- Foundry Router User Guide

Chapter 14

Multicasting

Multicasting Overview

Traditional multicast routing mechanisms such as Distance Vector Multicast Routing Protocol (DVMRP) and

Multicast Open Shortest Path First (MOSPF) were intended for use within regions where groups are densely

populated or bandwidth is universally plentiful. When groups, and senders to these groups, are distributed

sparsely across a wide area, these “dense mode” schemes do not perform efficiently.

Protocol Independent Multicast (PIM)

Protocol Independent Multicast (PIM) protocols route multicast packets to multicast groups. PIM is protocol

independent because it can leverage whichever unicast routing protocol is used to populate unicast routing table.

There are two modes of PIM protocol – Dense mode (DM) and Sparse mode (SM). Foundry supports SM only.

PIM-DM floods multicast traffic throughout the network initially and then generates prune messages as required.

PIM-SM attempts to send multicast data only to networks which have active receivers. This is achieved by having

a common Rendezvous Point (RP) known to the senders and receivers and by forming shared trees from the RP

to the receivers.

PIM-SM is described in RFC 2362.

PIM Commands

The general PIM commands supported in this release are:

ABLE 4 PIM COMMANDS

Global parameters

Enable PIM Foundry/configure/ip# pim

Configure PIM mode Foundry/configure/ip/pim# mode [sparse | dense]

Configure Assert

Holdtime

Foundry/configure/ip/pim#assert-holdtime <time#

Configure Hello Interval Foundry/configure/ip/pim#hello-interval <time#

Configure Hello Holdtime Foundry/configure/ip/pim#hello-holdtime <time#

Configure Hello priority Foundry/configure/ip/pim#hello-priority <value#