Cisco Systems 78-11741-02 manual Configuring Bidirectional PIM, Bidir-PIM Overview, IPC-471

Configuring Bidirectional PIM

This chapter describes how to configure the Bidirectional PIM (bidir-PIM) feature. Bidir-PIM is a variant of the Protocol Independent Multicast (PIM) suite of routing protocols for IP multicast and is an extension of the existing PIM sparse mode (PIM-SM) feature. Bidir-PIM resolves some limitations of PIM-SM for groups with a large number of sources.

Bidir-PIM is based on the draft-kouvelas-pim-bidir-new-00.txt Internet Engineering Task Force (IETF) protocol specification. This draft and other drafts referenced by it can be found at the following URL: ftp://ftpeng.cisco.com/ipmulticast/drafts.

For more information on PIM-SM, refer to the “Configuring IP Multicast Routing” chapter of the Cisco IOS IP Configuration Guide and the Cisco IOS IP Command Reference, Volume 3 of 3: Multicast.

For a complete description of the bidir-PIM commands used in this chapter, refer to the “IP Multicast Routing Commands” chapter of the Cisco IOS IP Command Reference, Volume 3 of 3: Multicast. To locate documentation of other commands that appear in this chapter, use the command reference master index, or search online.

To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the “Identifying Supported Platforms” section in the “Using Cisco IOS Software” chapter.

Bidir-PIM Overview

Bidir-PIM is a variant of the PIM suite of routing protocols for IP multicast. In PIM, packet traffic for a multicast group is routed according to the rules of the mode configured for that multicast group. The Cisco IOS implementation of PIM supports three modes for a multicast group:

•Bidirectional mode

•Dense mode

•Sparse mode

A router can simultaneously support all three modes or any combination of them for different multicast groups. In bidirectional mode, traffic is routed only along a bidirectional shared tree that is rooted at the rendezvous point (RP) for the group. In bidir-PIM, the IP address of the RP acts as the key to having all routers establish a loop-free spanning tree topology rooted in that IP address. This IP address need not be a router, but can be any unassigned IP address on a network that is reachable throughout the PIM domain. This technique is the preferred configuration method for establishing a redundant RP configuration for bidir-PIM.

Cisco IOS IP Configuration Guide

IPC-471