What Command Is Used To View The Current Router Configuration Register?

What is Configuration Register?

Configuration Register is a special 16 bits value that can be configured in Cisco routers. It is mainly used in three cases;

To determine how the router boots
To determine boot options
To set up panel speed

During the boot, router checks its software and the configuration files. To determine these files, router firstly check Configuration Annals. Co-ordinate to its value, router determines what to practice.

Configuration Register Configuration is particularly used for Router Password Recovery. So, what are the values of this special number?

config-register

Configuration Register 0x2102

The default value of Config Annals is 0x2102. With Configuration Annals 0x2102 value, the router boots from NVRAM and the normal router precedures works. The configuration stored in NVRAM is the startup configuration. And so, if we need to bypass this configuration, we can change the default value. Especially during Router Password Recovery, this simple configuration is washed.

We can check this value on Cisco routers with "show version" command. At the output of "show version" control, Configuration Annals value volition be at the bottom.

Router# testify version

Cisco IOS Software, C800 Software (C800-UNIVERSALK9-M), Version 15.two(4)M4, RELEASE SOFTWARE (fc2)

Technical Support: http://world wide web.cisco.com/techsupport

Compiled Thu 20-Jun-xiii 16:fourteen by mnguyen

ROM: Arrangement Bootstrap, Version 15.2(2r)T, RELEASE SOFTWARE (fc1)

Router uptime is 35 minutes, xiv seconds

Arrangement returned to ROM by power-on

System image file is "flash:c800-universalk9-mz.SPA.152-four.M4.bin"

…

Configuration annals is 0x2102

config-register-2102-vs2142

Config Annals 0x2142

To bypass NVRAM configuration, in other words, to bypass start-up configurataion, we tin can change Config Register value. Here, the new value that we will ready will be Configuration Annals 0x2142.

How to Modify Configuration Annals?

At that place are two way to alter Config Register on a router. This can be washed both in Rommon mode and in configuration mode.

In Rommon mode, it tin can be alter with "confreg" command. Beneath, we are changing Configuration Annals equally 0x2142.

rommon > confreg 0x2142

Later this configurationi we should reset the router to utilise this new value,or to forcefulness the router kick through this config register.

The other mode is configuring on configuration mode with "config- register" control.

Router# configure final

Router(config)# config-register 0x2142

Subsequently configuration, you can check the ne value and exist sure near the value.

Router# show version

Cisco IOS Software, C800 Software (C800-UNIVERSALK9-M), Version 15.2(4)M4, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Compiled Thu twenty-Jun-13 16:14 by mnguyen

ROM: Organisation Bootstrap, Version 15.2(2r)T, RELEASE SOFTWARE (fc1)

Router uptime is 35 minutes, 14 seconds

Arrangement returned to ROM by power-on

System image file is "flash:c800-universalk9-mz.SPA.152-4.M4.bin"

Configuration register is 0x2102 (will be 0x2142 at adjacent reload)

Again, we should reload the router for the new config annals to have result.

Router# reload

Organisation configuration has been modified. Save? [yeah/no]: n

Proceed with reload? [confirm]

You lot can find the detailed information about Config Register on Cisco Page.