Downgrading often resets SSL VPN ports, HA settings, and VDOM links. Test thoroughly.
Since the 600D is end-of-sale and soon end-of-support, treat firmware upgrades as a stopgap, not a long-term strategy. Plan migration when: fortigate 600d firmware
Ensure you have at least 15% free flash storage and 20% free RAM. Low resources cause upgrade failures. Downgrading often resets SSL VPN ports, HA settings,
