4-5
Cisco 7500 Series Installation and Configuration Guide
OL-5008-03 B0
Chapter 4 Performing a Basic Configuration of the System
Configuring the Software Configuration Register
Configuration Register Bit Meanings
The lowest four bits of the software configuration register (bits 3, 2, 1, and 0) form the boot field. 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
Definitions of the various b command options follow:
•
b—Boots the default system software from Flash memory
•
b flash—Boots the first file in onboard Flash memory
•
b slot0: filename—Boots the file filename from the Flash memory card in PC Card slot 0
•
b slot1: filename—Boots the file filename from the Flash memory card in PC Card slot 1
•
b filename [host]—Boots from server host using TFTP
•
b flash: [filename]—Boots the file filename from onboard Flash memory (abbreviated form of the
boot system flash command shown below)
For more information about the b [tftp | flash ] [filename] command, refer to the set of configuration
fundamentals publications listed in the
“If You Need More Configuration Information” section on
page 4-32
.
If you set the boot field value to 0x2 through 0xF and there is a valid boot system command stored in
the configuration file, the router boots the system software as directed by that value. If there is no boot
system command, the router forms a default boot filename for booting from a network server. (See
Table 4-3
for the format of these default filenames.)
In the following example, the software configuration register is set to boot the router from onboard Flash
memory and to ignore the Break function at the next reboot of the router:
Router# conf term
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# config-register 0x102
Router(config)# boot system flash [filename]
Crtl-Z
Router#
Table 4-3
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
filename created for booting over the network.
2.
OEM = original equipment manufacturer.
Table 4-2
Explanation of Boot Field (Configuration Register Bits 00 to 03)
Boot Field
Meaning
00
Stays at the system bootstrap prompt
01
Boots the first system image in onboard Flash memory
02 to 0F
Specifies a default network boot filename
Enables boot system commands that override the default network boot filename