When local IGMP join command for a group is configured on the uplink of a tier-0 service router (SR), IGMP group is joined on the uplink interface on the Edge Linux.
The designated router (DR) on the uplink VLAN interface will issue a PIM (*,g) join towards the Rendezvous Point (RP) upon receiving an IGMP report for the group g.
Traffic flow:
- IGMP join is configured on the uplink of the non-active multicast node of the tier-0 SR and multicast traffic is forwarded to the non-active node from the RP. Since north-south traffic on non-active multicast node is not processed regardless of it is DR or non-DR for the uplink interface, the packet will be dropped on the non-active node. (s,g) mroute will not be present.
- IGMP join is configured on the uplink of the active multicast node of the tier-0 SR and multicast traffic is forwarded to the active node from the RP.
- If the node is non-DR for the uplink interface, the traffic will be dropped.
- If the node is DR for the uplink interface:
- If IGMP join is given on the uplink interface which is also the interface to reach Source, then the incoming interface will be same as the outgoing interface for the (s,g) and the mroute will not be installed.
- If IGMP join is given on the uplink interface which is different from the incoming interface for a given (s,g) then the (s,g) mroute will be installed.
