Fortinet SD-WAN integrates advanced security with dynamic WAN management to optimize network performance. However, issues such as poor connectivity, application slowdowns, or misrouting can arise. Here are key troubleshooting techniques to resolve common SD-WAN issues in Fortinet environments:

Verify WAN Link Health and SLA Performance

SD-WAN decisions are driven by link performance metrics such as latency, jitter, and packet loss. Start by checking the health of each WAN link using FortiGate’s monitoring tools, like FortiView. Ensure links meet the Service Level Agreement (SLA) thresholds you’ve configured. If a link’s performance drops below SLA standards, it could lead to degraded application performance or improper traffic routing.

Review SD-WAN Rules and Traffic Steering Policies

SD-WAN routing relies on user-defined traffic steering policies to determine which paths traffic should take based on application requirements and link conditions. If traffic isn’t being routed optimally, examine these policies for accuracy. Misconfigured rules can cause critical applications to be routed over suboptimal links, resulting in slow performance. Ensure that priority applications (like VoIP or SaaS) are routed based on current link performance.

Monitor Application Performance

FortiGate provides real-time visibility into how applications are performing across WAN links. If an application is performing poorly, it may be routed over a congested or failing link. Use the SD-WAN monitor to assess application traffic and adjust SD-WAN policies as needed to ensure important applications are prioritized and routed over the best-performing links.

Inspect VPN Tunnel Stability

In Fortinet SD-WAN setups, VPN tunnels connect remote sites securely. If there are communication problems between locations, verify the status of these VPN tunnels. Any misconfigurations or failed tunnels can disrupt traffic flow and lead to network outages across remote offices or data centers.

Test Failover Mechanisms and Routing

Fortinet SD-WAN should automatically reroute traffic when a WAN link fails. Test failover by simulating link failures and confirming that traffic is properly rerouted to a healthy link. Additionally, verify routing configurations to ensure that traffic is taking the most efficient paths across the network.

By focusing on these areas—link health, traffic steering, application performance, VPN stability, and failover—you can troubleshoot and resolve most Fortinet SD-WAN issues effectively.