MultiWAN - over LAN - is this possible?

[ant_thomas]

Currently running OPNsense on an old Celeron based HP Chromebox - runs well.

Setup
Onboard Ethernet - LAN
USB Ethernet - WAN - connected to a 4G/5G router. This router is providing an IP via DHCP

Recently moved house and finally got my FTTC connection installed after a number of delays.
I've moved the OPNsense system physically to the location of the FTTC router and have the same setup as above - but using the FTTC router. This also works well.

What I want is to have both the FTTC and 5G routers accessible by OPNsense - but they are at opposite sides of the building. I don't currently have any VLAN capable equipment. Just a simple LAN.


What I have tried is to add another USB Ethernet adapter to the OPNsense system.
Turn off DHCP on the 5G Router
Connect both to the simple LAN
Assign the USB Ethernet adapter a static IP in the 5G router subnet with a gateway of the 5G router
The 5G router and USB Ethernet adapter are on a different subnet to the general LAN (/24 vs /21 for general LAN) and different IP range - no conflicts.
I could see the gateway active and added ping monitoring - I could see it fail when turned off. But couldn't get OPNsense to failover between connections.

Am I attempting to do this the right way?
Is it even possible? (I feel it is as I've been able to see both Gateways at the same time and check their online status)
Should I be using a Virtual IP address and not bother with the 2nd USB Ethernet Adapter?

I won't have a direct physical way to connect both routers to the OPNsense system at the same time.

[Maurice]

VLANs would indeed be better, but your workaround should work, too.
So it's only the failover that doesn't work? Did you enable gateway switching (System: Settings: General)?

Cheers
Maurice