Installation Manual

4-9
Troubleshooting
Virtual Configuration Register Settings
Maintenance
Changing Configuration Register Settings
Take the following steps to change the configuration register while running
the Cisco IOS software:
1. Enter the enable command and your password to enter privileged mode:
Router> enable
Password:
Router#
2. Enter the
configure terminal
command at the privileged EXEC prompt
(Router#):
Router# configure terminal
3. To set the contents of the configuration register, enter the configuration
command config-register value, where value is a hexadecimal number
preceded by 0x (see table 4-3 and table 4-4):
config-register 0xvalue
(The virtual configuration register is stored in NVRAM.)
Table 4-4. Explanation of Boot Field (Configuration Register Bits 00 to 03)
4. Press Ctrl-Z to exit configuration mode. The new settings will be saved
to memory; however, the new settings do not take effect until the system
software is reloaded by rebooting the router.
5. 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. The value displays on the last line of the screen display:
Configuration register is 0x142 (will be 0x102 at next reload)
Boot Field Boot Process
0x0 Stops the boot process in the ROM monitor
0x1 Stops the boot process in the boot ROM monitor
0x3–0xF Specifies a default filename for booting over the network from a TFTP
server
Enables boot system commands that override the default filename for
booting over the network from a TFTP server
0x2 Full boot process, which loads the Cisco IOS image from Flash memory
J3138.bk Page 9 Wednesday, March 18, 1998 6:07 PM