Cisco Systems Cisco 12008 manual Definition of Bits in the Software Configuration Register

Performing Other Configuration Tasks

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Force an automatic boot using a boot image.

When you first power on the router, a boot image called the RP ROM monitor is executed, resulting in the display of the ROM monitor prompt (rommon>). At this prompt, you have access to a limited set of commands that enable you to set values in the software configuration register and to perform a number of other tasks.

The RP ROM monitor is loaded into the RP Flash ROM during board manufacture. You can use it to boot the system from local Flash memory devices; the RP ROM monitor software can be upgraded in the field, if necessary.

Read boot system commands from the configuration file stored in NVRAM.

Table 4-3 defines the bits in the software configuration register. The factory default value for the software configuration register is 0x0102. This value is a combination of the following: binary bit 8 = 0x0100 and binary bits 00 through 03 = 0x0002 (see Table 4-3).

Caution To avoid confusion, note that valid software configuration register values may be combinations of settings, rather than the individual settings listed in Table 4-3. For example, the factory default value 0x0102 for the software configuration register is actually a composite of settings in this register.

Table 4-3	Definition of Bits in the Software Configuration Register
Bit Number	Hexadecimal Value	Meaning/Function
00 through 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 4-4).
06	0x0040	Causes system software to ignore the contents of
		NVRAM.
07	0x0080	The OEM1 bit is enabled.
08	0x0100	The Break function is disabled.
09	0x0200	Use a secondary bootstrap.
10	0x0400	Internet Protocol (IP) broadcast with all zeros.

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