Bug ID 673974: agetty auto detects parity on console port incorrectly

Last Modified: Oct 06, 2020

Bug Tracker

Affected Product:  See more info
BIG-IP TMOS(all modules)

Known Affected Versions:
12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3,,,,,,,, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1

Fixed In:
13.1.0, 12.1.4

Opened: Jul 13, 2017
Severity: 3-Major
Related AskF5 Article:


With a BIG-IP system configured for a console baud rate that is different from the baud rate of the serial terminal that is plugged in to the console port, he system returns garbled characters on the screen. Changing the terminal setting to match the console baud rate has no effect after that: the BIG-IP system continues to send garbage.


The parity detection code selects the wrong setting, leaving the console port unusable until reboot of the BIG-IP system, or after killing and restarting agetty.


BIG-IP system with a console at certain baud rate. -- Plug in a serial terminal with a different baud rate. -- Press enter several times.


To recover from this condition, log on to the BIG-IP system via ssh, force parity off, and kill the agetty process (assuming the console is not logged in, and is therefore running agetty). via ssh: # stty -F /dev/ttyS0 -parenb ; killall agetty However, this is not an ideal workaround, as a frequent reason to use the serial console is lack of network access to the device. In that situation, you can log on by setting the terminal to Mark parity (8 data bits, Mark parity, 1 stop bit). Note: There is no way to mitigate the issue from the console connection itself, as agetty doesn't run while the console is logged in. You can also reboot the BIG-IP system, reset the terminal speed on the laptop to match the console speed set on the BIG-IP system, and reconnect the laptop.

Fix Information

This issue has been corrected.

Behavior Change