I'm looking for guidance on implementing WAN failover to the internal 4G modem of my TP-Link MR6400. The closest documentation I could find for my concern uses a second 3G router but what I am aiming for is to use the wired connection as primary and use the router's internal 4G modem as secondary. I have also seen some documentation about mwan3 but I'm not sure how to implement that for the setup I have in mind.
Can anyone help me with this? Any input would be greatly appreciated. Thank you.