User guide

B-20 Cisco 2500 Series Access Server User Guide
Virtual Configuration Register Settings
Step 6 Reboot the access server. The new value takes effect. Configuration register
changes take effect only when the server restarts, which occurs when you switch
the power off and on or when you issue a reload command from the console.
Virtual Configuration Register Bit Meanings
The lowest four bits of the virtual configuration register (bits 3, 2, 1, and 0) form the boot
field. (See Table B-3.) 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, as follows:
> b [tftp] flash filename
The b command options are as follows:
• b—Boots the default system software from ROM
• b flash—Boots the first file in Flash memory
• b filename [host]—boots from the network using a TFTP server
• b flash [filename]—Boots the file filename from Flash memory
For more information about the command b [tftp] flash filename, refer to the publication
Router Products Configuration Guide.
If you set the boot field value to a value of 0x2 through 0xF, and there is a valid system boot
command stored in the configuration file, then the access server boots the system software
as directed by that value. If you set the boot field to any other bit pattern, the access server
uses the resulting number to form a default boot filename for booting from the network
using a TFTP server. (See Table B-4.)
Table B-4 Default Boot Filenames
Action or Filename Bit 3 Bit 2 Bit 1 Bit 0
bootstrap mode 0 0 0 0
ROM software 0 0 0 1
cisco2-igs 0 0 1 0
cisco3-igs 0 0 1 1