Got a used Cisco Catalyst 2960G-24TC-L switch for studying networking and having a fundamental issue. As I new to networking, I'm trying to figure out what type of cable I need to use for connecting between the switch and my laptop.

The switch has an RJ45 type for a console port and I plugged a CAT5 cable into it and on the other end, I have a RJ45 to USB. Connected the USB end to my laptop. I'm running a CentOS 7 and tried

demsg /dev | grep tty

and I get a ttyS0 as the output. Further, I tried,

screen /dev/ttyS0 9600

I get a blank screen with a flashing cursor. Nothing happens when I hit enter.

Any idea what might be going on here? Should I be going with RJ45 console to DB9 and then DB9 to USB?

  • (0) RJ45 to USB serial adapter??? (1) linux usb serial is /dev/ttyUSB# (2) the 2960's have a usb console as well that linux should detect -- I've never tried.
    – Ricky
    Commented Aug 15, 2018 at 16:58
  • Recent 2960X series may have an USB console, but a venerable 2960G-24-TC-L? That'd be somewhat of a surprise. Commented Aug 16, 2018 at 10:59

2 Answers 2


The console port on Cisco devices might have RJ45 (8p8c) form factor, but it is not Ethernet, but RS-232 serial.

Usually, the Cisco device comes with a RJ45(serial)-to-DB9 console cable (light blue, flat ribbon cable, not twisted pair), and you would use an USB-to-DB9 RS232 converter at the computer end, as DB9 serial ports have become rare on computers.

USB-to-RJ45(serial) adapters (in the form of a 1.5-2m cable) have also become available, eliminating the DB9 interface (re)conversion altogether.

The RJ45 section of such cabling may be extended using a straight Cat5/Cat6 patch cables.

Some recent Cisco models have an USB-to-Serial converter built-in, and they offer a mini-USB-5pin port, to which you can connect a computer directly.


You can't use RJ45 to USB for Console port (Because there isn't a convertor!). You should buy a USB to RJ45 Rollover Console Cable to connect to Cisco Console line.

Also, I tested it. You can buy and put RS232 Serial Cable to RS-232 Serial to USB and connected to cisco consoe line.

  • 1
    Thank you. I have ordered a RJ45 to DB9 (RD232) and DB9 (RS232) to USB. Commented Aug 15, 2018 at 9:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.