By Beau Williamson
This chapter appears in the book Developing IP Multicast Networks, Volume I by Cisco Press (ISBN 1-57870-077-9).
For a review of multicast, see Appendix I, "Overview of IP Multicast."
Protocol Independent Multicast sparse mode (PIM-SM), like PIM dense mode (PIM-DM), uses the unicast routing table to perform the Reverse Path Forwarding (RPF) check function instead of maintaining a separate multicast route table. Therefore, regardless of which unicast routing protocol(s) is (are) used to populate the unicast routing table (including static routes), PIM-SM uses this information to perform multicast forwarding; hence, it too is protocol independent.
Some key characteristics of PIM-SM are
Protocol independent ...