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Router boots into boot mode without any  errors displayed on  the console

Core Issue

A router may be stuck in boot mode because the configuration register is set incorrectly. This is the prompt reached by the router:

router(boot)>

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

Resolution

To resolve this issue, perform these steps:

  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.

  • 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.
  • 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]
Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 04:04 PM
Updated by: