Password resetting on cisco router.

Note: After doing all these steps you will lose your all configuration so make sure you have backup of your configuration.

Start the router and interrupt the router boot process by pressing Ctrl+break OR Ctrl+pause key after performing this step you will see the following prompt on router. 

Rommon1>

The Purpose of the Configuration Register

The configuration register can be used to change router behavior in several ways, such as:

• how the router boots (into ROMmon, NetBoot)
• options while booting (ignore configuration, disable boot messages)
• console speed (baud rate for a terminal emulation session)

You have to change the router configuration register setting by executing following command.

Rommon1>confreg 0x2142

Note: The factory-default setting for the configuration register is 0x2102. This indicates that the router should attempt to load a Cisco IOS software image from Flash memory and load the startup configuration with a console speed of 9600 baud.

By changing this value you can reset the router password, by setting confreg to 0x2142 router will not look into NVRAM for startup config.

Rommon2>reset

Now login to the router and change your password. You will also have to change configuration register number to default otherwise router will always enter into setup mode by ignoring NVRAM

Router>enable

Router#show version

You can check the configuration register number by using this command.

Router#configure terminal

Router(config)#enable secret test123

Router(config)#config-register 0x2102

Router(config)#do write

Now we are done !!