IGMP (router to client communication)
IGMP testing commands - simulate multicast receiver
- ip igmp join-group - response icmp echo, process switching mpackets
- ip igmp static-group - not response icmp echo
PIM – Protocol Independent Multicast - Router to router communication
Sparse Mode or Dense modes - this ONLY affect the traffic SENDING OUT interface; an interface will always receive multicast traffic once enble either "ip pim XXX mode".
Sparse Mode process:
multicast server - [S,G] fisrt hop router - unicast - RP - [*,G] - last hop router - receiver
multicast server - [S,G] fisrt hop router - [S,G] - RP - [*,G] - last hop router - receiver
multicast server - [S,G] fisrt hop router - [S,G] - last hop router - receiver
Useful command:
ip igmp join-group multicast-address - simulate a join host
sh ip mr multicast-address - check [S,G] and [*,G]
sh ip mr count - check multicast traffic stats, look for failures such as rpf or oil-null
sh ip rpf source-ip-address
Reference: IPEXPERT
Basic Multicast Troubleshooting Tools
IP Multicast Troubleshooting Guide
IP Multicast Routing Commands
