With "configuration register", we can configure what the router will do at the next reboot.


To see what is the actual setting of your routers configuration register, use router#show version

To change the configuration register, use the following command in global config mode:
Router(config)#config-register 0x2142

For CCNA exam, you need to know two configuration register settings. These are:

0x2102 is the factory-default configuration register value.
0x2142 boots from flash without using NVRAM contents good for password recovery.

When the config. register is set to 2142, the router will start in setup-mode,
where you can interactive select some options.
The "normal" config. register is 2102.