Using The Configuration Register; Using The Configuration Register In Global Configuration Mode; Appendix A Using The Rom Monitor - Cisco SR2016T-NA Reference Manual

Entering the ROM Monitor
Tip
Router# show version
Cisco Internetwork Operating System Software
IOS (tm) 7200 Software (UBR7200-P-M), Version 12.2(15)BC1, RELEASE SOFTWARE
TAC Support: http://www.cisco.com/tac
Copyright (c) 1986-2003 by cisco Systems, Inc.
...
16384K bytes of Flash PCMCIA card at slot 0 (Sector size 128K).
20480K bytes of Flash PCMCIA card at slot 1 (Sector size 128K).
4096K bytes of Flash internal SIMM (Sector size 256K).
Configuration register is 0x2102
Router# ^] <-- in this example, a CTRL-] is used to enter telnet command mode
telnet> send brk
*** System received an abort due to Break Key ***
signal= 0x3, code= 0x0, context= 0x6208b290
PC = 0x606b5ab0, SP = 0x80007e00, RA = 0x606d2370
Cause Reg = 0xffffffff, Status Reg = 0x3400ff03
rommon 1 >
Caution When you enter ROM monitor mode, the Cisco IOS software no longer is executing, and all of the
router's normal functions end. Do not enter ROM monitor mode on a Cisco CMTS that is being used for
production purposes because this immediately halts all network and subscriber traffic through that
Cisco CMTS until you restart the Cisco IOS software.
To resume execution after interrupting the boot process or Cisco IOS software, use the
Tip
at the ROM monitor prompt. To boot another software image, use the
prompt.

Using the Configuration Register

When the router initially boots, it passes control to the ROM monitor software, which uses the value of
the configuration register to determine the next step in the bootup process. You can change the value of
the configuration register by using the
config-reg command in global configuration mode.

Using the Configuration Register in Global Configuration Mode

To set the configuration register when the router is running the Cisco IOS software, use the config-reg
command in global configuration mode. Then use the reload command to reboot the router.
For example, the following commands set the configuration register to 0x00 so that the router boots into
ROM monitor mode. The reload command then reboots the router.
Cisco Broadband Cable Command Reference Guide
A-2
In this example, a CTRL-] is used to enter Telnet command mode, where the send brk command
is used to send the BREAK signal. Other terminal programs might use different commands.
confreg command in ROM monitor mode or by using the
Appendix A Using the ROM Monitor
cont command
boot command at the ROM monitor
OL-1581-07