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Occasional Contributor


I’m working to configure our network to handle multicasting.  We’ve been a flat single router network until just recently.  We now have a central core switch (S7910E) and then a layer 3 switch (either 4800G or 5500G depending on campus) doing routing at the edge of each campus subnet and connecting back to the core via ospf.  All end-point switches are 4500Gs and have IGMP-Snooping enabled by default. 

 I’m confused as to whether setting the network core as an IGMP-querier is enough or if I need to declare the router’s on each campus as queriers as well?  I’ve read that if I set multiple layer 3 devices as queriers, they do an election and the lowest numerical IPed device wins.  I’ve also read that election fails sometimes and causes havoc with multicast streaming so I’d like to declare only the one querier if I can get away with it.  If that core switch goes down, clients won’t be able to reach the multicast source anyways so the redundancy afforded by multiple queriers is moot.  Thoughts?

The goal here is fast Ghost sessions and some multicast video distribution.

This message was edited by kevinadams on 6-4-10 @ 4:22 PM
Trusted Contributor

Re: IGMP-queriers

Hi Kevin

It's more complex then you think. The Short answer is: You have to active PIM-DM on all Layer3-Interface to enable Multicast-Route-Exchange.

More infos you will find in the Manual, here is a config example:


Kind regards





H3CSE, MASE Network Infrastructure [2011], Switzerland