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PIM Joins not switching through catalyst 3560G


I have the network described below, on which I am running PIM.

(network) ---- Embedded Linux Router --(vlan 5)-- CAT 3560G --(vlan 5)-- Cisco 1811 Router ---- Multicast Listener

The Linux Router and the 1811 have formed a PIM neighbor relationship. 

The multicast listener sends an IGMP Join and I can see the PIM join leave the 1811 router (via "debug ip pim").

Using tcpdump on my linux router I never see the Join come in, but I can see the PIM Hellos (which is why the neighbor relationship formed).

Does anyone know what might be going on here?  Any help would be appreciated.



PIM Joins not switching through catalyst 3560G

Hi There,

PIM is a layer 3 function, so I dont think your 3560 would be interfering with it if its just doing layer 2 between the routers.

The first thing to check would be the routing back to the source.   After that, verify that you have an RP for the group, and that the 1811 knows how to reach it.  It sounds to me like the 1811 doesnt know where to send the join for the group because it doesnt have an RP defined, or it doesnt know how to reach it.

Hope that helps,


New Member

PIM Joins not switching through catalyst 3560G

Thanks for the reply.

I have the same static RP configured on both routers   (neither is the RP) and I've checked that both routers can ping the RP.    The 1811 must know where the RP is or it wouldn't send the Join,  right?

Are the debug statements a reliable indicator that the Join packets really are being sent?

It  doesn't make sense to me either that the switch would  be droping just  the PIM Joins, but I can't see anything wrong with the  IP routing.

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