Cast to devices on segregated VLANs

[OpenSourceGuy]

Hello!

I currently have three primary VLANs and interfaces, Lan, IOT, Guest:

• LAN- Common standard LAN; mostly unrestricted WAN access; for trusted home users and devices.
• IOT- Devices that I don't have complete control over; things like smart outlets, google home, smart TV, PS4, etc. Has restricted HTTP access to only WAN.
• Guest- For guests, restricted direct WAN access, no access to anything internal including smart devices

I would like devices on the LAN VLAN to be able to use Airplay and Google's Cast to devices on the IOT VLAN. I have a smart TV which uses Airplay and a Google home on IOT.
I've (unsuccessfully) attempted to use avahi and umdns for reflection across the networks as I am under the understanding that broadcasts will not forward across VLANs.

I was wondering if anyone else has successfully overcome this usability issue and could point me in the right direction! Thanks in advanced for your help!

Configs:
/etc/config/network

config interface 'lan'
	option type 'bridge'
	option ifname 'eth0.1'
	option proto 'static'
	option ipaddr '192.168.1.1'
	option netmask '255.255.255.0'
	option ip6assign '60'

config interface 'IOT_Seg'
	option proto 'static'
	list ipaddr '192.168.5.1/24'
	list dns '192.168.1.1'
	option ip6assign '64'
	option type 'bridge'
	option ifname 'eth0.3'

/etc/config/firewall:

config zone
	option name 'lan'
	option input 'ACCEPT'
	option output 'ACCEPT'
	option forward 'ACCEPT'
	option network 'lan'

config zone
	option name 'wan'
	option output 'ACCEPT'
	option masq '1'
	option mtu_fix '1'
	option network 'wan wan6'
	option input 'DROP'
	option forward 'DROP'

config zone
	option network 'IOT_Seg'
	option input 'DROP'
	option forward 'DROP'
	option name 'IOT_Seg'
	option output 'ACCEPT'

config rule
	option dest_port '67-68'
	option src 'IOT_Seg'
	option name 'IOT Allow DHCP'
	option target 'ACCEPT'
	list proto 'udp'

config rule
	option dest_port '53'
	option src 'IOT_Seg'
	option target 'ACCEPT'
	list proto 'tcp'
	list proto 'udp'
	option name 'IOT allow DNS'

config forwarding
	option dest 'wan'
	option src 'IOT_Seg'

[dlakelan]

Most of these things use multicast I believe. You need to look into multicast routing. It's definitely nontrivial.

[vgaetera]

• Chromecast across two subnets
• Multicast across subnets - smcroute

[OpenSourceGuy]

Most of these things use multicast I believe. You need to look into multicast routing. It's definitely nontrivial.

Thanks! I completely missed multicast! I added and configured smcroute and permitted IOT traffic to multicast off my router.

Thank you as well @vgaetera, That second article helped lead me in the right direction, once I figured out debugging with smcroute and the specific multicast address for my google home (239.255.255.251) things started to work.

If anyone comes across this in the future, don't forget to increase the TTL for multicast using firewall rules, doing so greatly increased stability of the data.
Now to figure out why my sound bar isn't available to cast..