Configuring The Software Configuration Register - Cisco 7500 Series Configuration Manual

Configuring the Software Configuration Register

Configuring the Software Configuration Register

Note Appendix A, "Configuration Register Information"
Cisco 7500 series routers use a 16-bit software configuration register, which allows you to set specific
system parameters. Settings for the software configuration register are written into NVRAM.
Following are some reasons for changing the software configuration register settings:
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Table 4-1
the boot field.
To avoid confusion and possibly halting the router, remember that valid configuration register settings
Caution
might be combinations of settings and not just the individual settings listed in
the factory default value of 0x0101 is a combination of settings.
Table 4-1
Bit Number
00 to 03
06
07
08
09
10
11 to 12
13
14
15
1. The factory default value for the configuration register is 0x0101.
Cisco 7500 Series Installation and Configuration Guide
4-4
To select a boot source and default boot filename
To enable or disable the Break function
To control broadcast addresses
To set the console terminal baud rate
To load operating software from Flash memory
To enable booting from a Trivial File Transfer Protocol (TFTP) server
To recover a lost password
To allow you to manually boot the system using the boot command at the bootstrap program prompt
To force the router to boot automatically from the system bootstrap software (boot image) or from
its default system image in onboard Flash memory, and read any boot system commands that are
stored in the configuration file in NVRAM
lists the meaning of each of the software configuration memory bits, and
Software Configuration Register Bit Meanings
1
Hexadecimal
0x0000 to 0x000F
0x0040
0x0080
0x0100
0x0200
0x0400
0x0800 to 0x1000
0x2000
0x4000
0x8000
This value is a combination of the following: bit 8 = 0x0100 and bits 00 through 03 = 0x0001.
Chapter 4 Performing a Basic Configuration of the System
also provides configuration register information.
Meaning
Boot field
Causes system software to ignore NVRAM contents
2
OEM bit enabled
Break function disabled
Use secondary bootstrap
Internet Protocol (IP) broadcast with all zeros
Console line speed (default is 9600 baud)
Boot default Flash software if network boot fails
IP broadcasts do not have network numbers
Enable diagnostic messages and ignore NVRAM contents
Table 4-2 defines
Table 4-1. For example,
OL-5008-03 B0