I am setting up set up several multicast audio streams on my LAN. I am using vlc on a Linux box to transmit the streams using a command line of the form:
/usr/bin/vlc -I dummy --sout '#rtp{dst=224.0.0.0,port=5004,sap,name=test}' --no-sout-all --sout-keep --repeat --quiet test.mp3
This configuration will send out an audio stream on the specified multicast group, as well as SAP announcements on the well-known SAP multicast group. On the receiving side I have a Windows 10 PC on which I plan to run vlc as a client to "tune in" to one of the multicast streams and play it back through the PC speakers. The Linux box and the Windows box are connected to a switch which in turn uplinks to the rest of my network. I would obviously like to avoid hammering the rest of my network with RTP packets from these audio streams; to that end, I connected these two machines to a switch which supports IGMP Snooping. The expected behavior is that the multicast traffic will not be forwarded to a port on the switch unless a machine connected to that port has issued an IGMP Join request (which the switch sniffs out from the traffic). However, that's not the behavior I see - instead, using Wireshark I see ALL multicast traffic forwarded to ALL ports on the switch, even if the machine on that port has not issued any IGMP Join packets (i.e. I have NOT yet launched the vlc client on the Windows machine). My understanding is that flooding all ports with copies of all multicast packets is the default behavior for a switch.
I have tried several switches which claim to support IGMP Snooping, including a TP-Link TL-SG108, a TP-Link TL-SG116, a Cisco SF200-24P, and a Trendnet TPE-80WS. ALL of these switches exhibit the same "flooding" behavior, copying all multicast packets to all ports on the switch. In the case of the Cisco, I followed the instructions here (https://www.cisco.com/c/en/us/support/docs/smb/switches/cisco-small-business-200-series-smart-switches/smb94-configure-internet-group-management-protocol-igmp-snooping-o.html) to configure the switch for IGMP Snooping, but to no avail. The Trendnet switch has similar settings in its management web interface, whereas the TP-Link switches don't appear to have any management web pages at all.
So my questions are these: Can someone confirm that my understanding of how IGMP Snooping is supposed to work is correct? And, if so, any suggestions for getting one of these switches configured correctly? Is there a better/easier to configure model of switch to use for this purpose?
