Fortinet SD-WAN is a powerful solution that helps businesses manage and secure their wide area networks. It improves application performance, saves costs, and provides better visibility across the network. Whether you're a network engineer or preparing for Fortinet NSE 8 training, understanding how to troubleshoot SD-WAN issues is a valuable skill.

In this blog, we’ll go through some common Fortinet SD-WAN issues and how to fix them in a simple, easy-to-understand way.

1. Issue: SD-WAN Not Selecting the Best Link

What’s happening?
Sometimes, SD-WAN doesn’t choose the most reliable or fastest link, even when it’s available.

Possible Fixes:

        • Check your SLA (Service Level Agreement) settings. Make sure you’ve defined the correct thresholds for latency, jitter, and packet loss.
        • Ensure link monitoring is turned on and working correctly.
        • Review SD-WAN rules to confirm they’re set up based on application type or performance.

        2. Issue: Applications Not Following SD-WAN Policies

        What’s happening?
        Some applications might not be routed through the expected path.

        Possible Fixes:

          • Double-check your SD-WAN rules to make sure they are matching the correct traffic.
          • Use application control features to identify apps accurately.
          • Ensure DNS settings are correct, as misconfigured domains can cause apps to be misclassified.


          3. Issue: High Latency or Packet Loss

          What’s happening?
          Users may experience slow applications or voice call drops.

          Possible Fixes:

            • Use real-time monitoring tools to find out which link is performing poorly.
            • Try switching traffic manually to another link and test again.
            • Check with your ISP for any known outages or congestion.


            If you're working towards your Fortinet NSE 8 certification, this kind of hands-on troubleshooting experience can help reinforce your understanding of SD-WAN behavior in real networks.

            4. Issue: VPN Tunnels Going Down

            What’s happening?
            Your SD-WAN VPN tunnels are disconnecting or unstable.

            Possible Fixes:


              • Recheck the IPsec tunnel configurations on both ends.
              • Confirm that routing settings are correct and consistent.
              • Make sure you're using the latest firmware version to avoid known bugs.

              5. Issue: Configuration Sync Issues Between Branch Devices

              What’s happening?
              Branch devices aren't syncing configuration properly.

              Possible Fixes:


                • Use FortiManager to manage configuration templates across devices.
                • Check if administrative domains (ADOMs) are correctly set up.
                • Ensure the central management system is properly linked with all devices.

                Final Thoughts

                Fortinet SD-WAN is a robust and smart technology, but like any system, it needs proper configuration and regular health checks. By understanding these common issues and how to fix them, you’ll be better prepared to handle real-world network challenges.

                If you're planning to take the fcx certification or already on your journey with Fortinet NSE 8, troubleshooting practice like this gives you the edge. Whether it’s preparing for an exam or managing a live network, knowing how to solve these problems is key to success.