Cisco access ROMMON mode with reverse telnet aux.

If you are using putty with serial port. To access rommon mode press

Ctrl + Shift + Break or Pause.

And if you are using Terra Term with serial port press

Alt + B

Configure aux 0 for reverse telnet.

conf term
line aux 0
 modem InOut
 transport input all
 exit
!

How to find line number for aux 0

R01#show line
   Tty Line Typ     Tx/Rx    A Modem  Roty AccO AccI  Uses  Noise Overruns  Int
      0    0 CTY              -    -      -    -    -     0      0    0/0      -
*     1    1 AUX   9600/9600  - inout     -    -    -     0      0    0/0      -
*   514  514 VTY              -    -      -    -   50     1      0    0/0      -
    515  515 VTY              -    -      -    -   50     0      0    0/0      -
!

Now that found line number for aux 0 is line number 1.
IP address of the router 2000 + line number 1
Is telnet 10.1.1.1 2001

R01#telnet 10.1.1.1 2001
Trying 10.1.1.1, 2001 ...
% Connection refused by remote host

R01#clear line 1
[confirm]
 [OK]
R01#telnet 10.1.1.1 2001
Trying 10.1.1.1, 2001 ... Open

User Access Verification

Username: admin
Password:
PPPOE#
PPPOE#
PPPOE#


Then what to do with reverse telnet how to access rommon mode ?

( Ctrl + Shift + 6 ) release and then press B

System Bootstrap, Version 12.4(13r)T11, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 2009 by cisco Systems, Inc.

Initializing memory for ECC
.
c2811 platform with 262144 Kbytes of main memory
Main memory is configured to 64 bit mode with ECC enabled


Upgrade ROMMON initialized
PC = 0xbfcd0d54, Cause = 0x2000, Status Reg = 0x3040a803

monitor: command "boot" aborted due to user interrupt
rommon 1 >
rommon 1 >
rommon 1 >
rommon 1 > confreg 0x2142


You must reset or power cycle for new config to take effect
rommon 2 > reset

After reset.


Router>en
Router#copy start running-config
Destination filename [running-config]?

2991 bytes copied in 12.400 secs (241 bytes/sec)
PPPOE#
PPPOE#conf term
Enter configuration commands, one per line.  End with CNTL/Z.
PPPOE(config)#config 0x2102
PPPOE(config)#end
PPPOE#
*Apr 30 04:55:47.419: %SYS-5-CONFIG_I: Configured from console by console
PPPOE#show version

Configuration register is 0x2142 (will be 0x2102 at next reload)

PPPOE#

Then to exit reverse telnet.

( Ctrl + Shift + 6) release and then press X

https://supportforums.cisco.com/discussion/11390416/how-do-you-send-break-putty-cisco-2600-terminal-server

http://www.cisco.com/c/en/us/td/docs/ios/termserv/configuration/guide/15-mt/tsv-15-MT-book/tsv_dialin_term_svcs.html

https://networklessons.com/network-services/cisco-terminal-server-configuration-example/

http://ciscofaq.blogspot.com/2005/05/how-to-i-reverse-telnet-out-my-aux.html

https://supportforums.cisco.com/discussion/10680346/me-3400-password-recovery

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