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Cisco IOS in a Nutshell, 2nd Edition by James Boney

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Name

config-register — global

Synopsis

config-register value

Configures

Sets the configuration register

Default

Depends on the product

Description

This command allows the user to change the configuration register. Setting the configuration register is useful for recovering lost passwords and remedying other situations.

value

The value to set in the configuration register. The register is 16 bits wide, so legal values range from 0x0 to 0xFFFF in hexadecimal (0 to 65,535 decimal). Table 17-5 shows the significance of the bits in the configuration register. (There are some differences in bit assignments on different products; check your documentation.)

Table 17-5. Configuration register settings

Bit number

Value

Action

00

0x0000

Remains at the system bootstrap prompt.

01

0x0001

Boots system image on EPROM.

02,03

0x0002-0x000f

Specifies a Netboot filename, where the filename is in the form cisco n -processor_name. The n in the filename is taken from the hexadecimal value of these bits.

06

0x0040

Ignores NVRAM contents.

07

0x0080

Enables OEM bit.

08

0x0100

Breaks disabled. If you enable this bit, the break key can cause the router to go to boot ROM at any time. During the first 60 seconds of bootup, the break key is enabled no matter what this bit field is set to.

10

0x0400

Sets the IP broadcast address to all zeros.

05,11,12

0x0020,0x0800, 0x1000

Sets the console line speed. See next table for more information.

13

0x2000

Boots ...

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