Campus Multicasting

Unanswered Question


I have a basic multicast scenario that I am deploying with a VSS 6500 in the core with 4948 connecting to the VSS 6500 hosting the multicast server. I then have the multicast clients connecting via 3750E's that also connect to the VSS 6500.

On the VSS core I have enabled multicast routing and pim dense mode on the SVI Layer 3 interfaces connecting to the multicast server segment aswell as to the access device segment.

On the 4948 and the 3750E, I have enabled "ip igmp snooping" globally.

I am not receiving any multicast traffic on my client device.

Am i missing something ?


I have this problem too.
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JamesLuther Mon, 04/06/2009 - 07:52


To me this setup sounds like it should work. Please post the output of "sh ip mroute" from the core router, are you seeing the multicast group being forwarded out of the access layer Vlan?

Also look at "sh mac-address-table multicast igmp-snooping" on the access layer switches to see if the client ports are registered against the multicast group.

igmp snooping is not required to get this working, it is just a feature to limit the ports the multicast stream are sent to in a layer 2 network. In fact I've seen it cause problems in some multicast implementations.


Jon Marshall Mon, 04/06/2009 - 08:53

I agree with James, it does sound like you have configured the basics to get it going.

One thing worth checking is the TTL the server sets in the multicast app. If TTL is set to 1 then it will only stay local to the server subnet. Basically you need to factor in the maximum number of L3 hops from server to client and set the TTL to be greater than that.

The TTL is set by the server application.



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