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Multicast Routing Issues

I'm currently having issues sending multicast across a GRE tunnel. I attached a crude drawing to kinda of help depict what I'm talking about...Here is a quick run down of what we are seeing..

- both routers have the correct pim neighborship

- multicast traffic originating from the network is being transmitted over to the network. We verified this with show ip mroute active on both routers. We can also see it in show ip mroute The problem is the clients on the 172 network don't actually recieve the multicast.

- multicast traffic originating from the 172 network is not being routed over to the 192 network. We dont see any active mroutes on either routers. We do see the traffic being originated, and the router on the 172 network recieving the multicast, but it drops the packets. We see this in the sho ip mroute count. The results show all packets being dropped by "other" reasons (OIF-null, rate-limit. etc.). Also, when debugging the ip mroute we can see that the packets are being routed to the "null" route list.

- lastly, the router on the 192 network shows mroutes from the 172 network as incoming on the physical interface (e.g. G1/0) not the GRE tunnel. The router on the 172 network does show the mroutes incoming on the GRE.

I don't have access to the debug logs to post them but that's pretty much it. If there is any more information I can provide please let me know.


Cisco Employee

Re: Multicast Routing Issues


I would like to know the multicast group is in dense mode or in sparse mode? if it is sparse, where is RP? Where are the multicast source and multicast receiver in your picture?

Would be great if you can provide the show run and show ip mroute from the multicast routers on the path.


Lei Tian

Re: Multicast Routing Issues

i agree that you need an RP the ip sparse dense mean you will not need auto RP to be configured

but you stil need an RP to be configured

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