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New Member

PIM dense mode flooding


pim dense mode flood every 3 minutes and prune to construct forwarding tree.

question is

1. what kind of traffic it floods and how much bandwidth it consumes.

since flooding happens in every 3 mnts i am scared to implement on the network.

i hope it won't flood multicast video stream from source server every 3mnts

Regards, Rajesh


Re: PIM dense mode flooding

Hello Rajesh,

Are you using CISCO with recent IOS?

PIM dense mode builds source-based multicast distribution trees that operate on a flood and prune principle. Multicast packets from a source are flooded to all areas of a PIM dense mode network. PIM routers that receive multicast packets and have no directly connected multicast group members or PIM neighbors send a prune message back up the source-based distribution tree toward the source of the packets. As a result, subsequent multicast packets are not flooded to pruned branches of the distribution tree. However, the pruned state in PIM dense mode times out approximately every 3 minutes and the entire PIM dense mode network is reflooded with multicast packets and prune messages. This reflooding of unwanted traffic throughout the PIM dense mode network consumes network bandwidth.

The PIM Dense Mode State Refresh feature keeps the pruned state in PIM dense mode from timing out by periodically forwarding a control message down the source-based distribution tree. The control message refreshes the prune state on the outgoing interfaces of each router in the distribution tree.""

so, if your routers are sending State Refresh messages, there's no need to worry.


if it does, please rate this post.


New Member

Re: PIM dense mode flooding

vlad ,

Thanks for the response, How can I check routers are sending state refresh messages?

it is running on msfc software Version 12.1(8a)E5.

Regards, Rajesh

Re: PIM dense mode flooding

You can check this messages with:

Router# debug ip pim

*Mar 1 00:25:10.416:PIM:Originating refresh message for


*Mar 1 00:25:10.416:PIM:Send SR on Ethernet1/1 for (,


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