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

Flags: sparse<br />

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

Upstream neighbor: 10.0.15.1<br />

Upstream State: Local Source, Local RP<br />

Keepalive timeout: 116<br />

Downstream Neighbors:<br />

Interface: se-0/0/3.0<br />

10.0.16.2 State: Join Flags: S Timeout: 165<br />

When a host connected to a PIM router informs the router that it wants to receive<br />

traffic from a multicast group, the PIM router sends (S,G) Join messages out its RPF<br />

interfaces to inform the next upstream router that it wants to receive packets for that<br />

group. Each upstream router repeats this process until this branch of the multicast<br />

tree reaches the router directly connected to the multicast source or reaches a router<br />

that already has multicast forwarding state for the (S,G) pair.<br />

The show pim join command lists all groups the router has sent Join messages to and<br />

has successfully joined. The output in this recipe indicates that RouterA has joined<br />

six multicast groups. For each group, you see the multicast source of the group. This<br />

is either the IP address of a source router or an asterisk (*) if the Join message is<br />

directed toward any source. The RP line shows the address of the rendezvous point<br />

for the group, and Upstream interface is the router’s interface toward the group’s<br />

source.<br />

The extensive version of the command shows the upstream state, which is information<br />

about the upstream router, and downstream interfaces toward the multicast<br />

receiver.<br />

The output of the show pim join extensive command for group 224.1.1.1 agrees with<br />

the route information displayed with the show multicast route extensive command<br />

(explained in Recipe 16.9):<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 />

Checking the Groups for Which a PIM-SM Router Maintains Join State | 603<br />

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

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

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