. Via the IGMP snooping feature, the switch is able to listen to the conversation between the router and the host machine. Hence, rather than flooding the VLAN with multicast traffic, the switch forwards the traffic to hosts that explicitly requested the stream. CGMP forwards the IGMP messages to the router, which converts the IGMP packet into a CGMP packet and forwards it back to the switch. Despite CGMP local leave implementation, where the CGMP-enabled switch can intercept ...