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I was thinking about making it a bit easier to access the console port on a few switches deployed at work. Basically these switches are located top of rack above a KVM, and this makes accessing the console port very problematic since the KVM sticks out farther than the backside of the switch (where the console port is located).

I want to use a 1 port ethernet breakout box to extend the console port connection to right outside of the server rack so I can easily plug the console cable in when needed. I grabbed a rollover USB to serial cable and noticed something odd, the colors of the wires in the USB to serial cable are not standard at all. The color code goes Brown, Blue, Yellow, Green, Red, Purple, Orange, and Gray. No white-(insert color here) like I am used to with most ethernet cables. I need a pinout of how to map this console cable to a breakout box so I can access the console port without having to rip half of the rack down. Any ideas?

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    What standard do you expect them follow? IT'S NOT ETHERNET
    – Ricky
    Sep 12, 2023 at 23:01
  • In practice: Wiring cisco serial consoles straight into ethernet cable plant will usually work fine, maybe not always at 115200. Sep 13, 2023 at 23:32

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It's a serial port. If you want to extend it, wire it straight through. You can do it with an ethernet cable, but the twisted pairing can cause interference. (on short runs at low speeds, it won't matter) All you need are 3 pins: GND, TX, RX. On a cisco connector, GND is 4,5 (center pins), and TX/RX is 3,6 (the next pins). That makes reversing them easy... "rollover" cable.

(RS-232 serial is very old, mature technology. Cisco's use is just as old. All of this has been documented thousands of times for decades.)

Everything you didn't want to know about Cisco serial cables. (RS-232 anyway. There's another one for V.35)
https://www.cisco.com/c/en/us/support/docs/routers/7000-series-routers/12223-14.html

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  • Ok cool that's what I figured but I was getting hung up on if I should do straight or rollover.
    – Richie086
    Sep 12, 2023 at 23:44
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    ... and then there's that uber cool feature with AUX ports on Cisco routers. With a rollover cable attached between AUX and some another device's console port, you can use the AUX port to access the other device's console remotely; either from the router itself, or across the the network. Immensely useful if a failing device is half a day's travel time away... Sep 13, 2023 at 11:13
  • @Marc'netztier'Luethi - Never ever crossed my mind. Ingenious!
    – GCon
    Sep 13, 2023 at 13:35
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    @Gcon needs transport input telnet and no exec in the line aux ... config section, and then it's usually tcp/2001 giving access out through the AUX into the other device's console. Sep 13, 2023 at 13:52
  • SSH can be used, as well as many others. cisco.com/c/en/us/support/docs/dial-access/… (I don't remember what port ssh uses.) Also, show line to find your AUX port, it's not always "1"
    – Ricky
    Sep 13, 2023 at 17:16
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As mentioned console port is RS-232 serial port. Many manufacturers intentionally make those ports in RJ-45 form so you can plug regular UTP cables and make them distant, including use of structured cable system in buildings. If you use most-common default baud-rate 9600 bps then you can make this approx. 70 meters with no problem.

Not sure what your breakout box is but I think you should avoid using any, just use UTP cable.

One more option is to use access server or Ethernet-to-RS232 converter which are widely available.

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