Which Cisco IOS command allows you to change the setting of the configuration register?

A.
boot config

B.
configuration-register edit

C.
config-register

D.
edit configuration-register

Explanation:
The config-register command is used to change the setting of the configuration register. The configuration register has the boot field setting, which specifies the
order in which the router should look for bootstrap information. The router contains a 16-bit software register, which is stored in the non-volatile random access
memory (NVRAM). The config-register command is used to modify the default configuration register. The most common use of changing this register is to instruct
the router to ignore the stored configuration file and boot as a new router with no configuration. This process is normally used when a router has a password that is
not known and must be reset. For security purposes, this procedure can only be performed from the console connection, which means it requires physical access to
the router.

Normally the setting of this register is 0x2102, which tells the router to look for a configuration file. If the file exists, it will use it. If none exists, the router will boot into
ROM and present the user with a menu-based setup. This would be the default behavior for a new router as well.
To view the value of the configuration register, use the show version command as displayed below. The register setting can be seen at the bottom of the output in
bold.

Configuration register is 0x2102
To change this setting would require issuing these commands, followed by a restart:
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#config
Router(config)#config-register 0x2142
By setting register to 0x2142, the router will ignore a configuration file at reboot if it exists. The router will then enter setup mode and prompt for you to enter initial
system configuration information, as would happen with a new router. This enables the user to bypass an unknown password, since the password is contained in
the file.
The boot config command is incorrect because this command is used to set the device where the configuration file is located (flash, slot, etc.) and file name for the
configuration file, which helps the router to configure itself during startup.

The configuration-register edit command and the edit configuration-register commands are incorrect because they are not valid Cisco IOS commands.
Objective:
Infrastructure Management
Sub-Objective:
Perform device maintenance

Cisco > Support > Routers > Cisco 10000 Series Routers > Troubleshoot and Alerts > Troubleshooting TechNotes > Use of the Configuration Register on All Cisco
Routers > Document ID: 50421