Route traffic to your preferred link when available.
Priority rules specify the connection priority order of the available WAN links (or VPN connections) in which traffic is to be routed. A priority value is configured for each WAN link; the highest-priority available WAN link will be utilized; lower-priority WAN links will be utilized in the priority sequence in the event of WAN link unavailability.
Common use case
For scenarios that you have a main WAN connection to use and leave secondary (more expensive) WAN connections as a backup.