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You administratively configure the RPs in your domain, and one RP is active at a<br />

time. (Specifically, one RP per multicast group is active at one time in the case that<br />

some RPs do not service all groups.)<br />

DVMRP and PIM are both multicast routing protocols, using RPF to forward multicast<br />

traffic. A number of other protocols support functions required by DVMRP and<br />

PIM, but they are not routing protocols because they do not handle forwarding state<br />

information. The Multicast Source Discover Protocol (MSDP) expands PIM-SM to<br />

allow RPs in different autonomous systems to learn about active multicast sources in<br />

other ASs. Effectively, MSDP makes it possible for multicast applications to run<br />

across the global Internet. Also, BGP has been extended with Multiprotocol BGP<br />

(MBGP; see RFC 2858) so that BGP carries NLRIs that can be used by other protocols,<br />

including multicast. MBGP allows a multicast router to create two separate<br />

routing tables, one that is used to make unicast routing decisions and a second to<br />

make RPF decisions.<br />

For more information about multicast, see Interdomain Multicast Routers: Practical<br />

Juniper Networks and Cisco Systems Solutions (Addison-Wesley).<br />

16.1 Configuring PIM-SM<br />

Problem<br />

You want to configure the router to support multicast within your AS.<br />

Solution<br />

Turn on PIM-SM on the router’s interfaces:<br />

[edit protocols pim]<br />

aviva@RouterA# set interface all<br />

Disable PIM on the router’s out-of-band management interface. On J-series routers,<br />

disable PIM on the fe-0/0/0 interface:<br />

[edit protocols pim]<br />

aviva@RouterA# set interface fe-0/0/0.0 disable<br />

On M-series and T-series routers, disable it on fxp0:<br />

[edit protocols pim]<br />

aviva@R1# set interface fxp0.0 disable<br />

When you turn on PIM-SM, the JUNOS software automatically enables IGMP Version<br />

2 on all LAN interfaces.<br />

<strong>Discussion</strong><br />

Setting up PIM-SM on the router is very straightforward. In the PIM protocol configuration,<br />

specify the interfaces on which you want PIM to run. If you want the router<br />

This is the Title of the Book, eMatter Edition<br />

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.<br />

Configuring PIM-SM | 579

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