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Cisco Console via aux Port

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.

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