Active client-side policy
Add an active policy to the client-side FortiGate unit by turning on WAN Optimization and selecting active. Then select a WAN optimization Profile. From the CLI the policy could look like the following:
config firewall policy
edit 2
set srcintf internal
set dstintf wan1
set srcaddr client-subnet
set dstaddr server-subnet
set action accept
set schedule always
set service ALL
set wanopt enable
set wanopt-detection active
set wanopt-profile default
next
end