Changing Configuration Register Settings - Cisco EF4116 Hardware Installation And Maintenance Manual

Virtual Configuration Register Settings

Changing Configuration Register Settings

Some common reasons to modify the value of the virtual configuration register follow:
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a filename from which to boot a default system image stored on a network server. (See Table B-3.)
To change the configuration register while running the IOS software, follow these steps:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
B-2 Cisco 4000 Series Hardware Installation and Maintenance
Recover a lost password.
Change the console baud rate.
Enable or disable the Break function.
Manually boot the operating system using the b command at the ROM monitor prompt.
Force the router to boot automatically its system image in Flash memory, or boot as per any
boot system commands that are stored in its configuration file in NVRAM.
If the router finds no boot system commands, it uses the configuration register value to form
Enter the enable command and your password to enter the privileged level, as follows:
router> enable
Password:
router#
At the privileged-level system prompt (router #), enter the command
You will be prompted as shown in the following example:
router# configure term
Enter configuration commands, one per line.
Edit with DELETE, CTRL/W, and CTRL/U; end with CTRL/Z
To set the contents of the configuration register, enter the config-register value
configuration command where value is a hexadecimal number preceded by 0x
(see Table B-3), as in the following:
config-register 0xvalue
(The virtual configuration register is stored in nonvolatile memory.)
Exit the configuration mode by entering Ctrl-Z. The new value settings will be saved to
memory; however, the new settings do not take effect until the system software is reloaded
by rebooting the router.
To display the configuration register value currently in effect and the value that will be used
at the next reload, enter the show version EXEC command, and the value will be displayed
on the last line of the screen display as in the following example:
Configuration register is 0x142 (will be 0x102 at next reload)
Reboot the router. The new value takes effect. Configuration register changes take effect
only when the server restarts, for example, when you switch the power off and on or when
you issue a reload command from the console.
configure terminal.