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Community Member

Multicasting on the same segment


I am trying to get some clarification on how Multicasting works on the same segment. We have a 3620 router with IGMP Version 1, CGMP, and PIM enabled. The switches are 3548 and 3524's with CGMP enabled. The servers and hosts are all on the same segment.

When we run an Multicast application 'ImageCast'disk cloning software, the traffic is going to the switched ports that have joined the Multicast group as well as the router ethernet port. Which is in turn saturating the router.

My question would be, is this normal behavior for Multicasting or do we have a configuration issue.

Thanks for your help

Community Member

Re: Multicasting on the same segment

First of all, in LAN enviroment you dont need use PIM. PIM is a protocol nessesary when you are distribuing Multicast traffic across many subnet. Second, the problem with router that is receiving multicast traffic, you can avoid enabling "IGMP snooping" in your switches, in this way the switch "snoop" who is requesting the stream and save this information in its CAM table, and then send it, to the only the port that make the request(not all ports, including the router port), in this case will be very weird that the router request the stream, unless you have a link in the router that have conected other clients or subnets on the other side of the link.

Re: Multicasting on the same segment

IGMP snooping doesn't work on 3500. You need PIM sparse mode on the router and CGMP on the switches.




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