Cisco Systems GRP-B manual Configuration Register Bit Meanings, Default Boot Filenames

Implementing Additional Configuration and Maintenance Tasks

Step 5 Display the configuration register value currently in effect, which will be used at the next reload by entering the show version EXEC command.

The value is displayed on the last line of the screen display, as in the following example:

Configuration register is 0x141 (will be 0x2102 at next reload)

Step 6 Save your settings.

Configuration register changes take effect only after the system reloads, such as when you issue a reload command from the console.

Step 7 Reboot the system. The new configuration register value takes effect with the next system boot.

Configuration Register Bit Meanings

The lowest four bits of the software configuration register (bits 3, 2, 1, and 0) form the boot field. (See Table 10.) The boot field specifies a number in binary form. If you set the boot field value to 0, you must boot the operating system manually by entering the b command at the bootstrap prompt (>).

If you set the boot field value to 0x2 through 0xF and there is a valid boot system command stored in the configuration file, theCisco 12000 Series Router boots the system software as directed by that value. If there is no boot system command, the Cisco 12000 Series Router forms a default boot filename for booting from a network server. (See Table 11 for the format of these default filenames.)

In the following example, the software configuration register is set to boot the system from onboard Flash memory and to ignore Break at the next reboot of the system:

Router# conf term

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# config-register 0x2102

Router(config)# boot system flash [filename]

Crtl-z

Router#

The server creates a default boot filename as part of the automatic configuration process. To form the boot filename, the server starts with the name cisco and adds the octal equivalent of the boot field number, a hyphen, and the processor-type name (GRP).

Table 11 lists the default boot filenames. A boot system configuration command in the configuration file in NVRAM overrides the default filename created for booting over the network.

Note If a bootable Cisco IOS software image exists in a Flash memory card or Flash disk installed in PCMCIA slot 0 or slot 1, the configuration register setting is overridden, and the bootable Cisco IOS software image will be booted instead of the default TFTP-bootable Cisco IOS software image (cisco2-GRP through cisco17-GRP).

	Table 11	Default Boot Filenames
	Action/File Name		Bit 3	Bit 2	Bit 1		Bit 0
	Bootstrap mode		0	0	0		0
	Default software		0	0	0		1
	cisco2-GRP		0	0	1		0
	cisco3-GRP		0	0	1		1
						Configuring the Software Configuration Register
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