There are two main methods to return a Cisco router to its original factory defaults. These two methods are described below.

 First Method

This method uses the config-register 0×2102 command in global configuration mode.

  • First check the configuration register on the router by issuing the show version command. The configuration register setting is displayed in the last line of the show version command output and should be set to 0×2102. If this is not the case, enter the config-register 0×2102 command once in global configuration mode.
    router#configure terminal
    router(config)#config-register 0x2102
    router(config)#end
    router#

    If the show version command is issued again, the same line in the command output will have ‘(will be 0×2102 at next reload)‘ appended to the current register setting.

  • Erase the current start-up configuration on the router with the write erase command.
  • Reload the router with the reload command. When prompted to save the configuration, DO NOT save.
    router#reload
    System configuration has been modified. Save? [yes/no]: n
    Proceed with reload? [confirm]

    Once the router reloads, the System Configuration Dialog appears.

             --- System Configuration Dialog ---
    Would you like to enter the initial configuration dialog? [yes/no]:

    The router is now reset to the original factory defaults.

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    Second Method

    This method uses the config-register 0×2142 command in global configuration mode.

  • Enter the config-register 0×2142 command in global configuration mode.
    router(config)#config-register 0x2142

    This causes the router to ignore the start-up configuration on the next reload. If a show version is issued, the last line in the command output will have ‘(will be 0×2142 at next reload)‘ appended to the current configuration register setting.

  • Reload the router using the reload command in enable mode. It is not necessary to save when prompted to save the system configuration.
    router#reload
    System configuration has been modified. Save? [yes/no]: n
    Proceed with reload? [confirm]

    After the router has reloaded, the System Configuration Dialog appears.

  • Enter no to the question “Would you like to enter initial configuration dialog?”
  • Change the configuration register setting to 0×2102 by entering the config-register 0×2102 command once in global configuration mode.
  • Issue the write memory command in enable mode to overwrite the existing start-up configuration with the current running configuration.
  • Reload the router with the reload command in enable mode.Once the router reloads, the System configuration Dialog appears.
             --- System Configuration Dialog ---
    Would you like to enter the initial configuration dialog? [yes/no]:

    The router is now reset to the original factory defaults.