Please do not follow these steps if you are a new to Routers, as this can damage the IOS or any physical interface of the router.
1.Connect a computer to the router’s Console port using the Console cable that came with your router (it is usually flat and light blue).
Use these terminal settings:
* 9600 baud rate
* No parity
* 8 data bits
* 1 stop bit
* No flow control
2.Turn the router off using the power switch and turn it back on.
3.Once text starts popping up on the screen, send the break command CTRL + B or CTRL +BREAK (sometimes it is CTRL +X). This will abort the boot and present you with a rommon 1> prompt
4.From the new prompt you need to change the configuration register using the following command: confreg 0×2142
5.If you are using an older model of router you may need to enter o/r 0×2142
6.Now you need to recycle the router with the reset command.
7.If you used the o/r command then reset the router with the I command
8.Once the router finishes restarting you will find that there are no passwords to deal with, so you can enter enabled mode carte blanche.
9.Once in enabled mode enter this: copy start run. This will copy the startup config to the running config.
10.Now, go into configuration mode with the config t command
11.Once there enter the new password with the enable secret password command (i.e. enable secret admin).
12.Now set the configuration register back to normal with this command: confreg 0×2102
13.Exit config mode and enter the command copy run start to copy the new configuration to ram.
14.Now it is time to reload your router
15.Once the router is back up you need to configure all of your interfaces with the no shutdown command or they will not work.