Cisco Support Community
Community Member

Question on PIM Auto-RP and Mapping Agents

Hi Experts,

I have a few basic questions about PIM Auto-RP mechanism.

Please correct my understanding about these below :

Question 1 -

A router, when configured with the command 'ip pim send-rp-announce loopback0 scope 16' announces itself as RP on the multicast address And, the Mapping Agent listens to these messages on and sorts them as (RP,Groups) and re-announces them on

Question 2 -

We know that RP is basically a mechanism for the sparse PIM mode wherein the routers get access to the multicast tree by reaching the RP router. If that is the case, then how do the routers actually get to know about the Auto-RP multicast group, in order for it to reach the actual RP for the actual multicast group it needs to join ?

Does it mean that the groups and always works in Dense mode fashion that it reaches all routers and is not pruned (as all routers need to disseminate the Auto-RP discovery information .. ?

Question 3 -

I am thinking of trying a multicast configuration on the routers using static-groups and join-group commands.. Would you know of some real nice useful links that have sample multicast lab examples ?

I know there will be a lot of great replies :-)



Community Member

Re: Question on PIM Auto-RP and Mapping Agents

Are my questions absurd or is something totally wrong with my post that there has not been a single reply even ?



Re: Question on PIM Auto-RP and Mapping Agents

A1) Yes thats correct announcement on .39 and discovery on .40

A2) For auto-RP to work sparse-dense mode has to be configured. Announcement and discovery happens in dense fashion and when S,G mapping are available it goes the sparse way.There are workarounds to make it work with sparse only, but its better to skip that when deploying in a live environment.

A3) You may not find anything on a link for Multicast Lab as such, but you can try to setup 5 to 8 routers to have a meaningful experimentation with multicast where you can designate 1 end always as source and 1 end as receiver and then play with the core using sparse, dense and sparse-dense, using single RP, multiple RP's.



CreatePlease to create content