Failover ISP

Hi,

I have a task to double check a Fortigate's  configuration, the device is a 60F. This device has 2 WAN/ISP and obviously for failover in case the primary fails.

Recently, the primary did went down and all the users in the office didn't have internet connection, so was told by the onsite folks that the failover didn't kick in.

So I login to their Fortigate and the first thing I've check are the Network interfaces.

these are just sample IP's

WAN1: 76.22.33.44 /30 Static 

WAN2: 192.168.100.x /24 DHCP

Internal: 10.10.1.0 /24

The first thing I noticed is WAN2 which has a class C IP and instead of Static, it's set to DHCP/Dynamic. Not sure if this was set by their previous IT before we took them.

Below the 2 WAN/Outside interfaces is an SD-WAN Zone link which links both WAN1 and WAN2

The next thing I check are the Static Routes both WAN1 and WAN2 have a default routes

WAN1: 0.0.0.0/0   

             76.22.33.43(GW IP)

             Administrative Distance 10

             Priority 1

WAN2: 0.0.0.0/0

              Dynamic Gateway (192.168.100.1)

              Administrative Distance 20

              Priority 1

I don't know if the reason WAN2 is on class C ip is possibly it's connected to like a Cradlepoint/hotpspot from Verizon or AT&T or etc. 

I do see Admin Distance one is lower and one is higher but I might be missing something to check

I also see a policy from internal to SD-WAN link for Outbound

I did ping from source WAN1 and WAN2 and only WAN1 is working so not sure if this is enough to answer my question but kind of paranoid and maybe I still missed something to check

Thanks

Jeff