Here’s some basics about upgrading a device’s IOS version using TFTP. The idea is to copy a new version into the device’s flash storage using the aforementioned protocols, reboot the device into the new IOS image, then delete the old image.

Verify the Current Version

  • View the current IOS version with show version
    • Take note of the version and name of the currently installed IOS

Transferring the New Image

  • copy tftp: flash:
    • Tell the router to copy from tftp: to flash:
  • When prompted for the ‘Address or name of remote host’ enter the TFTP server’s IP address.
  • When prompted for the ‘Source filename’ enter the entire file name of the new IOS image (it will probably be really long an annoying, and you’ll need access to the TFTP server to view the file before you transfer it)
  • When prompted for ‘Destination filename’ enter the name you want to save the file as
  • After a short time (or maybe a long time, depending on the network and the image size) the transfer should be complete.

Booting the New Image

  • (config)#boot system flash:filename
    • Tell the device which image to use for the next system boot.
  • write memory
    • You need to save the configuration, or the system won’t actually change the boot device
  • reload
    • Reboot the device

Verify the New Version

  • show version
    • You should now see the updated IOS version

Delete the Old Version

  • delete flash:filename
    • Deletes the old IOS image from memory. You may or may not want to do this immediately after upgrading. In theory the old image is just taking up space, but in the event of a security vulnerability or bug being discovered in the new version, it may be good to hang on to the old version so you can easily switch back. Your company likely has best practices on this already documented.