Load balancing : Load balancing among links : Link load balancing for outbound traffic : Routing outbound traffic through a link
 
Routing outbound traffic through a link
To define each of your load balanced links for this point of presence, enter the IP address of the next-hop router (gateway) for each ISP’s link, as well as a weight that will determine how much of outgoing sessions it should receive. (Outbound sessions will be distributed by a weighted round-robin method. Links whose Weight setting is greater will receive a greater proportion of traffic.)
If you want FortiADC to avoid the link if a crucial IP address is not accessible through it, also select a link health check (“Monitoring link health or availability”).
To define your ISP links, go to Link Load Balance > Outbound > Gateway.