Cisco Certified Network Associate (CCNA) Practice Exam 2026 - Free CCNA Practice Questions and Study Guide

The command used to change the configuration register back to the default value on a router is indeed "config-register 0x2102." The configuration register is a 16-bit value that determines how a Cisco router boots and operates. The default value, 0x2102, instructs the router to load the operating system from Flash memory and to ignore the configuration stored in NVRAM if the router is in a mode that requires the device to load a system image.

Setting the configuration register to this value allows the router to boot normally, utilizing the saved configurations in NVRAM unless specifically overridden by boot commands, making it essential for troubleshooting and recovery scenarios. While alternative commands may sound similar, they are not valid Cisco IOS commands, so they would not produce the desired outcome. Properly setting the configuration register is crucial for maintaining system integrity and functionality in a Cisco networking environment.