You configured an SD-WAN rule with the best quality strategy and selected the predefined health check, Default_FortiGuard, to check the link…

The "Best Quality" SD-WAN rule strategy operates in a specific sequence. First, FortiGate evaluates all available member links against the SLA targets defined in the specified profile (Custom-profile-1). Only the links that meet these thresholds for latency, jitter, and packet loss are considered eligible. From this subset of compliant links, FortiGate then selects the single best link based on a calculated quality score. If multiple links share the same best quality score, the member's position in the configuration list (interface preference) is used as a tie-breaker. Option C is the only choice that correctly identifies the initial, mandatory filtering step of meeting SLA targets.

A. Latency – Member configuration order – Link cost threshold

This is incorrect because it omits the initial SLA compliance check and incorrectly singles out latency, whereas jitter and packet loss are also evaluated.

B. Link quality index – Member configuration order – Link cost threshold

This is incorrect because it fails to mention the crucial first step of filtering links based on whether they meet the SLA targets.

D. Latency – Jitter - Packet loss – Bibandwidth – Member configuration order

This option lists the metrics used to calculate link quality but does not accurately represent the sequential decision-making process of the SD-WAN rule.

1. Fortinet FortiOS 7.6.0 SD-WAN Administration Guide, Page 51, "Best Quality" section.

The document states: "FortiGate first determines which SD-WAN members meet the SLA. From this subset of members, FortiGate chooses the one with the best link quality." This directly supports that the first step is identifying "Links that meet the SLA targets".

It further clarifies the tie-breaking mechanism: "If multiple members have the same best link quality, FortiGate uses the interface preference to break the tie. The interface preference is determined by the order that the interfaces are added to the SD-WAN." This supports the "Member configuration order" component, although it is a tie-breaker.