Prerequisites

1. IOS Image: Download the desired IOS image file from Cisco’s website.
2. TFTP Server: Set up a TFTP server on your computer.
3. Console Connection: Connect to the router using a console cable.
4. Backup: Back up the current configuration.

Step-by-Step Upgrade Process

1. Connect to the Router:

   • Open a terminal emulator (like PuTTY or Tera Term) and connect to the router via the console port.

2. Check Current IOS Version:

   • Use the following command to check the current IOS version:

Commnd——

show version

Backup Current Configuration:

• • It’s good practice to back up your current configuration:
  Commnd—–

  copy running-config startup-config
  copy startup-config tftp

   

  Copy the New IOS Image to the Router:

  • Use the TFTP server to transfer the new IOS image. First, configure the router’s interface with an IP address:

  Commnd—

  conf t
  interface <interface_name>
  ip address <ip_address> <subnet_mask>
  no shutdown
  exit

  • Then copy the IOS image:
   copy tftp: flash:

• • Follow the prompts to enter the TFTP server IP and the filename of the IOS image.

• Verify the New IOS Image:

  • dir flash:

• Set the Boot Variable:

  • Set the router to boot from the new IOS image:
    • conf t
      boot system flash flash:<your_ios_image.bin>
      exit

  • Save the Configuration:

    • Save the updated configuration Commnd : write memory

  • Reboot the Router:

    • Reload the router to apply the new IOS: reload

• Post-Upgrade Checks

  • show version

Troubleshooting Tips

• If the router fails to boot, access ROMMON mode and check your settings.
• Make sure the TFTP server is reachable and the IOS image is compatible with your router model.
• If needed, you can use conf t and boot system commands to revert to the previous IOS image if the new one doesn’t work.