How Do I Verify The Configuration Register On A Cisco 2500 Router?

What is Configuration Register?

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

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

During the boot, router checks its software and the configuration files. To determine these files, router firstly cheque Configuration Annals. According to its value, router determines what to practise.

Configuration Register Configuration is peculiarly used for Router Password Recovery. And so, what are the values of this special number?

config-register

Configuration Register 0x2102

The default value of Config Register is 0x2102. With Configuration Register 0x2102 value, the router boots from NVRAM and the normal router precedures works. The configuration stored in NVRAM is the startup configuration. So, if we demand to bypass this configuration, nosotros tin change the default value. Especially during Router Countersign Recovery, this simple configuration is done.

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

Router# bear witness version

Cisco IOS Software, C800 Software (C800-UNIVERSALK9-One thousand), Version 15.ii(4)M4, RELEASE SOFTWARE (fc2)

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

Compiled Thu 20-Jun-13 16:fourteen past mnguyen

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

Router uptime is 35 minutes, 14 seconds

System returned to ROM past ability-on

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

…

Configuration register is 0x2102

config-register-2102-vs2142

Config Register 0x2142

To bypass NVRAM configuration, in other words, to bypass start-upward configurataion, we can alter Config Register value. Here, the new value that we will set will exist Configuration Register 0x2142.

How to Alter Configuration Annals?

In that location are two way to change Config Register on a router. This can be washed both in Rommon manner and in configuration mode.

In Rommon way, information technology can be change with "confreg" control. Below, we are irresolute Configuration Register as 0x2142.

rommon > confreg 0x2142

After this configurationi we should reset the router to employ this new value,or to force the router kick through this config register.

The other fashion is configuring on configuration style with "config- register" command.

Router# configure last

Router(config)# config-annals 0x2142

Subsequently configuration, you tin can check the ne value and be sure almost the value.

Router# show version

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

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

Compiled Thu xx-Jun-xiii sixteen:14 by mnguyen

ROM: System Bootstrap, Version 15.ii(2r)T, RELEASE SOFTWARE (fc1)

Router uptime is 35 minutes, fourteen seconds

System returned to ROM by power-on

Organization 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 register to take result.

Router# reload

Arrangement configuration has been modified. Save? [yes/no]: n

Go on with reload? [confirm]

You can detect the detailed information virtually Config Register on Cisco Page.