what could be causing this problem?

You have successfully configured a router, but it prompts you to run Setup mode every time the router is
restarted. Based on the following output, what could be causing this problem?

A.
The router does not have sufficient flash memory.

B.
The configuration register is incorrect.

C.
The configuration file could not be found in NVRAM.

D.
The router could not locate a configuration file over the network.

Explanation:
The configuration register is incorrect. The configuration register value of 2142 is preventing the router from
loading the configuration file from NVRAM.
The router configuration register is used to control various aspects of the router boot sequence, and defaults to
a value of 2102. A configuration register of 2102 indicates that the router should boot normally, which consists
of loading the Internetwork Operating System (IOS) into RAM, then loading the saved configuration file from
Non-Volatile RAM (NVRAM) to configure the router.
Changing the configuration register to 2142 tells the router to bypass the saved configuration in NVRAM. This
causes the router to boot with a default running configuration, and prompt to run the Initial Configuration Dialog
(or Setup mode). Changing the configuration register to 2142 is necessary to perform password recovery or to
bypass any other aspect of a saved configuration that might be causing problems. After the situation is
resolved, the configuration register would then be changed back to the default of 2102 with the following
command:
Router(config)# config-register 0x2102
The router is successfully loading the IOS from flash memory, so insufficient flash memory is an incorrect
answer.
The configuration register is instructing the router to bypass the configuration file in NVRAM, so it is incorrect to
state that the configuration file could not be found in NVRAM.
The configuration register is instructing the router to bypass the configuration file in NVRAM, so it is incorrect to
state that the router could not locate a configuration file over the network.
Objective:
Infrastructure Management
Sub-Objective:
Use Cisco IOS tools to troubleshoot and resolve problems

Cisco > Product Support > Routers > Cisco 10000 Series Routers > Troubleshoot and Alerts > Troubleshooting
TechNotes > Use of the Configuration Register on All Cisco Routers > Document ID: 50421
Cisco > Cisco IOS Configuration Fundamentals Command Reference > config-register