FCSS_SDW_AR-7.6 Exam Dumps : FCSS - SD-WAN 7.6 Architect

The use of SLA targets is specific to certain SD-WAN strategies. The "Lowest Cost (SLA)" and "Maximize Bandwidth (SLA)" strategies are explicitly designed to use the configured SLA targets to make routing decisions. The "Best Quality" strategy uses performance metrics but does not necessarily require or reference SLA targets in the same way, while "Manual" does not use metrics at all for path selection.

This is a core function of SD-WAN rules with SLA targets. The purpose of configuring an SLA target with specific thresholds for latency, jitter, and packet loss is to define what is considered "acceptable" performance for an application. SD-WAN rules then use these targets to check if the members (interfaces) meet these requirements before a flow is steered over them, ensuring that a preferred path still offers a good user experience.

FortiGate allows for a single SD-WAN rule to reference multiple, different performance SLAs. This is crucial for complex deployments where a single SD-WAN rule needs to handle traffic for multiple applications that have distinct performance requirements. For example, a single rule might direct VoIP traffic based on one performance SLA with strict latency/jitter targets, while simultaneously handling general web traffic using another performance SLA with more lenient requirements.

The SD-WAN rule (config service edit 1) is configured with set mode priority. This means the rule selects the best interface based on a defined performance metric, as opposed to a simple static priority or SLA. The event log (image_41cfb5.png) shows Metric latency and Message Service prioritized by performance metric will be redirected in sequence order. This indicates that the rule is using latency to determine the preferred member. Given that the log message is about a change, and the most logical reason for a change in a priority mode is that a different member is now the best performer, it implies that the latency on port2 has become lower than that on port1.

The log message Service prioritized by performance metric will be redirected in sequence order confirms that FortiGate is changing the member being used for this service. Because the mode is priority, FortiGate dynamically selects the member that currently meets the best performance criteria, which in this case is latency. The log implies a new member has been selected as the most optimal, and with the default configuration, the members are sorted based on their performance, so the outgoing interface list is effectively updated to prefer the new best-performing member (port2).

This configuration demonstrates a typical IPsec setup for SD-WAN overlays where the hub side requires a manually defined tunnel IP address, and the spoke can be flexibly configured, including interoperability with third-party IPsec devices. As described in the Fortinet SD-WAN Architect Guide: “For some overlays, the tunnel interface IP is configured statically on the hub side, which allows more control over overlay subnetting and facilitates the use of user-defined overlay IP addresses. This approach is also a requirement for compatibility with non-FortiGate endpoints, such as third-party IPsec devices that may not support dynamic address assignment via IKE or proprietary mechanisms.” This enables hybrid SD-WAN environments and advanced designs involving external partners or cloud services. Overlay IP flexibility is critical for route control and segmentation.