Unless you are doing this to resolve an outage, plan this firmware installation because there will be an outage from when you reboot the FortiGate unit until it restarts with the new firmware.

Configure the terminal client communication parameters to 8 bits, no parity, 1 stop bit (8-n-1), 9600 baud. (For FortiGate-300 use 115,000 baud.)

To load firmware

1. Connect the terminal to the FortiGate unit using the null modem cable.
2. Connect the PC running the TFTP server to the FortiGate unit.
   On models 1000 and higher, connect to port 1. On model 500A, connect to the LAN interface. On other models, connect to the Internal interface if there is one, otherwise connect to port 1. 
3. Turn the power off and then on at the Fortigate unit.
4. When the console displays "Press any key to display configuration menu..." press the spacebar or any other key.
5. If the menu includes Format boot device [F] press F and wait for the device formatting to complete.
6. At the console, press G to start firmware download.
   The console displays
   Enter TFTP server address [192.168.1.168]:
7. Type the IP address of the computer running the TFTP server and press Enter.
   The console displays
   Enter Local Address [192.168.1.188]:
8. Type an unused IP address that is on the same subnet as the TFTP server and press Enter.
   The console displays
   Enter File Name [image.out]:
9. Type the firmware image filename and press Enter.
   The console periodically displays a “#” to show download progress. When the download is complete, it displays a messsage similar to Save as Default firmware/Run image without saving:[D/R]
10. Press D.
    The FortiGate unit installs the new firmware image and restarts. The installation might take a few minutes to complete.