I was always under the impression that within a simple L2 network, an IGMP querier was there only to send periodic membership queries so switches can build tables of which port needs to send what and to who. That the querier is just an arbitrary node in the network which someone has decided will send querier messages.
But....
I've just taken some training which very clearly says that the physical network link to a querier needs to have sufficient bandwidth such for all multicast data traffic on the network, because all multicast data traffic will be sent to the querier, regardless of whether it has been requested by a listener or not. That's just not how I thought it worked and seems to go against the whole principle of intelligent multicast data routing / the reason for IGMP in the first place.
Note that my L2 network is not connected by a router to another at L3. In that case, I can see why someone might say 'dimension the link to the router such that it can handle all potential multicast streams' just in case a remote network asked for them. This is strictly a single L2 network using IGMP snooping - no PIM etc.
Who's correct? Me or the training?
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