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PIM CONFIGURATION
When configuring PIM, go to these sections for information you are interested in:
■ “PIM Overview” on page 629
■ “Configuring PIM-DM” on page 641
■ “Configuring PIM-SM” on page 643
■ “Configuring PIM-SSM” on page 652
■ “Configuring PIM Common Information” on page 653
■ “Displaying and Maintaining PIM” on page 658
■ “PIM Configuration Examples” on page 659
■ “Troubleshooting PIM Configuration” on page 669
n
The term “router” in this document refers to a router in a generic sense or a Layer
3 switch running the PIM 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.
Based on the routing mechanism, PIM falls into two modes:
■ Protocol Independent Multicast-Dense Mode (PIM-DM), and
■ Protocol Independent Multicast-Sparse Mode (PIM-SM).
n
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:
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