Maximum number of flow rules limited by hardware
For all FortiGate-6000 and 7000 models, the CLI allows you to add up to 512 flow rules. However, the number of flow rules that you can add is actually limited by the FortiGate-6000 and 7000 internal switch hardware:
All FortiGate-6000F models support up to 256 flow rules.
All FortiGate-7000E models support up to 512 flow-rules.
A FortiGate-7000F with FIM-7941Fs supports up to 492 flow rules.
A FortiGate-7000F with FIM-7921Fs supports up to 52 flow rules.