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Layer 3 Multicast - IGMP / RGMP


I am configuring multicast in a environment where I have a 4506 at each site (4 total) and a 6506 as the core. 

Each 4506 is connected via layer 3 to the 6506.

I have a mix of 3560s, 3548s, and 2960s connected to the 4506s and the 6506 via layer 2 trunk

I have multiple multicast sources and hosts communicating at a time (multiple cameras sending video / multiple computers receiving video)

Sample Diagram:



6506 --> 4506 --> 3548

   |            |

   |            --> 2960


4506 --> 2960




I configured ip multicast-routing on each of the 4506s and on the 6506. 

IGMP snooping is on by default on the 3560 and 2960 switches.

CGMP is on by default on the 3548 switches.

PIM sparse-dense mode and IGMP version 3 is on each of the layer 3 interfaces for the 4506s and 6506 where they connect and on each VLAN that is sending or receiving multicast

Multicast is working throughout the network, however at times I am getting large packet loss and I suspect possible a configuration issue...

Some questions I hope someone can answer:

#1 - Since the 3548s do not support IGMP, do I need to enable CGMP on the 4506 and 6506 layer 3 interfaces?  Will this work with having IGMPv3 also on the interface?  Or does it automatically handle the CGMP?

#2 - Since each 4506 and 6506 has multicast routing enabled, therefore each is a multicast router, do I NEED to impliment RGMP?  Will this conflict with the CGMP switches (3548s)?

#3 - Is there any other configuration I should be considering?

Thanks in advance


Layer 3 Multicast - IGMP / RGMP


In response to your Question #3, I would suggest you try the suggestion by Peter Paluch in:



New Member

Layer 3 Multicast - IGMP / RGMP

I have layer 3 routing so that would not apply here I believe.

New Member

Layer 3 Multicast - IGMP / RGMP


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