In this post let’s detail the operation of PIM (Protocol Independent Multicast) in sparse mode. Previous posts tackled the operation of PIM dense mode. Let’s recall that PIM is the multicast routing protocol that allows PIM routers exchange information needed distribute multicast traffic to receivers.
Introduction
This blog is a part of a serie of blogs about multicast routing:
- Multicast routing: a step by step
- Multicast routing: PIM dense
- Multicast routing: From the source
- Multicast routing: Hold ASM for a moment
- Multicast routing: Rather than dense, sparse it and let’s meet at rendez-vous point
- Multicast routing: RPF
Lab setup
Instead of use PIM-Dense (flood and prune), seen in the previous post of this serie on Multicast operatoin, we use PIM-Sparse to build the forwarding path from the server to the client.
PIM-Sparse
PIM-Sparse is enabled on R1, R2, R3 and R4 routers
RIP for unicast routing (and RPF)
We use RIP for unicast routing and multicast a ping from the source for test purpose toward the group of receivers
IGMP
At R1 we check first that Client1 is registered to the group which is the case
The interface of router R1 facing Client1 is configured for PIM-Sparse
Enable PIM in sparse mode
The details of this PIM interface are given in the following figure. We can check that PIMv2 is enable at interface level in sparse mode, that the RP or Rendez-vous point for this mode is the router itself (R1). We have also counters for PIM neighbors, in/out multicast packets. We check also that multicast switching is fast (at hardware level) and not process switched (at CPU level).
