A substation has two egress paths to the NOC: a fibre link and a cellular modem, both terminated on the same FortiGate and both currently healthy. The utility wants outbound telemetry traffic automatically split across both links based on real-time latency and jitter measurements, rather than always preferring one link unless it fails outright. Which approach fits this requirement?

SD-WAN in FortiOS groups the fibre and cellular interfaces as members of one virtual interface and continuously measures each member against a performance SLA target, tracking metrics like latency, jitter, and packet loss; an SD-WAN rule using the best-quality (or lowest-cost SLA) algorithm then steers new sessions to whichever member currently meets the criteria, which is exactly the real-time, quality-based split the scenario asks for. Two static routes at equal priority produce ECMP, which spreads sessions across both links by a hashing algorithm, not by measured link quality, so a degraded-but-still-up link keeps receiving its share of traffic. Static route priority is a fixed administrative preference the engineer sets once; it never re-evaluates itself against latency or jitter, and the lower-priority route only activates when the preferred route is withdrawn entirely, not when it merely gets slow. Link health monitoring on a single static route only detects reachability failure of that one route's target; it has no concept of comparing performance across two links and does not produce load-balancing behavior on its own. To confirm SD-WAN is steering correctly, check the SD-WAN performance SLA status and the session's selected interface in the GUI or CLI and verify it changes as one member's measured latency degrades.