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Another way to get information about multicast routes is with the show multicast<br />

route command:<br />

aviva@RouterA> show multicast route<br />

Address family INET<br />

Group: 224.1.1.1<br />

Source: 10.0.15.1/32<br />

Upstream interface: fe-0/0/1.0<br />

Downstream interface list:<br />

se-0/0/3.0<br />

Address family INET6<br />

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

When a router receives multicast traffic, it places the (S,G) route information in the<br />

JUNOS multicast cache, inet.1. This recipe shows how to display the contents of<br />

this table with a variant of the show route command that displays just the inet.1 table.<br />

The output in this recipe shows one route, which is displayed as 224.1.1.1,10.0.15.1.<br />

The first part, 224.1.1.1, is the multicast group, and the second part is the source<br />

address of the route. Looking at the network topology, you see that 10.0.15.1 is the<br />

address of the fe-0/0/1 interface on RouterA, which connects to RouterE. This tells<br />

you that RouterA learned this route from a source connected to RouterE. The second<br />

column of the show route output reports that the route was learned from PIM,<br />

has a preference of 105 ([PIM/105]), and is a multicast route.<br />

The format of the show route output is optimized for unicast routes, and really<br />

doesn’t represent the details about multicast routes very well. A better command to<br />

use instead is show multicast route. The basic output is shown in this recipe. Use the<br />

extensive form to get more detailed information:<br />

aviva@RouterA> show multicast route extensive<br />

Address family INET<br />

Group: 224.1.1.1<br />

Source: 10.0.15.1/32<br />

Upstream interface: fe-0/0/1.0<br />

Downstream interface list:<br />

se-0/0/3.0<br />

Session description: ST Multicast Groups<br />

Statistics: 0 kBps, 0 pps, 5 packets<br />

Next-hop ID: 359<br />

Upstream protocol: PIM<br />

Route state: Active<br />

Forwarding state: Forwarding<br />

Cache lifetime/timeout: 356 seconds<br />

Wrong incoming interface notifications: 0<br />

The first several fields are common to the regular and detailed output. The Group<br />

field reports the multicast group that sent the route, which here is 224.1.1.1. The<br />

Source and Upstream interface lines tell that this route was learned from 10.0.15.1,<br />

which is the address of the fe-0/0/1 interface to RouterE. This interface is upstream,<br />

or toward the multicast source.<br />

600 | Chapter 16: IP Multicast<br />

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

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.

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