Objectives
The simulator ticks each one as soon as the network meets it.
Enable ip multicast-routing and ip pim sparse-mode on every addressed interface of R1–R4 (including R2’s Loopback0).
On every router configure ip pim rp-address 2.2.2.2.
Join 239.1.1.1 on PC3 and on PC4.
From SRC ping 239.1.1.1: PC3 and PC4 both reply.
On R3, show ip mroute: (*,G) points at RP 2.2.2.2 with the J flag, and the (S,G) entry has the T flag (SPT switchover).
Before you start
Receivers’ routers send (*,G) joins toward the RP, building the shared tree. The source’s first-hop router registers the stream to the RP, the RP joins the source, and once the first packet arrives the last-hop router joins the source directly (SPT switchover, Cisco’s default threshold of 0). Every router must agree on the RP.
Concept
PIM sparse mode (ASM): shared tree, register, SPT
Sparse mode sends a stream only where it is requested. Receivers’ routers join a shared tree rooted at a rendezvous point (RP); the source’s router registers the stream to the RP; once the stream arrives, the receiver’s router joins the source directly on the shortest-path tree (SPT).
Concept
IGMP: how a receiver asks for a group
A multicast group (224.0.0.0/4) is an address many receivers can listen to at once. A host tells its local router it wants a group with an IGMP membership report; the router then pulls the stream toward that LAN. IGMPv2 can only name the group; IGMPv3 can also name the source.
