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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 Beam Aug 15 '18 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. – Marc 'netztier' Luethi Aug 16 '18 at 10:59
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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.

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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. – hypersonics Aug 15 '18 at 9:31

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