cisco router default bootup process

[ Router Hardware Components ]

* ROM stores the Mini-IOS, the bootstrap program,ROMMON, and POST.
* Flash stores the IOS images.
* NVRAM stores the configuration files.
* RAM stores the active configuration, including
tables and buffers.

[ Router Bootup Process ]

* The configuration register and boot system commands can be used to

override the default router bootup behavior.

* Use the show version command to see the IOS version being used by

the router as well as the register value.

* If the fourth hexadecimal character of the configuration register

is 0x0, the router boots into ROMMON mode; if 0x1, the router boots

the Mini-IOS or the first file in flash if a Mini-IOS doesn´t exist;

if 0x2-0xF, the router uses the default boot sequence. The default

configuration register value is 0x2102. For the password recovery, it´s 0x2142.

Use the config-register IOS command to change this value.

* Here is the default bootup process: The bootstrap program examines

the configuration register to determine how to boot up. If it is

the default, the bootstrap program looks for boot system commands in

the configuration file in NVRAM. If none are found, it looks for

the IOS in flash. If no files are found in flash, the bootstrap

program generates a TFTP local broadcast to locate the IOS. If no

TFTP server is found, the bootstrap program loads the Mini-IOS in ROM.

If there is no Mini-IOS in ROM, the bootstrap program loads ROMMON.

* The System Configuration Dialog (setup script) will run when the

router boots up and there is no configuration file in NVRAM.

* Use the confreg command from ROMMON mode to change the configuration

register to 0x2142 to perform the password recovery process.


biOos