Hardware Requirements for Failover

[SomebodySysop]

Running OPNSense 22.1 router software on an amd64 system with only 2 ethernet ports (WAN/LAN).  Connected to internet using ATT BGW210-700 router in passthrough mode.  Image of my current setup is attached.

Current WAN1 is wired ATT broadband.  I just purchased an LTE cellular modem which I would like to add as WAN2 in an OPNSense failover setup. 

1. Do I need to upgrade my router hardware to a system with at least 3 ethernet ports?
or
2. Is there some other way to achieve WAN1 to WAN2 failover to LAN with existing 2 port router?

[SomebodySysop]

Looks like I solved this one.  Did not need to upgrade my existing hardware config.  I can plug the LTE modem into my current hub.  See the attached diagram.

1. I set my LTE cellular modem to bridge mode and assigned it a static IP on my LAN.
2. I plugged the LTE modem into my network hub.
3. In OPNSense, went to: System: Gateways: Single and added the LTE modem as a gateway (IPV4, LAN interface).  https://docs.opnsense.org/manual/gateways.html#
I entered a monitor IP and did NOT disable gateway monitoring.
4. Went to: System: Diagnostics: Services and turned dpinger ON for the new gateway.

Verified that LTE gateway is "online" and dpinger is returning RTT results on System: Gateways: Single page.

My next step will be to configure failover, but for now I at least know that I can add a gateway to my existing configuration.

[SomebodySysop]

Update.

Configured failover following this guideline: https://docs.opnsense.org/manual/how-tos/multiwan.html

BGW210-700 router --> OPNSense router --> Network Switch <--- Netgear LTE LM1200 Modem Router

It works.  When BGW210 is unplugged, WAN gateway switches to LTE LM1200 modem.

Update 08/30/2022.

Documented the process here: https://youtu.be/WG0Mh4Ts9GQ

[nVIceman]

Thanks for documenting this, but after trying it, the LTE gateway shows offline the whole time when dpinger keeps checking it. I had to temporarily put it in router mode just to change IP to one that is my in LAN, but I cannot access or ping that IP I gave it after setting it up as gateway or even before. As soon as I unplug from my computer and attach to network switch, it never seems to get online to the IP that is available for it to go to.

Any suggestions of what to try, why it would not get on the network?