How to use the FTDI USB serial cable to RJ45 adapter to connect to the console on Cisco/Juniper Switch Router Firewall in Linux Ubuntu Debian Redhat

This should work for most console ports of other manufacturers too.  It is a quick and simple method for emegencies or deploying a few appliances/devices in a non-standard environment or small environment. 

However, if this is a route thing, or the equipment is not physically close to you, it would be best to use some sort of "Terminal" server which is an IP connected switch with several serial ports built-in for this purpose.  Normally they accessible by web/ssh/telnet, so you don't have to worry about getting physical access to the device (eg. if it's in a communications room, datacenter or another place that is not convenient to physically access).

Step 1 - Just plugin the USB side and then connect to the console port of the device

The console port is often located at the back of the device, but some devices may have them at the front of the unit.  Also be careful that you don't connect it to the Management port of the device, as then this won't work and you won't receive any output to the terminal.

You should get output like this after plugging in the USB to RJ45 adapter:

[ 2113.427366] usb 1-1.2: new full-speed USB device number 24 using ehci-pci
[ 2113.542286] usb 1-1.2: New USB device found, idVendor=0403, idProduct=6001, bcdDevice= 6.00
[ 2113.542289] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2113.542292] usb 1-1.2: Product: FT232R USB UART
[ 2113.542294] usb 1-1.2: Manufacturer: FTDI
[ 2113.542295] usb 1-1.2: SerialNumber: A50285BI
[ 2113.544859] ftdi_sio 1-1.2:1.0: FTDI USB Serial Device converter detected
[ 2113.544901] usb 1-1.2: Detected FT232RL
[ 2113.545854] usb 1-1.2:
FTDI USB Serial Device converter now attached to ttyUSB0

Note the "attached to ttyUSB0" part, normally a standard serial cable would be available by deault on /dev/ttyS0, but with the USB adapter it will live on /dev/ttyUSB0

If you don't get the above output, confirm that the ftdi_sio kernel module is loaded.  If it's not there, you may need the following packages:

linux-modules-extra

Here is the easiest way to install the missing ftdi driver on Debian/Ubuntu/Mint

sudo apt install linux-modules-extra-`uname -r`

Step 2 - Connect to the console port on your device using screen/putty or other tool

One of the easiest tools to use is screen or putty, but any serial/terminal program will normally do the job.

screen /dev/ttyUSB0

Below is an example of consoling into a Juniper switch.

 


Tags:

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