Chapter 4 Troubleshooting the Installation
Performing Other Configuration Tasks
4-8
Cisco 12404 Internet Router Installation and Configuration Guide
OL-11636-01
Bits in the Software Configuration Register
This section provides more detailed descriptions of the significance of the bits in
the software configuration register and how they interact during the boot process.
As described earlier in
, the boot field setting
determines the source of the Cisco IOS software image that is used to boot the
router. If you set the boot field value to 0 (0x0000), you must boot the operating
system manually by entering the
boot
command at the ROM monitor prompt
(
rommon>
) on the system console.
If you set the boot field value to
0x2 through 0xF
and a valid
boot
system
command is stored in the configuration file, the router boots the Cisco IOS
software image as directed by that value. If no
boot system
command is present
in the configuration file, the router forms a default boot filename and attempts to
acquire that file from a network TFTP server.
In the following example, the software configuration register is set to boot the
router from the Flash memory SIMM on the RP and to ignore the Break function
at the next reboot of the system:
Filo#
configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Filo(config)#
config-register 0x0102
Filo(config)#
boot system flash
filename
Ctrl-Z
Filo#
With the configuration register set to 0x0102, the system computes a default boot
filename. In forming this filename, the system starts with
cisco
and appends the
octal equivalent of the boot field number, a hyphen, and the processor type (
grp
or
prp
).
lists the range of possible computed default filenames for booting over
the network. A valid
boot system
configuration command stored in the NVRAM
configuration file overrides any computed default filename for booting over the
network.
todd.book Page 8 Tuesday, November 27, 2007 6:02 PM
