Making changes to the FortiGate management IP address
Occasionally a FortiGate device will need to make a change to its IP address. If the IP address change allows the FortiGate to recreate its path to the FortiManager unit, functionality will remain unchanged. However, if that change breaks connectivity, after 15 minutes the FortiGate unit will revert to its last known good configuration in an attempt to restore connectivity.
The 15 minute timer is hardcoded and cannot be configured or disabled.