Recently, I faced an issue with mwan3, a package on OpenWrt routers that is designed to manage multiple internet connections, either for load balancing or a failover.
At work, we have two fibre connections, where the main one is used primarily and the second is online, but only activated when the first goes down – typical failover approach.
First connection (lets call it fibre) is with metric 10 wheras second connection (fibre2) is with metric 20.
For tech guys, first fibre is uncontended with static IP, whereas our backup fibre is contended over PPPoE.
My main policy in mwan3 is fibre_fibre2.
fibre_fibre2 policy contain fibre_m1_w3 (Metric 1, Weight 3) and fibre2_m2_w2 (Metric 2, Weight 2) member.
When fibre is down, the fibre2 takes over and all traffic flows through nicely, almost.