Tag Archive for 2500

Recovering IOS on a 2500 Series

Lab Prerequisites:

  • You’ll need a Cisco 2500 Series router that has a corrupt image or NO IOS image at all. If you wish to simulate this lab you can erase the flash on your device and reboot. Please note that you’ll need to backup the Cisco IOS image prior to erasing it unless you have another image on hand that you wish to load onto the device.
  • A console connection to the device is REQUIRED.
  • You’ll need a TFTP server installed on your PC to restore the image.

Lab Objectives:

  • Boot the Cisco router into ROM mode by breaking the boot sequence using the keystroke CTRL+Pause Break
  • Change the configuration register to boot the ROM(BOOT) image. Configuration register to be used is 0x2141
  • Initialize the router by issuing the  i  command
  • Assign an IP address to the ethernet interface and configure a default gateway (if required)
  • Copy the Cisco IOS image from the TFTP server into flash memory.
  • Change the configuration register back to its default value and reload the device to ensure that the device boots up properly with the restored IOS image.

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Cisco 2500 Series Password Reset

Lab Prerequisites:

  • A Cisco 2500 Series router that has an unknown console or enable password.
  • An active Serial Console session to the device that you’re unable to login to.

 

Lab Objectives:

  • Break the boot sequence when powering on the Cisco 2500 Series router to place yourself in rom monitor mode.
  • Change the configuration register to 0x2142 to make the router bypass the contents of NVRAM when booting then initialize the router (boot the router into IOS).
  • (Option 1) – Once booted, place yourself into privileged mode and copy the start up-config to the running config. Afterward, you may change the line password or enable password and write the configuration by to NVRAM by issuing the copy run start command.
  • (Option 2) – Once booted, place yourself into privileged mode and do a write erase to clear the contents of the NVRAM.
  • Now change the configuration register back to 0x2102 to boot set the router to boot normally and load the NVRAM contents upon boot.

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