When asymmetric routing is observed (such as reply traffic not following the optimal path), the solution is: " The auxiliary-session feature, enabled under config system settings, allows FortiGate to consider multiple egress interfaces for reply traffic, not just the original ingress interface. This is crucial for SD-WAN environments where the best path may differ between forward and return directions, especially when performance or policy rules are dynamically evaluated. " Activating this ensures reply traffic is always sent on the member with the best real-time metrics.References: 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.