.Which Cisco IOS command allows you to change the setting of the configuration register?
A. boot config
B. configuration-register edit
D. edit configuration-register
Correct Answer: C
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:
Enter configuration commands, one per line. End with CNTL/Z.
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.
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