9.6 Optional IP Multicast Routing Tasks
9.6.3
Join a multicast group
Cisco routers can be configured to be members of a multicast group. Being a member of a multicast group is useful in determining multicast reachability in a network. If a router is configured to be a member of a specific multicast group, that router can respond to commands, such as ping and Internet Control Message Protocol (ICMP) echo requests, addressed to that group. A group member router can also participate in multicast Cisco IOS traceroute actions.

To have the router join a multicast group, enter the following command in interface configuration mode.

Router(config-if)#ip igmp join-group group-address

Where group-address is the address of the multicast group.

The configuration example in Figure places the router in multicast Group 224.1.1.1.

By issuing a ping command specifying that multicast group address, you will cause all routers in that group to respond.

To cancel the membership of a router in a multicast group, enter the no ip igmp join-group group-address command.

Note: The term interface describes the primary interface on an attached network. If a router has multiple physical interfaces on a single network, this protocol needs to run on only one of the interfaces. Hosts, on the other hand, need to perform their actions on all interfaces that have memberships associated with them.