I have a network consisting of two HP 2810 switched. Attached to each switch is, on one port, a multicast video coder, and on a different port, a decoder.
There are two VLANs – a control VLAN (running on the default VLAN) and a video VLAN. Ideally, I would like to use IGMP snooping on the video VLAN.
If I turn off IGMP snooping on the switches, the decoders can decode the stream from either the local coder or the remote coder. However, if I turn on IGMP snooping, the decoder can only join the multicast group on the local switch. It would appear the the IGMP requests do not get passed on to the other switch when a decoder requests to listen to the stream from the remote coder.
I want the system to work bi-directionally – e.g., a decoder on either switch can listen to the stream from the local coder or remote coder.
What do I need to configure on the switches, and how?
Best Answer
This is an all too common problem. Snooping requires either a full multicast router, or an igmp querier in the network (one per broadcast domain.) Both periodically send out multicast group requests to learn who's interested in what. That information has a lifetime (usually a multiple of the query interval, which is 125s by default), so after a few minutes without a querier, your multicast streams simply stop. (or the switch begins flooding to all ports, which is the opposite of the intent of enabling snooping)
The command is:
vlan ## ip igmp querier