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TUCoPS :: Password Security :: pwrcisco.txt

Password Recovery Techniques for Cisco Routers




Password Recovery Techniques

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Introduction

This document will explain several password recovery techniques for Cisco
routers. You can perform password recovery on most of the platforms without
changing hardware jumpers, but all platforms require the router to be
reloaded. Password recovery can only be done from the console port
physically attached to the router.

There are three ways to restore enable access to a router when the password
is lost. You can VIEW the password, CHANGE the password, or ERASE the
configuration and start over as if the box was new.

Each procedure follows these basic steps:

  1. Configure the router to boot up without reading the configuration
     memory (NVRAM). This is sometimes called the test system mode.

  2. Reboot the system.

  3. Access enable mode (which can be done without a password if you are in
     test system mode).

  4. VIEW or CHANGE the password, or ERASE the configuration.

  5. Reconfigure the router to boot up and read the NVRAM as it normally
     does.

  6. Reboot the system.

     NOTE: Some password recovery requires that a terminal issues a
     Break signal; you must be familiar with how your terminal or PC
     terminal emulator issues this signal. For example, in ProComm,
     the keys Alt-B will by default generate the Break signal, and in
     Windows Terminal you press Break or CTRL-Break. Windows Terminal
     also allows you to define a function key as BREAK. From the
     terminal window, select Function Keys and define one as break by
     filling in the characters ^$B (Shift 6, Shift 4, and Capital B).

The following six sections contain detailed instructions for specific Cisco
routers. Locate your router in the section headings to determine which
technique to use.

Technique #1

All Cisco 2000 Series, 2500 Series, 3000 Series, 680x0-Based 4000 Series,
7000 Series Running 10.0 or Later in ROMs, IGS Series Running 9.1 or Later
in ROMs

This technique can be used on the 7000 and 7010 only if the router has 10.0
ROMs installed on the RP card. It may be booting Flash 10.0 software, but
it needs the actual ROMs on the processor card as well.

  1. Attach a terminal or PC with terminal emulation to the console port of
     the router.

  2. Type "show version" and record the setting of the configuration
     register. It is usually 0x2102 or 0x102.

  3. Power the router down, then up.

  4. Press the Break key on the terminal within 60 seconds of the power up.
     You will see the > prompt with no router name. If you don't, the
     terminal is not sending the correct Break signal. In that case, check
     the terminal or terminal emulation setup.

  5. Type "o/r0x42" at the > prompt to boot from Flash or "o/r 0x41" to
     boot from the boot ROMs. Note that this is the letter "o," not the
     numeral zero. If you have Flash and it is intact, 0x42 is the best
     setting. Use 0x41 only if the Flash is erased or not installed.

          NOTE: If you use 0x41, you can only view or erase the
          configuration. You cannot change the password.

  6. Type "i" at the > prompt. The router will reboot but will ignore its
     saved configuration.

  7. Answer "no" to all the setup questions.

  8. Type "enable" at the "Router>" prompt. You'll be in enable mode and
     see the "Router#" prompt.

  9. Choose one of these three options:

        o To VIEW the password type "show config."
        o To CHANGE the password (in case it is encrypted, for example):
          a. Type "config mem" to copy the NVRAM into memory.
          b. Type "config term" and make the changes to the configuration.

                   conf t
                   enable password password
                   ctrl-z

          c. Type "write mem" to commit the changes.
        o To ERASE the config, type "write erase.

 10. Type "config term" at the prompt.

 11. Type "config-register 0x2102," or whatever value you recorded in step
     2.

 12. Hit Ctrl-Z to quit from editor.

 13. Type "reload" at the prompt. You do not need to write memory.

Technique #2

Cisco 1003, 4500, or IDT Orion-Based Routers

  1. Attach a terminal or PC with terminal emulation to the console port of
     the router.

  2. Type "show version" and record the setting of the configuration
     register. It is usually 0x2102 or 0x102.

  3. Power the router down, then up.

  4. Press the Break key on the terminal within 60 seconds of the power up.
     You will see the "rommon>" prompt. If you don't, the terminal is not
     sending the correct Break signal. In that case, check the terminal or
     terminal emulation setup.

  5. Type "confreg" at the "rommon>" prompt.

  6. Answer "y" to the "Do you wish to change configuration[y/n]?" prompt.

  7. Answer "n" to all of the questions that appear until you reach the
     "ignore system config info[y/n]?" prompt. Answer "y."

  8. Answer "n" to the remaining questions until you reach the "change boot
     characteristics[y/n]?" prompt. Answer "y."

