IGMP

Overview

IGMP is a multicast protocol which service providers can use to establish multicast group memberships on a LAN. Within the LAN, end users use IGMP to communicate with a local multicast router, which then uses PIM to distribute the IGMP messages to other local and remote multicast routers. Multicast routers send regular membership queries to IGMP hosts which respond with membership reports. Multicast routers can use these reports to determine which hosts are interested in receiving particular multicast messages.

Configuring a group interface query source IP address on the IGMP site allows a VPLS IGMP snooping instance to register the port facing an ESM port as a multicast router port.

In a multi-chassis implementation on an NE configured with active/active MC-LAG, multicast IGMP traffic from an access network is forwarded to both multicast redirection interfaces. This would cause the downstream device to receive duplicate IGMP messages. The Redundant Multicast option allows you to identify a single IGMP interface as the designated forwarder to the redirection interface, ensuring that the downstream device only receives the IGMP traffic once.

IGMP operates above the network layer on IPv4 networks.