@Duckmuck hey, I'm also trying to get my Sonos Setup working in different VLANs.
My Speakers are in VLAN IOT, subnet 10.0.2.0/24 (not really, but let's assume)
My phone which is supposed to be the controller is in LAN, subnet 10.0.1.0/24.
Which one do I have to setup as upstream and which one as downstream and which subnet has to be entered in which Interface. I see IGMP traffic in the general system logs, like group membership requests, but at the same time I see "IGMP came from myself, ignoring".
Would be appreciated if you could help out