Multicast Stub Routing and IGMP Helper

This topic is to discuss the following lesson:

why do you use IP PIM dens-mode in R2 ?

I did it to keep the stub router configuration simple, it will just forward anything.

Hello René,
I need to route multicast traffic on a Catalyst 3560 Layer 3 switch. Connected to the Layer 3 switch is connected Layer 2 switch which are connected to an Apple TV and wireless access points. I need the apple tv can route multicast traffic between different vlans. On a switch running the IP base image. The IP base image contains only PIM stub routing.

Please excuse my English.

thank you very much

Hi Daniel,

The last time I worked with the Apple TV it was impossible to route between different VLANs because the Bonjour protocol uses a TTL of 1. Just to be sure, run Wireshark and check if it’s still the case.

If so…your only option is to have the Apple TV and the clients within the same VLAN.


A possible work around to this could be to unicast or broadcast the traffic and use a multicast helper to push the traffic to different layer 3 addresses.

Here is more info on how I implemented a broadcast to multicast solution, i had to do it both ways:


R2 router configure as stub and R3 router configure as RP.
configured filter-list on R3 as per the lesson. so pim neighbors down on R3 and pim neighbors up on R2 i am not getting this one. below screen sort for your reference.


Hello Gowthamraj

Building a PIM neighborship between two routers is not a mutual process. What I mean is, each direction creates its own neighbor relationship. It is possible to have R2 see R3 as a neighbor, but R2 not to see R2 as a neighbor. This is exactly what is taking place in this lab.

By implementing the ip pim neighbor-filter 1 command, R2 is being blocked from appearing in R3’s neighbor table, while R3 is not blocked from appearing as R2’s neighbor. So what you see is expected behaviour.

I hope this has been helpful!