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multicast issue

I'm setting up multicast in my network.

I've got 2 routers candidates rp for 2 different ranges of IPs


ip pim send-rp-announce scope 16 group-list 99

access-list 99 permit



Router(config)#ip pim send-rp-announce scope 16 group-list 99

Router(config)#access-list 99 permit


plus a R3 is in charge with the mapping between groups and mapping agents

Router(config)#ip pim send-rp-discovery scope 16


Everything's cool, even if I type

Router#show ip pim rp mapping


RP (?), v2v1

Info source: (?), elected via Auto-RP

Uptime: 01:46:09, expires: 00:02:45


RP (?), v2v1

Info source: (?), elected via Auto-RP

Uptime: 00:32:08, expires: 00:02:51

All the routers (including loopbacks) are set with

ip pim sparse-mode

+ they all have the

ip pim autorp listener

to make autorp working over sparse-mode

Everything seems to be ok.

I've joined group and from a 4th router.

Pinging from different devices in the network works in some areas (in other not), where not at all :-(

Can anybody shed light for me on the way to troubleshoot this issue?

Thanks a lot!


Re: multicast issue

Hello bellocarico,

Did you check for RPF issues? Take a look at the group members that did not respond to your echo request. View the mroute table if downstream interfaces are being pruned, modify your tree or create a tunnel to mitigate the problem.

If you need further help, please provide a simple diagram of your multicast topology.



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New Member

Re: multicast issue

Pl. do debug with this command for each group and see mroute established, rpf passing and neighbour is there outside that area.

show ip mroute

show ip rpf

show ip pim neighbor

New Member

Re: multicast issue

Topology in attachment RP is R2 publishing it as the loopback0, SW2 is the mapping agent ( still on loopback 0)

On R3 eth0 I've set an ip igmp join-group

When I try to ping from R4 it fails and this is the output of the show ip mroute (still on R4)

(*,, 00:00:04/stopped, RP, flags: SPF

Incoming interface: Serial0/3, RPF nbr, Mroute

Outgoing interface list: Null

Where R5 says: Group not found

But if I ping from R5 sirectly, it works...

Note, 141,1,145,4 is not an ethernet connection like the topology says, but a serial connection instead (serial0/3)

I'm reading this document right now

These are the things I'm confused on:

- Is the ip igmp join-group simulating a source or destination? (I guess destination)

- Is the ping simulating a source or destination (I guess a source)

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