Before you can configure FortiGate interfaces as SD-WAN members, you must remove or redirect existing configuration references to those interfaces in routes and security policies. This includes the default Internet access policy that's included with many FortiGate models. Note that after you remove the routes and security policies, traffic can't reach the WAN ports through the FortiGate.
Redirecting the routes and policies to reference other interfaces avoids your having to create them again later. After you configure SD-WAN, you can reconfigure the routes and policies to reference the SD-WAN interface.
- Go to Network > Static Routes and delete any routes that use WAN1 or WAN2.
- Go to Policy & Objects >IPv4 Policy and delete any policies that use WAN1 or WAN2.