Replacement of existing FortiGate 1200D firewall

Hi mvrcancercentre,

Your current FortiGate 1200D will be End-Of-Support in April 16th, 2026

See the following link for Product Life Cycles for all Fortinet products: https://support.fortinet.com/welcome/#/lifecycle

Based on the current performance-based context, the FortiGate 900G is recommended as the most suitable replacement, offering optimal performance with sufficient headroom for future growth. For higher scalability and long-term data center needs, the FortiGate 1800F can also be considered. The proposed solution will support high availability (HA) deployment and align with current and future network demands.

Additionally, you may review the datasheets of the proposed models for detailed technical specifications

https://www.fortinet.com/content/dam/fortinet/assets/data-sheets/fortigate-1800f-series.pdf
https://www.fortinet.com/content/dam/fortinet/assets/data-sheets/pdf/fortigate-900g-series.pdf

For further clarification and solution alignment, you can also reach out to your local Fortinet partner or the SE Team for expert guidance and support.

If you have found a solution, please like and accept it to make it easily accessible to others.

Regards,
Aman

My personal comment is the 1800F would be probably overkill if you want to go to F-series. Look at the lifecycle document. It's showing even FG-1101E for replacement. Then if you compare it with F-series, likely 1000F would be equivalent or better for performance.
We just finished migrating multiple 1500D HA pairs with 20-30 VDOMs each to 1000Fs. So far, CPU/memory usages are much better than 1500D. Except some NP7 related bugs we encounter time to time, we're happy with the outcome. But those bugs are relatively quickly fixed with newer software maintenance releases.
Based on the numbering vs. performance progression from D->E->F->G-series, I would guess the new 900G (released mid-2023) would be probably about the same with 1000F for performance.  The 900G has the same NP7 as well.

Toshi