Cisco Exam 100-490 Topic 10 Question 47 Discussion

The configuration register on Cisco devices controls how the device boots up. By changing the configuration register to 0x2142, you instruct the router to bypass the startup configuration file stored in NVRAM. This is crucial in the password recovery process because the passwords are stored in this configuration file.

Procedure for Password Recovery:

1. Break the boot sequence: Power cycle the router (turn off/on). During the boot process, send a 'Break' signal to get into ROMmon mode.

2. Change the configuration register: In ROMmon mode, type confreg 0x2142 and reload the router.

3. Boot without startup-config: The router will boot up, ignoring the saved startup configuration, allowing you to enter privileged EXEC mode without a password.

4. Change the password: Access configuration mode (configure terminal), and change the passwords as needed (enable password, enable secret, etc.).

5. Reset the configuration register: Set the configuration register back to its original value (usually 0x2102).

6. Save changes: Save the new configuration with copy running-config startup-config.