Bridge/Router Installation and Configuration Guide

Chapter 4 System Startup and Basic Configuration
Configuring the Software Configuration Register
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Cisco 12016, Cisco 12416, and Cisco 12816 Router Installation and Configuration Guide
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• Read boot system commands from the configuration file stored in NVRAM.
Table 4-4 defines software configuration register bits.
Caution To avoid confusion and possibly halting the system, remember that valid software
configuration register values may be combinations of settings, rather than the
individual settings listed in
Table 4-4. For example, the default value for the
software configuration register (0x0102) is a combination of several settings
(binary bit 8 = 0x0100 and binary bits 00 through 03 = 0x0002).
Ta b l e 4-4 Software Configuration Register Bits
Bit Number Hexadecimal Value Meaning/Function
00 to 03 0x0000 to 0x000F Comprises the boot field for defining
the source of a default Cisco IOS
software image required to run the
router (see
Table 4-5)
06 0x0040 Causes the system software to ignore
the contents of NVRAM
07 0x0080 Enables the OEM
1
bit
1. OEM = original equipment manufacturer.
08 0x0100 Disables the break function
09 0x0200 Uses a secondary bootstrap
10 0x0400 Broadcasts Internet protocol (IP) with
all zeros
11 and 12 0x0800 to 0x1000 Defines the console baud rate (default
= 9600
bps)
13 0x2000 Boots the default flash memory
software if the network
boot fails
14 0x4000 Excludes network numbers from
IP
broadcasts
15 0x8000 Enables diagnostic messages and
ignores the contents of NVRAM