How to connect to a Cisco device using the serial port on Linux

Using the serial port is still necessary to manage some devices, when it is reseted to factory defaults. It could be also a security choice…

Nowadays many computers – and especially laptops don’t have anymore a built-in serial port. Not a problem, there are many cheap serial-usb converters like this.

As an alternative to the Hyperterminal of Microsoft, there is Minicom on Linux.

It is very easy to install and configure :

$ apt-get install minicom lrzsz

Before going further, you need to know what is the corresponding Linux device for the port where you plugged the router. As I used an usb adapter, my device was /dev/ttyUSB0. Otherwise, it will probably be one of the /dev/ttyS* devices.
Checking the dmesg output while you plug the device will give you the right device to use.

Now start minicom this way to edit the configuration :

$ minicom -s

In the menu, select Serial Port Configuration and :

  • press A and update the serial port path with the one you found in dmesg
  • press E and then C to change the speed to 9600
  • press F to switch off the hardware flow control
  • select Save the configuration as… and name it as, let’s say, “cisco”

You should be able to connect right now. Next time, just start Minicom like this :

$ minicom cisco

That’s it !