Protocol Independent Multicast (PIM) provides IP multicast forwarding by leveraging static routes or
unicast routing tables generated by any unicast routing protocol, such as routing information protocol

(RIP), open shortest path first (OSPF), intermediate system to intermediate system (IS-IS), or border

gateway protocol (BGP). Independent of the unicast routing protocols running on the device, multicast

routing can be implemented as long as the corresponding multicast routing entries are created through

unicast routes. PIM uses the reverse path forwarding (RPF) mechanism to implement multicast forwarding.

When a multicast packet arrives on an interface of the device, it is subject to an RPF check. If the RPF
check succeeds, the device creates the corresponding routing entry and forwards the packet; if the RPF

check fails, the device discards the packet. For more information about RPF, see Multicast Routing and

Forwarding Configuration in the IP Multicast Volume.
Based on the implementation mechanism, PIM falls into two modes:

•

Protocol Independent Multicast–Dense Mode (PIM-DM), and

•

Protocol Independent Multicast–Sparse Mode (PIM-SM).

NOTE:

To facilitate description, a network comprising PIM-capable routers is referred to as a “PIM
domain” in this document.

Introduction to PIM-DM

PIM-DM is a type of dense mode multicast protocol. It uses the “push mode” for multicast forwarding, and

is suitable for small-sized networks with densely distributed multicast members.
The basic implementation of PIM-DM is as follows:

This manual is related to the following products:

H3C SecPath F5000-A5 Firewall H3C SecBlade FW Cards H3C SecPath U200-A U200-M U200-S