i bought a 4G MODEM that was listed on the known working modem list for pfsense.
My question is the following:
Is it possible to configure a fail over WAN with 1 USB 4G MODEM and 1 ethernet cable to the NIC.
i know its possible with 2 ethernet lines but i really want to make it work with 1 dedicated line and a failover 4G modem in case the land line fails.
As long as pfSense sees the modem and can use it like a WAN, it should work fine. Same as any other Multi-WAN setup. You will probably want to disable gateway monitoring on the 4G modem so it doesn't consume bandwidth for the monitoring traffic.