IP Multicast

Unanswered Question
Feb 4th, 2007

i have a point to point leased line of 2 mbps connected with 2503 at both ends. i have a video streaming server which send multicast at and i want to receive it at the other end. how do enable the routers to do that.

Attached is a brief network diagram

Swapnil Jain

I have this problem too.
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Harold Ritter Sun, 02/04/2007 - 12:11

You need to enable PIM (preferably sparse-mode) on all router interfaces between the IP multicast source and receiver(s).

If you use pim sparse-mode, you need to configure a Rendez-vous Point (RP).

For more information on IP multicast and how to configure an RP, please refer to the following document:



Multicast Quick Start Configuration Guide:


Hope this helps,

dknov Sun, 02/04/2007 - 23:16


I won't go into the whole Multicast theory, but in essense the EASIEST way to make it work is just to enable "ip pim sparse-dense-mode" command on all relevant interfaces (internal/external on 2503s).

By far, not the most efficient method, but it will get you going.


swapniljain Tue, 02/06/2007 - 22:37


thanks for ur reply,

how do make the router to join the multicast group


dknov Wed, 02/07/2007 - 10:14


If your multicast receivers (clients) are not capable of generating IGMP Membershit Report (asa IGMP Join) messages or there are no clients at all, you can use "ip igmp join-group" command to get multicast traffic forwarded to the router. This command should be applied to the LAN interface of the router in question.

If you use spare-mode it will cause the router to generate (*,G) PIM Join messages towards the RP.

Other alternative is to use "ip igmp static-group" command, which in essense does the same, but your multicast traffic will be fast switched (and not process switched) and you will not be able to ping the group address (with igmp join-group command you will).




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