Installation guide

Cisco 4000 Series Virtual Configuration Register D-5
Virtual Configuration Register Settings
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 D-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 booting from a network
(TFTP) server.
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 attempt to boot from a network (TFTP) server 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:
router# configure terminal
Enter configuration commands, one per line.
Edit with DELETE, CTRL/W, and CTRL/U; end with CTRL/Z
config-register 0x102
Ctrl-Z
router#
The server creates a default boot filename as part of the automatic configuration processes.
To form the boot filename, the server starts with cisco and links the octal equivalent of the
boot field number, a dash, and the processor-type name. Table D-3 lists the default boot
filenames or actions for the processor.
Note A boot system configuration command in the router configuration in NVRAM
overrides the default netboot filename.