Help with AirPlay/Chromecast Across Subnets (mDNS Not Working)

[Middiu]

Hi there,

Let me start by saying that I'm not a network engineer, and this isn't my field of expertise, so I might get a few things wrong — apologies in advance!

I recently rebuilt my home network and installed OPNsense on a mini PC (n150).

Here's a summary of my setup:
   •   OPNsense Firewall
   •   igc0 → WAN
   •   igc1 → LAN (192.168.1.1/24) → connected to an Amazon Eero 7 (router mode), which creates a subnet: 192.168.4.0/24 (for all my WiFi devices: phones, iPads, laptops)
   •   igc2 → LAN2 (192.168.2.1/24) → connected to a TP-Link switch, which connects wired devices like my TV, Xbox, and Soundbar

⸻

🛠 Problem

Everything works fine except AirPlay and Chromecast:
Devices on WiFi (192.168.4.x, via Eero) cannot see or cast to devices on 192.168.2.x (TV, etc.).

⸻

🔍 What I Tried
   •   Installed the mDNS Repeater plugin
   •   Enabled it on both LAN (igc1) and LAN2 (igc2)
   •   Temporarily set up "allow all" firewall rules on both LAN and LAN2 for testing

Despite this, devices on WiFi still cannot discover the TV or other devices on the .2.x network when trying to cast or AirPlay.

⸻

❓ Questions
   •   Is this setup technically achievable given the current network layout?
   •   Is mDNS Reflection the correct approach across these 3 different subnets?
   •   What else can I check or try to debug this issue?
   •   Would putting the Eero into bridge mode help here?

Any advice or troubleshooting tips would be really appreciated!

Thanks,
Emilio

[meyergru]

The problem is that your Eero does not create a subnet, but rather creates a whole separate network.

Up to this point, we cannot even tell if it does NAT on its "WAN" interface (in the LAN). It sure does not know anything about a separate 192.168.2.0/24 subnet. Also, your OpnSense does not know anything about the 192.168.4.0/24 network, so all the routes are missing.

It would be a whole of a lot easier if the Eero 7 would be restricted to being a purge AP in bridge mode, so alle of its devices appear to be in the LAN subnet.

[Middiu]

The problem is that your Eero does not create a subnet, but rather creates a whole separate network.

Up to this point, we cannot even tell if it does NAT on its "WAN" interface (in the LAN). It sure does not know anything about a separate 192.168.2.0/24 subnet. Also, your OpnSense does not know anything about the 192.168.4.0/24 network, so all the routes are missing.

It would be a whole of a lot easier if the Eero 7 would be restricted to being a purge AP in bridge mode, so alle of its devices appear to be in the LAN subnet.

thanks for the reply.

Unfortunatelly Eero stops working as soon as I switch to "bridge" mode, and I don't believe it's an OPNSense issue, or at least I don't know how to confirm it.

I regret buying an Eero device, it doesn't allow any advanced configuration, it doesn't even have a local web interface to configure it, you have to go through your Amazon account.

[cookiemonster]

Maybe you don't have to go via your amazon account. I use an eero mesh with OPN and do it via the app. But then my eeros were ISP branded, so there are likely to be differences.
What is the same and of this I'm sure from the documentation, is that when you put it on bridge mode, as expected most functionality is disabled. Not a loss, as that'w what you want OPN to take those over i.e. dhcp reservations, dns servers, etc.
You need to find which one is your eero gateway. That is the one to put in bridge mode, not any of the "satellites".
Once you put it in bridge mode, it will get its ip address from OPN, so you need to find it there. But it will simply be a "ip LAN client".