Password- and configuration-recovery for Cisco IOS router

You bought a used Cisco router at eBay configured with a password? You loose your password but still need the current configuration? No Problem! You can easily reset the configuration/passwords.

You need to connect to the serial port of the Cisco router. I’m using always a USB-RS232-serial-adapter and PuTTY for this. To boot your router in to the rommon u need to power off and on the device and send break signals over the COM port (right-click on the icon):

Send the break-signals periodically until you see the rommon shell. Now you need to configure the configuration-register to 0x2142 and reset the router:

System Bootstrap, Version 12.3(8r)YI4, RELEASE SOFTWARE
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 2006 by cisco Systems, Inc.

C870 series (Board ID: 6-148) platform with 131072 Kbytes of main memory

rommon 1 > confreg 0x2142

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

Changing the configuration-register to 0x2142 will ignore the loading of the startup-configuration after booting the IOS image. After booting, you will see the installation wizard:

         — System Configuration Dialog —

Would you like to enter the initial configuration dialog? [yes/no]: no

You are now logged in and can switch back to the standard configuration-register 0x2102:

Router(config)#config-register 0x2102

with show startup-configuration you can watch the saved configuration. You can also see all the passwords within the configuration (for example user-passwords or the presharedkeys for VPN tunnels). If the configuration contains the password-encryption command you can decrypt type 7 passwords. I puplished a tool on my site to decrypt those passwords: Cisco Password Decrypter

If you want to make the startup-configuration active with your own passwords (username, enable secret, etc.) you can load the startup-configuration to the running-configuration and configure the new passwords:

Router#copy startup-config running-config
Router#configure terminal
Router(config)#username cisco password cisco
Router(config)#enable secret cisco
Router(config)#end
Router#copy running-config startup-config
or
Router#write memory
Router#reload

After the reload you can test your (hopefully successful) login! Happy Hacking! ^^

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