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The configuration register is a four-character hexadecimal value that can be changed to manipulate how the router behaves at bootup. The default value is 0x2102.

The fourth character in the configuration register is known as the boot field. Changing the value for this character will have the following effects:

• 0x2100 = Always boot to ROMMON. There are very few good reasons to do this, except possibly for training or a practical joke.
• 0x2101 = Always boot to RXBOOT. Again, there are not many reasons to force this.
• 0x2102 through 0x210F = Load the first valid IOS in flash; values of 2 through F for the fourth character specify other IOS image files in flash.

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Posted by nicholsonfenix

Shortly we define Configuration register is a 16-bit, user-configurable value used by routers, with which you can set specific system parametersThe configuration register can be set from configuration mode using the config-register command.

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Posted by HamidAliKhan

Routers use a 16-bit software configuration register, with which you can set specific system parameters. Settings for the software configuration register are written into nonvolatile random access memory (NVRAM).

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Posted by burhanalipk

Configuration register is a 16-bit, user-configurable value used by routers, with which you can set specific system parametersThe configuration register can be set from configuration mode using the config-register command.

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Posted by sagitraz