FortiGate 80F – Serial console displays garbled characters on two appliances

Hello,

I’m experiencing an issue with serial console access on FortiGate 80F appliances, where the console displays continuous garbled and unreadable characters.

This issue has occurred on more than one FortiGate 80F.

Environment

Model: FortiGate 80F
FortiOS version: 7.4.8
Access method: Serial console (RJ45)
Terminal software: PuTTY (Windows)

Serial settings tested

All combinations below were tested, including during cold boot:

9600, 57600 and 115200 baud
Data bits: 8
Parity: None
Stop bits: 1
Flow control: None

In all cases, the console outputs unreadable characters continuously.

Troubleshooting already performed:

Tested multiple baud rates
Tested different serial cables
Tested different USB-to-Serial adapters
Tested on different computers
Issue reproduced on multiple FortiGate 80F units
Tested console access during boot sequence