: Go to System > Firmware and upload the file manually.

Use the Fortinet Upgrade Path Tool to see the mandatory "hops" or intermediate versions you must install first. 3. Installation Steps

Experts and community members typically suggest sticking to "mature" releases that emphasize stability over new features for this older hardware.

Keeping your FortiGate 100D firmware up-to-date is essential for ensuring the security and performance of your network. By following the steps outlined in this piece, you can easily download and install the best firmware for your device. Remember to always check the Fortinet Support website for the latest firmware versions and to follow best practices for updating your device.