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Appendix A
Using the ROM Monitor
Table A-1
Bit
12–11
10
9
8
7
6
5–4
3–0
For example, for normal operations the configuration register is set to 0x2102, which sets bit 13 (allows
the router to fall into ROMMON mode if the boot fails), bit 8 (allows the user to break into ROMMON),
and bit 1 (boots a Cisco IOS software image). Bits 11 and 12 are cleared, which sets the console port to
9600 bps.
The following are the most commonly-used configuration register values:
•
•
•
•
Tip
The confreg command is identical in function to the config-register command that is available in global
configuration mode.
Examples
The following example shows how to change the configuration register by using the English prompts. In
this example, the only change is to have the router boot the Cisco IOS software image instead of entering
ROMMON mode:
rommon 1 > confreg
OL-1581-07
Configuration Register Bit Field Descriptions (continued)
Description
Defines the speed, in bps, for the console port:
00 = 0x0000 = 9600
01 = 0x0800 = 4800
10 = 0x1000 = 1200
11 = 0x1800 = 2400
On the Cisco CMTS routers, the console port speed is fixed at 9600 bps and
Note
cannot be changed.
If set, uses an IP broadcast address that consists of all ones (for example, 0x0400).
If set, disables the secondary bootstrap (for example, 0x0200).
If set, the router enables the BREAK key, allowing users to break into ROMMON
during the boot process (for example, 0x0100).
Unused on the Cisco CMTS routers.
If set, the router ignores the configuration file in its Flash memory. This is typically
done when the user has forgotten the router's enable password (for example, 0x0040).
Unused on the Cisco CMTS routers.
Defines the router's boot behavior:
0x0000 = Boots to the ROMMON prompt
0x0001 = Boots the ROMMON boot helper software (first file in bootflash:)
0x0002 to 0x000F = Boots a Cisco IOS software image, based on the values of the
router's boot variables. Each boot system command in the configuration file is tried
until a valid image is booted.
0x0 = Boot into ROMMON.
0x2002 = Normal boot for standard operations, but the BREAK signal cannot be used to break into
ROM monitor mode.
0x2102 = Normal boot for standard operations, enabling the BREAK signal.
0x2142 = Normal boot but the router ignores the configuration file in Flash memory.
Cisco Broadband Cable Command Reference Guide
confreg
A-15
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