Set internet failover on Fortigate 40C on firmware 5.2.3

On the Fortigate 40C, setting the dead gateway detection (aka WAN failover, aka link failover) can only be done by command line interface on firmware 5.2.3.

Why?  I have no idea.  But per support, here are the steps to create failover if WAN1 is your primary circuit:

config system link-monitor
edit 0
set srcintf "WAN1"
set server "8.8.8.8"
set protocol ping
set gateway-ip 0.0.0.0
set source-ip 0.0.0.0
set interval 5
set timeout 1
set failtime 5
set recoverytime 5
set ha-priority 1
set status enable
next
end



If you want to check status of the failover, here is the command:

diag sys link-monitor status

Enabling advanced features in Fortigate firmware 5.0

You can enable some hidden/advanced features in Fortigate OS 5.0 via System -> Config -> Features and turn on Advanced Routing,

In my case, I was looking for "dead gateway detection" so I could switch to my secondary ISP when my primary ISP failed, but the option wasn't there in Router -> Static -> Settings.  Once Advanced Routing was turned on, I had the option for dead gateway detection.