Cisco Router Components

Bootstrap
Brings up the router during initialization

POST
Checks basic functionality; hardware & interfaces

ROM monitor
Manufacturing testing & troubleshooting

Mini-IOS
Loads Cisco IOS into flash memory

RAM
Holds packet buffers, routing tables, & s/w
Stores running-config

ROM
Starts & maintains the router

Flash Memory
Holds Cisco IOS
Not erased when the router is reloaded

NVRAM
Holds router (& switch) configurations
Not erased when the router is reloaded

Configuration Register
Controls how the router boots up


Boot Sequence

1: Router performs a POST

2: Bootstrap looks for & loads the Cisco IOS

3: IOS software looks for a valid configuration file

4: Startup-config file (from NVRAM) is loaded
If startup-config file is not found, the router will start the setup mode


Configuration Registers

Configuration Meanings


Boot Field Meanings


Checking the Register Value

Changing the Configuration Register

• Force the system into the ROM monitor mode

• Select a boot source & default boot filename

• Enable or disable the Break function

• Set the console terminal baud rate

• Load operating software from ROM

• Enable booting from a TFTP server

Changing the Configuration Register


Recovering Passwords

1: Boot the router & interrupt the boot sequence by performing a break
2: Change the configuration register to turn on bit 6 (0x2142)
3: Reload the router
4: Enter the privileged mode
5: Copy the startup-config to running-config
6: Change the password
7: Reset the configuration register to the default value
8: Reload the router


Recovering Passwords:

1: Boot the router & interrupt the boot sequence by performing a break using the Ctrl+Break key combination.

You may need to upgrade your version of hyper-terminal in order for this to work successfully.

2: Change the configuration register to turn on bit 6 (0x2142)
rommon>confreg 0x2142
You must reset or power cycle for new config to take effect

3: Reload the router
Type reset
The router will reload & ask if you want to enter setup mode
Answer NO

4: Enter the privileged mode
Router>enable
Router#

5: Copy the startup-config to running-config
Router#copy startup-config running-config

6: Change the password
Router#config t
Router(config)#enable secret cisco

7: Reset the configuration register to the default value
Router(config)#config-register 0x2102

8: Reload the router


Backing up the Cisco IOS

Restoring or Upgrading the Cisco IOS

Backing up the Configuration


Restoring the Configuration