7210 SAS routers use IGMP to manage membership for a specific multicast session. IGMP is not enabled by default. The IGMP context is not operational until at least one IGMP interface is specified in the context, at which time the interface is enabled for IGMP.
Traffic can only flow away from the router to an IGMP interface, and to and from a PIM interface. A router directly connected to a source must have PIM enabled on the interface to that source. In a network, traffic travels from PIM interface to PIM interface, and arrives on an IGMP-enabled interface.
The IGMP CLI context allows you to specify an existing IP interface, and modify the interface-specific parameters. Static IGMP group memberships can be configured to test multicast forwarding without a receiver host. When IGMP static group membership is enabled, data is forwarded to an interface without receiving membership reports from host members.
When static IGMP group entries on point-to-point links that connect routers to a rendezvous point (RP) are configured, the static IGMP group entries do not generate join messages toward the RP. When a host needs to receive multicast sessions, it sends a join message for each multicast group it needs to join. Then, a leave message may be sent for each multicast group it no longer wants to participate with.
A multicast router keeps a list of multicast group memberships for each attached network, and an interval timer for each membership. Hosts issue a Multicast Group Membership Report when they want to receive a multicast session. The reports are sent to all multicast routers.
PIM is not enabled by default. Because it is an interface function, PIM is not operational until at least one interface is specified in the PIM context, at which time the interface is enabled for PIM. When PIM is enabled, data is forwarded to network segments with active receivers that have explicitly requested the multicast group.