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Configuring the Boot Field
The lowest four bits of the processor configuration register (bits 3, 2, 1, and 0) form the boot field.
(See Table B-2.)
Table B-2
Boot Field Meaning
00
01
02-F
1. Values of the boot field are 2–15 in the form cisco<n>-processor_name, where 2 < n < 15.
The boot field specifies a number in binary. If you set the boot field value to 0, you must have console
port access to boot the operating system manually. Boot the operating system by entering the
b command at the bootstrap prompt as follows:
Definitions of the various command options follow:
For more information about the b [tftp] flash filename command, see the appropriate software
publications.
If you set the boot field value to a value of 2 through F, and there is a valid system boot command
stored in the configuration file, the router boots the system software as directed by that value.
(See Table B-3.) If you set the boot field to any other bit pattern, the router uses the resulting number
to form a default boot filename for netbooting.
If there are no boot commands in the configuration file, the router attempts to boot the first file in
system Flash memory. If no file is found in system Flash memory, the router attempts to netboot a
default file whose name is derived from the value of the boot field (for example: cisco2-4500). If the
netboot attempt fails, the boot helper image in boot Flash will boot up.
If boot commands are in the configuration file, the router software processes each boot command in
sequence until the process is successful or the end of the list is reached. If the end of the list is
reached without a file being successfully booted, the router will retry the netboot commands up to
six times unless the boot default ROM software if netboot fails bit (bit 13 of the virtual configuration
register) is set. If bit 13 is set, the system boots the boot helper image found in boot Flash memory
without any retries.
In the following example, the virtual configuration register is set to boot the router automatically
from Flash memory and to ignore Break at the next reboot of the router:
Explanation of Boot Field (Configuration Register Bits 00–03)
Stays at the system bootstrap prompt (ROM monitor) on a reload or
power cycle
Boots the boot helper image as a system image
Specifies a default netboot filename
Enables default booting from system Flash memory
Enables boot system commands that override default netboot filename
> b [tftp] flash filename
b—Boots the default system software from ROM
b flash—Boots the first file in Flash memory
b filename [host]—Boots over the network using TFTP
b flash [filename]—Boots the file (filename) from Flash memory
Virtual Configuration Register Settings
1
Cisco 4000 Series Virtual Configuration Register B-3
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Troubleshooting
