I have 2 home networks, the family network (call it “Fam”) and an IoT network (call it “Dev”). The Sonos devices are on the IoT, as are my Apple HomePods (which I use for voice control). The family’s iPhones are on the family network. The two networks can see and address one another, although they are on different netblocks. At the moment there is no firewall between the two networks.

Devices on Fam can see the Sonos speakers. For instance, I can ping them from my computer. But I cannot AirPlay to them, and they do not show up on in the Sonos app. I cannot control them from Siri on the Fam device. If I switch the device to Dev, it can see the Sonos devices, identify them in AirPlay, and control them.

It used to work across networks until I switched the Fam network to a new device. The biggest relevant difference I can see is the new Fam network requires a new netblock. So my guess is that AirPlay and other device discovery is just using the broadcast IP on the netblock to find the Sonos speakers. If so, I should be able to fix this just by getting everyone on the same netblock. Can someone confirm that is what is going on?