6.0.5 → 6.0.10 → 6.0.15 → 6.0.18
You cannot simply jump from an old version (like 5.2 or 5.4) straight to 6.0.17 without risking configuration corruption. For a high-quality installation, you must follow the supported migration path: Fortinet FortiGate 200D - AVFirewalls.com fortigate 200d latest firmware extra quality