Hypothetical configuration question...
Let's say I have 3 WAN connections - 2 of them (WAN1 and WAN2) are good to use, so I want to load balance between them. The 3rd (WAN3) is very expensive to run and should be used only if both WAN1 and WAN2 are down.
What would be the best way to go about setting that up on a Fortigate (101)?
I believe I could use SD-WAN with WAN1 and WAN2 as members to set up the load balancing between those. Would WAN3 also be part of SD-WAN (in a separate zone?) Or would WAN3 just be a normal interface with a default route metric that's higher than the SD-WAN metric? (if both WAN1 and WAN2 are down, will it remove the SD-WAN zone from the routing table?)
Am I going down the right path at least, or is there a better way?