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Reverse Telnet Aux Port to Cisco 300 Series Switch

The Cisco line of 300 switches provides you with a serial cable (DB-9 to DB-9) to connect to the console of the switch. Not sure if it’s a straight or null cable, but in either case here’s how to configure a Cisco router to reverse telnet using the aux port and into the console port of the switch.

First off, the route needs this config on the aux port.
line aux 0
modem InOut
transport input all
transport output all
stopbits 1
speed 115200

(speed is important as the 300 switches operate at this speed by default, but the aux port runs at 9600)

Then use a blue Cisco console cable (the one with RJ-45 on one end and DB-9 on the other) and roll it over by reversing the pins. I simply cut off the RJ-45 end and put another one in by flipping the connector.

Here’s some info on the Aux port and what a rolled cable is in case you need it.

After that you can now connect to the switch. Here’s some info on how to reverse telnet, my goal is simply to show you the cabling and aux config that worked for me.

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