! Useful commands on R4:

ip multicast-routing
ip pim rp-address 2.2.2.2

int range gig 1/0,gig2/0,fa4/1
ip pim sparse-mode

ping 224.67.8.3 source gig 2/0

Useful commands on all routers:

show ip mroute
show ip pim neighbor
show ip igmp interface