Technical Tip: How to fix a half-duplex port after a reboot or port bounce

Whenever a port runs at whichever speed and full duplex,  FortiGate can be reloaded under any circumstance or simply bounced. But the port comes back on in half-duplex, as can be seen in the image below by using the following diagnose command:

diagnose hardware deviceinfo nic <desired port>

For example, in this case:

diagnose hardware deviceinfo nic internal2

If this happens, a simple bounce or configure port in full-duplex won't be enough; hence, to fix this, follow up below steps:

1. Turn the port down:

config system interface
    edit <port name>

        set status down

end

2. Connect a PC or a Layer 2 switch to have a port able to be detected and avoid generating any DHCP.
3. Choose speed and duplexing according to technical need.

---------Speed--------------
100full ---> 100M Full
100half ---> 100M half
10full ---> 10M Full
10half ---> 10M half

4. Enable the port with speed and duplex:

config system interface
    edit <port name>

        set speed 1000full

        set status up

end

After executing the above steps, the port will come up with full duplex as in the image below:

Note:

Following implementation of all changes, the port shows physical connectivity but remains administratively down, indicating a hardware fault. Initiation of the RMA process is required.

Related articles:
Technical Tip: Changing the speed of a FortiGate interface

Technical Tip: How to adjust the Maximum Transmission Unit (MTU) value