I've been working with this on and off for a few months trying to move my Chromecasts into my IoT VLAN. But try as I might I simply cannot get them working. Does anyone know of a comprehensive guide to get these up and going? I've setup MDNS Repeater, UPD Broadcast Relay, etc. not 100% sure they are even properly configured. But I just can't make this work. So I'm missing some key step I would guess. Doesn't help that I don't fully understand the communication with the Chromecast.
First of all i don't have a direct answer to your question.
But i do have a Chromecast in a separate VLAN network. I don't send the Chromecast traffic into the regular LAN. Instead i just use the IOT WLAN on the Chromecast control devices (mobile, tablet).
The downside is that i sometimes have to switch the network on my mobile.