Objectives
The simulator ticks each one as soon as the network meets it.
Run multicast routing-enable on R1, R2 and R3, and pim sm on every addressed interface (R2’s LoopBack0 too).
In the pim view of every router configure static-rp 2.2.2.2.
Enable igmp on R3 GigabitEthernet0/0/1 and join 239.1.1.1 on PC3.
From SRC ping 239.1.1.1: PC3 replies.
On R3, display pim routing-table shows (*, 239.1.1.1) with RP 2.2.2.2 and an (S, G) entry flagged SPT.
Before you start
VRP keeps RP settings in a separate pim view (enter it with pim). A router with PIM-SM but no RP for a group cannot build the shared tree, so every router needs the same static-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
The RPF check: multicast follows unicast routes backwards
A router accepts a multicast packet only on the interface it would use to reach the packet’s source (reverse path forwarding), and sends joins out of that same interface toward the RP or source. The unicast routing table decides the path, so a missing route or a link without PIM breaks multicast even when ping works.
