Command Reference

config-register

To change the configuration register settings, use the config-register global configuration command.

config-register value

Syntax Description

value

Hexadecimal or decimal value that represents the 16-bit configuration register value that you want to use the next time the router is restarted. The value range is from 0x0 to 0xFFFF (0 to 65535 in decimal).

Default

Refer to your platform documentation for the default configuration register value.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

This command applies only platforms which use a software configuration register.

The lowest four bits of the configuration register (bits 3, 2, 1, and 0) form the boot field. The boot field determines if the router boots manually, from ROM, or from Flash or the network. To change the boot field value and leave all other bits set to their default values, follow these guidelines:

If you set the configuration register boot field to 0x0, you must boot the operating system manually with the boot command.
If you set the configuration register boot field to 0x1, the router boots using the default ROM software.
If you set the configuration register boot field to any value from 0x2 to 0xF, the router uses the boot field value to form a default boot filename for booting from a network server.

For more information about the configuration register bit settings and default filenames, see the appropriate router hardware installation guide.

Example

In the following example, the configuration register is set to boot the system image from Flash memory:

Router(config)# config-register 0x210F