I have a pfsense configured with dual wan set up as failover. The primary would be my ISP (xfinity) and the backup is a slower 4G connection. I've tested the setup and can see that when the primary WAN (xfinity) goes down, traffic fails over to the slower 4G backupcinema hd.
However, I have noticed that when the primary recovers, pfsense does not switch traffic back and leaves traffic running off the slower 4G backup.
I have to manually down the backup interface for pfsense to redirect traffic back to the primary WAN. Is there a way to have failover to the backup 4G WAN but restore back to the primary xfinity WAN when it recovers automatically?
Based on information you provided, my best guess is that the traffic is SNATed. So when primary link fails, session is forced to go via another ISP, because route stops to exist. But when primary link recovers, if session is SNATted, it is not forced (route still exist). This setting should help to resolve this: