Cisco reverse telnet (AUX -> CON)

Let me jot this down before I forget it again, I’ve looked this up so often 😉
First we hook up the CON port of the borked device with the AUX port of a working router (the normal Cisco console cable with RJ45 connectors on both ends). Then we go to the router and configure it’s AUX port with these settings:

# conf t
# line aux 0
(config-line)# modem InOut
(config-line)# transport preferred all
(config-line)# transport input all
(config-line)# transport output all
(config-line)# stopbits 1
(config-line)# end

The router has to have a loopback address and it must be up (duh). Now we have to find out which port we are going to have to telnet to. Do a show line from the enable mode, the output should look something like this:

Tty Typ Tx/Rx A Modem
0 CTY – –
* 97 AUX 9600/9600 – inout
* 98 VTY – –

Our line is number 97, telnet to the loopback address and port 2000+our line. If our loopback had the IP the command would be telnet 2097