You need to use your Cisco through the console, like an enable secret recovery, but you forgot your usb-serial dongle. If you have another Cisco near by with remote access you are safe!
Preparation
Start connecting a Cisco console cable (cross over cable) from the console port of the router (routerc) to the auxiliary port of the helpful router (routerh).
After remotely accessing routerh configure it’s aux line
routerh#conf t
Enter configuration commands, one per line. End with CNTL/Z.
routerh(config)#line aux 0
routerh(config-line)# transport input telnet
routerh(config-line)#^Z
routerh#
Using the console
We need to know the line number of the AUX port and the IP address of this routerh
routerh#sh line
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
0 CTY - - - - - 0 0 0/0 -
1 AUX 9600/9600 - - - - - 13 21 0/0 -
* 2 VTY - - - - 5 202 0 0/0 -
3 VTY - - - - 5 1 0 0/0 -
4 VTY - - - - 5 4358 0 0/0 -
5 VTY - - - - 5 125 0 0/0 -
6 VTY - - - - 5 1 0 0/0 -
routerh#
It shows the aux port is on line 1. Our IP address is 192.168.1.1
To access the console you have to telnet your local IP address at port 2000 plus the line number:
routerh#telnet 192.168.1.1 2001
Trying 192.168.1.1, 2001 ... Open
routerh line 1
User Access Verification
Username: biafra
Password:
[ENTER]
routerc line 1
User Access Verification
Username: biafra
Password:
routerc#
And you are now using the console of routerc. Please note that you may have no console access restrictions as it’s shown here because of AAA.
Suspending and Disconnecting
You can get back to routerh with ctrl-6 x (or ctrl-shift-6 x).
routerh#sh users
Line User Host(s) Idle Location
1 aux 0 biafra idle 00:00:13 192.168.1.1
* 2 vty 0 biafra 192.168.1.1 00:00:09 10.0.0.10
Interface User Mode Idle Peer Address
routerh#
Just hitting enter or entering the session number you are connected again to the remote console.
To disconnect just check the aux line with sh users and
routerh#clear line 1
[confirm]
[OK]
routerh#
[Resuming connection 1 to 192.168.1.1 ... ]
[Connection to 192.168.1.1 closed by foreign host]
routerh#
routerh#sh users
Line User Host(s) Idle Location
* 2 vty 0 biafra 192.168.1.1 00:00:14 10.0.0.10
Interface User Mode Idle Peer Address
routerh#
To remember
Configure the aux port and suspend the console with ctrl-6 x.
