In an SD-WAN rule, you can steer application traffic by using Internet Service Database (ISDB) entries. Facebook and LinkedIn are predefined ISDB objects in FortiGate, so the correct way is to select them in the Internet service field under Destination. This ensures that all traffic to these applications is matched and routed through the chosen (less costly) link. 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.