  9. At the "enter to boot:" prompt, type "2" followed by a carriage
     return. If Flash is erased, type "1." If all Flash is erased, the 4500
     must be returned to Cisco for service.

          NOTE: If you use "1," you can only view or erase the
          configuration. You cannot change the password.

 10. A configuration summary is printed. Answer "n" to the "Do you wish to
     change configuration[y/n]?" prompt.

 11. Type "reset" at the "rommon>" prompt, or power cycle your 4500 or
     7500.

 12. Once it boots up, answer "no" to all the Setup questions.

 13. Type "enable" at the "Router>" prompt. You'll be in enable mode and
     see the "Router#" prompt.

 14. Choose one of these three options:

        o To VIEW the password type "show config."
        o To CHANGE the password (in case it is encrypted, for example):
          a. Type "config mem" to copy the NVRAM into memory.
          b. Type "config term" and make the changes to the configuration.

                   conf t
                   enable password password
                   ctrl-z

          c. Type "write mem" to commit the changes.
        o To ERASE the config, type "write erase."

 15. Type "config term" at the prompt.

 16. Type "config-register 0x2102" or whatever value you recorded in step
     2.

 17. Hit Ctrl-Z to quit from the editor.

 18. Type "reload" at the prompt. You do not need to write memory.

Technique #3

IGS Routers Running Software Earlier Than 9.1

IGS routers have a bank of DIP switches on the rear panel. If they are
running software earlier than 9.1, then these switches are used for
password recovery.

  1. Attach a terminal or PC with terminal emulation to the console port of
     the router.

  2. Power the router down.

  3. Record the settings of the switches on the rear panel.

  4. Set switch 7 ON (or down).

  5. Set switches 0-3 OFF (or up).

  6. Power the router up. It will boot up to the > prompt.

  7. Type "b" at the > prompt. The router is in test-system mode.

  8. Press return until the "Test-System>" prompt appears.

  9. Type "enable" at the prompt. You'll be in enable mode and see the
     "Test-System#" prompt.

 10. Choose one of these three options:

        o To VIEW the password type "show config."
        o To CHANGE the password (in case it is encrypted, for example):
          a. Type "config mem" to copy the NVRAM into memory.
          b. Type "config term" and make the changes to the configuration.

                   conf t
                   enable password password
                   ctrl-z

          c. Type "write mem" to commit the changes.
        o To ERASE the config, type "write erase".

 11. Restore the switch setting to those recorded in step 3.

 12. Reboot the router.

Technique #4

CGS, MGS, AGS, AGS+, 70x0 Running ROMs Lower Than 10.0

  1. Attach a terminal or PC with terminal emulation to the console port of
     the router.

  2. Power the router down.

  3. Remove the processor card (CSC/2 or CSC/3 or CSC/4 on AGS/CGS/MGS, or
     RP on a 70x0).

  4. Change the hardware register from bit position 0 (or 1) to position
     15.

  5. Re-insert the processor card.

  6. Power the router up.

  7. Press "b" at the > prompt or "b flash" if you have Flash memory
     installed.

  8. Press return until the "Test-System>" prompt appears.

  9. Type "enable" at the prompt. You'll be in enable mode and see the
     "Test-System#" prompt.

 10. Choose one of these three options:

        o To VIEW the password type "show config."
        o To CHANGE the password (in case it is encrypted, for example):
          a. Type "config mem" to copy the NVRAM into memory.
          b. Type "config term" and make the changes to the configuration.

                   conf t
                   enable password password
                   ctrl-z
               c. Type "write mem" to commit the changes.

        o To ERASE the config, type "write erase."

 11. Power the router down.

 12. Remove the processor card and return the jumper on pin 15 to its
     original position.

 13. Power the router up.

Technique #5

500-CS Communication Servers

The password cannot be recovered from the 500-CS since it does not have a
console port. Your only option is to erase the configuration.

  1. Power the router off by unplugging it.

  2. Depress and hold the DEFAULT button on the front of the chassis.

  3. Power the router back on.

  4. Watch the OK and LAN LEDs. They will blink on, and then off.

  5. When they blink off (after about 15 seconds), release the DEFAULT
     button.

  6. In 2-10 minutes, the 500-CS will enter setup mode as if it was factory
     new.

  7. Configure the router.

You could also recover a password on a 500 by holding the DEFAULT button
down for 30-45 seconds. The system will then be in test mode, and you can
follow the normal procedure for password recovery. See the earlier sections
for details.

Technique #6

Cisco 1020

You must call the Cisco TAC to recover Cisco 1020 passwords. The 1020 will
issue a password override challenge that can only be interpreted by TAC
personnel.

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Posted: Thu Aug 17 11:57:44 PDT 1995



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