How-To: Connecting to a CISCO Router Console Port with USB and Linux

I was lucky enough to be loaned a couple of CISCO 1720 routers by my office today. Connecting to them was pretty straight forward.

What you will need:

1. A roll-over cable (aka Cisco Console Cable). These are usually RJ-45 on the router side and serial on the PC side.

2. If your computer doesn’t have a serial port (like mine) you can get a 9-pin D-sub serial to USB cable. I got the Gigaware cable from RadioShack for thirty dollars.

Get Connected:

The following worked for me with Hardy Heron installed on my MSI Wind.

1. Connect all the cables: USB — > Serial –> Crossover –> Console Port
2. Download and install Minicom: sudo apt-get install minicom
3. Make sure that the USB to serial cable is recognized. lsusb should list something like Bus 001 Device 002: ID 05ad:0fba Y.C. Cable U.S.A., Inc.
4. Type ls /dev/tty* to make sure /dev/ttyUSB0 or something similar is listed.

Update: In my search to reset the password to the router, I needed to send a break to the console. I was finally able to do this using GNU screen. Screen is easier than minicom, all you need to do is type screen /dev/ttyUSB0 instead of the remaining steps five through eight. I was then able to send my break using [meta-command]-B or [meta-command]-b (Not sure which it was).

5. Start minicom with minicom and hit CTRL-A and then O to open the options. (All commands in minicom start with CTRL-A, like GNU Screen).
6. Enter A to change the serial device setting to /dev/ttyUSB0 or whatever you found in step 4.
7. Select “Save setup as dfl”
8. Hit CTRL-A X to exit and then restart minicom, the port should be displayed as /dev/ttyUSB0
9. When it restarted all I had to do was hit enter to get the prompt of my CISCO 1720