Technical Tip: How to disable the Forward Error Correction (FEC) feature on FortiGate ULL ports

FortiGate: This issue only applies to devices with ULL ports after 7.2.9.  FortiGate platforms with ultra-low-latency (ULL) ports, such as the 600F and 901G models, may experience a 'status down' issue on active ULL ports under specific conditions. This change results from a fix in version 7.2.9 addressing how FEC (Forward Error Correction) operates on ULL ports. In 7.2.9, Forward Error Correction is now active on FortiGate, which can cause a mismatch if the connected switch has FEC disabled.

Condition/Context

• FEC is enabled on the FortiGate ULL port.
• FEC is disabled on the connecting switch.

To disable FEC on the ULL port, use the following commands:

config system interface
    edit <ULL port>
        set forward-error-correction disable
    next
end

To verify the change was made, run the following:

show system interface <port>

To monitor the ports for current status:

get system status

get system interface

show system interface <port>

get hardware nic

diagnose hardware deviceinfo nic <port>

To revert disabling this feature:

set forward-error-correction enable

Disabling FEC can increase error rates or data loss.