“This slide shows the SD-WAN rule lookup process. SD-WAN rules are essentially policy routes.”
“FortiGate performs a forwarding information base (FIB) lookup for the packet destination IP (dstip). If the resolved interface for the fib-best-match isn’t an SD-WAN member, then FortiGate moves on to the next rule. This behavior follows the key routing principle: SD-WAN rules are skipped if the best route to the destination isn’t an SD-WAN member .”
“If the resolved interface is an SD-WAN member, then FortiGate looks for one or more acceptable members in the oif list... An acceptable member is an alive member that has a route to the destination. This behavior follows the key routing principle: SD-WAN rules are skipped if none of the configured members in the rule have a valid route to the destination .”
“Because regular policy routes have precedence over any other routes...”
“Also note that policy routes have precedence over SD-WAN rules, and over any routes in the FIB.”
Technical Deep Dive:
The correct answers are A, C, and E .
A is correct because an SD-WAN rule is not enough by itself. A selected member must also be alive and have a valid route to the destination. If none of the members referenced by the rule can actually reach the destination, the rule is skipped.
C is correct because a regular policy route is evaluated before SD-WAN rules. This is a classic exam trap. FortiGate treats SD-WAN steering like policy-route logic, but standard policy routes still win if they match and are valid.
E is correct because FortiGate first checks the FIB best match . If that best route resolves to an interface that is not an SD-WAN member, FortiGate skips the SD-WAN rule and continues.
Why the others are wrong:
B is false because SD-WAN rules do not have precedence over everything; regular policy routes do.
D is false because the number of available routes is not the deciding rule. Even with only one route, SD-WAN can still steer traffic if the routing and member conditions are met.
Operationally, think of SD-WAN routing in this order: policy route check → SD-WAN rule lookup → standard FIB fallback . On FortiGate, the practical validation commands are:
get router info routing-table all
diagnose sys sdwan service
diagnose firewall proute list
That combination lets you confirm whether a packet is being captured by a policy route, whether an SD-WAN rule has acceptable members, and what the FIB currently resolves for the destination.
