ROUTER COMPONENT(including )

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

BOOTING SEQUENCE:

 • Router performs a POST

• Bootstrap looks for & loads the Cisco IOS

• IOS software looks for a valid configuration file

• Startup-config file (from NVRAM) is loaded

                      – If startup-config file is not found, the router will start the setup mode

Configuration Registers

• Register

– 16-bit software written into NVRAM

– Loads from flash memory & looks for the startup-config file

• Configuration Register Bits

– 16 bits read 15-0, from left to right

– default setting: 0x2102

Register 2 1 0 2___

Bit number 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Binary 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0

NOTE: 0x means the digits that follow are in hexadecimal

BOOT FIELD MEAN

Checking the Register Value

Router#sh version

Cisco Internetwork Operating System Software

IOS ™ C2600 Software (C2600-I-M), Version 12.0(3)T3

RELEASE SOFTWARE (fc1)

[output cut]

Configuration register is 0x2102

Changing the Configuration Register

• Force the system into the ROM monitor mode

• Select a boot source & default boot filename

• Enable or disable the Brreak function

• Set the console terminal baud rate

• Load operating software from ROM

• Enable booting from a TFTP server

Router(config)#config-register 0x0101

Router(config)#^Z

Router#sh ver

Configuration register is 0x2102 (will be 0x0101 at next reload)

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

STEP BY STEP PROCEDURE:

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

Change the password

Router#config t

Router(config)#enable secret ciisco

7. Reset the configuration register to the default value

Router(config)#config-register 0x2102

8. Reload the router