Password Recovery for Cisco routers

Cisco router is one of the widely used computer network communication devices. In daily operation, the router plays an important role in the whole system, and it is unavoidable to operate it frequently. For example:

Modify router configuration files, diagnose network failures, and so on. Once the password is forgotten, it can cause great trouble to the job, at this point, how to recover the password becomes particularly important.

Flash Memory is read-only, so to modify the Flash Memory, the content, first to enter the boot ROM monitor operating mode.

. ROM Monitor operating environment is mainly used for password recovery.

To enter a different operating environment, you need to set the configuration register value, as described in the following table register value and the relationship between the operating environment to meet the needs of different operating environments.

Operating Environment and register Value

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Run Environment prompt Registervalue main application

IOS router> 0x2102 normal operation mode

Boot ROM Monitor Router (boot) > 0x1 operating system version upgrade

ROM Monitor > 0x0 Password recovery

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Configuration Register value and its meaning:

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Configurationregistervalue meaning

0x2102 default settings.

bit13=0x2000 Flash boot fails 5 times and automatically boots from ROM.

BIT8=0X0100 closes the break key.

Boot field=0x2 boot normal operating mode from Flash.

0x2101

bit13=0x2000 Flash boot fails 5 times and automatically boots from ROM.

BIT8=0X0100 closes the break key.

Boot field=0x1 into boot ROM operating mode. Router (boot) >

0x142

bit8=0x0040 into Rom monitor run mode. >

Boot field=0x2 boot normal operating mode from Flash.

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When a user forgets or incorrectly modifies a password and needs to be recovered, follow these steps:

1. Enter ROM Interrupt state

2. read out the current boot mode:

>e/s2000002

3. Make the following changes, ignoring the NVRAM guide:

>o/r0x**4*

4. The heavy phenol is good?: >i

5. Enter Steup mode, answer No to all questions

6. Access to super users:

Router>enable

7. NVRAM Download:

Router#config Memory

8. Restore the initial boot value and activate all ports:

"Hostname" #config terminal

"hostname" (config) #config-register 0x "value"

"Hostname" (#config) #interface xx

"Hostname" (config-if) #no shutdown

9. Query Password:

"Hostname" #show configuration (show Startup-config)

10. Modify and Store password:

"Hostname" #config terminal

"Hostname" (config-line) #line CONSOLE0

"Hostname" (config-line) #login

"Hostname" (config-line) #password xxxxxxxx

"Hostname" (config-line) # (CNTL-Z)

"Hostname" #write memory (copy running-config startup-config)

11. Restore Registervalue to its default settings:

Otherwise, the configuration that has been made after the router is reset may be lost!

"Hostname" #config terminal

"hostname" (config) #config-register 0x2102