In which order does FortiGate consider the following elements during the route lookup process?

In FortiOS (including FortiOS 7.6), FortiGate follows a strict and well-defined route lookup order when determining how to forward traffic. This order is critical for understanding SD-WAN behavior and is explicitly referenced in the FCSS SD-WAN curriculum. The correct lookup sequence is: Among the options provided, only Option D correctly reflects the beginning of this sequence by placing policy routes first, followed by ISDB routes, then SD-WAN rules, and finally static routes (representing the routing table). Therefore, the correct answer is D. An operational review should distinguish the rule that matches the traffic from the interface that is ultimately selected. Valid forwarding also depends on destination route eligibility, current member state and the applicable SLA or quality-selection algorithm. A diagnostic showing configured members alone is not conclusive evidence that all those members will carry a particular flow. When troubleshooting, correlate the configured SD-WAN service with diagnose sys sdwan service4, the live session entry and the routing table. An application signature, an IP route and a health-check result describe different decision stages; treating them as interchangeable can produce incorrect conclusions about the egress interface.