Pim configuration, Pim overview, Introduction to pim-dm – H3C Technologies H3C SecPath F1000-E User Manual
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PIM Configuration
This chapter includes these sections:
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Configuring PIM Common Features
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Displaying and Maintaining PIM
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NOTE:
The term
router in this document refers to network routing devices running a routing protocol.
PIM Overview
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:
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Protocol Independent Multicast–Dense Mode (PIM-DM), and
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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: