router(boot)>

If the configuration register has been misconfigured, no errors will be logged to the console during the boot sequence.

1. Check the configuration register value by issuing the show version command. The configuration register is found in the last line of the command output, as shown in this example:

   router(boot)>show version
   Cisco Internetwork Operating System Software 
   IOS (tm) 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1)
   Copyright (c) 1986-1996 by cisco Systems, Inc.
   Compiled Fri 27-Dec-96 17:33 by loreilly
   Image text-base: 0x01010000, data-base: 0x00001000
   
   ROM: System Bootstrap, Version 11.0(10c), SOFTWARE
   
   router uptime is 4 minutes
   System restarted by reload
   Running default software
   
   cisco 2500 (68030) processor (revision N) with 14336K/2048K bytes of memory.
   Processor board ID 24554515, with hardware revision 00000000
   X.25 software, Version 2.0, NET2, BFE and GOSIP compliant.
   1 Ethernet/IEEE 802.3 interface.
   2 Serial network interfaces.
   32K bytes of non-volatile configuration memory.
   16384K bytes of processor board System flash (Read/Write)
   Configuration register is 0x2001

2. Change the value back to the default value of 0x2102, as shown in this example:

router(boot)>enable
router(boot)#config term
router(boot)(config)#config-register 0x2102
router(boot)(config)#exit
router(boot)#

For more information on the configuration register, refer to Use of the Configuration Register on All Cisco Routers.

3. To verify the configuration register change, issue the show version command at the router(boot)# prompt, and review the output again. Look for the configuration register setting, which should show a new value upon the next reload.

router(boot)>show version 
Cisco Internetwork Operating System Software 
IOS (tm) 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1996 by cisco Systems, Inc.
Compiled Fri 27-Dec-96 17:33 by loreilly 
Image text-base: 0x01010000, data-base: 0x00001000 

ROM: System Bootstrap, Version 11.0(10c), SOFTWARE 

router uptime is 5 minutes 
System restarted by reload 
Running default software 

cisco 2500 (68030) processor (revision N) with 14336K/2048K bytes of memory. 
Processor board ID 24554515, with hardware revision 00000000 
X.25 software, Version 2.0, NET2, BFE and GOSIP compliant.
1 Ethernet/IEEE 802.3 interface.
2 Serial network interfaces.
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read/Write)
Configuration register is 0x2001
!-- This will be 0x2102 at the next reload.

4. Once the router is reloaded, the new configuration register setting becomes active. This is an example of how to reload your router:

   Note: Do not save the configuration while the router is in boot mode. Avoid using the save commands (write memory or (copy running-config startup-config), and answer no to any prompt suggesting that you save your current configuration. If you save the configuration while the router is in boot mode, the configuration may be partially or completely erased. The config-register command is the only Cisco IOS® Software configuration command which does not get saved in NVRAM. It changes the configuration register immediately, but this takes effect only during the next boot.

   router(boot)#reload
   System configuration has been modified. Save? [yes/no]: n
   Proceed with reload? [confirm]