Upgrading IOS on cisco routers

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splashA while ago a did a tutorial on upgrading the IOS on cisco switches. Now I am going to teach you how to upgrade your IOS on a cisco router. I have done this today with an 1841 and a 2610. Firstly I am going to assume you are here because you want to do this on your own lab equipment and you know a thing or two about cisco and IP addressing ,etc.

  1. Obtain a IOS image for your chosen router (http://certs4u.info/ciscoios/) the most important thing here is to make sure you chose the right image file for your router and make sure your flash is big enough to fit it! You can check your router model and flash size by doing a show version
    Router# show version

    This will also tell you your model number.show_version

  2. Next you want to get a TFTP server up and running, I recommend Solarwinds (download at end of article) Fill out the form and download the software. It’s pretty straight forward set your TFTP root to where you IOS is.  In the server bindings tab you want to set it to your nic where you setup a static IP (I used
  3. Now that you have your computer setup with an IP and a TFTP server, jump over to your router and setup a simple interface with an ip.
    ESW1(config)#int fa0/0
    ESW1(config-if)#ip address
    ESW1(config-if)#no shut

    Of course you interface and router name will vary. Test it out and ping your PC. It should work if not then troubleshoot! The main problem usually is windows firewall which you can just turn off for now. Also remember that a router to a PC is a cross-over cable; However most NIC’s now days are auto-sensing so it probably doesn’t matter.

  4. With a successful connection from your router to your PC you can now backup your current IOS image (This step isn’t essential but it is good practice just in case the new image messes up) type dir to bring up a list of files in your flash memory. You should see you IOS image, it will end in a .bin
    Router# dir

    Now copy the file to your TFTP server:

    Router# copy flash tftp

    run through the prompts answering the simple questions: filename, remote IP, etc.
    You will see the router transferring the file and it will display !!!!!! as it copies, you will also see the logs on the TFTP console. If you get an error then try again or the router will tell you what went wrong ie. wrong filename.

  5. Now to clear the flash memory to make room for your new image.
    Router# delete flash

    It will ask you to confirm each file.

  6. Do the reverse of what we did in step 4.
    Router# copy tftp flash

    tftp_serverrun through the prompts again, remembering that the filename you want is the filename of the newly acquired IOS image in the root directory of your TFTP root. Again you will see the !!!!!! as the file is copied.

  7. Tell the router to boot from the new image file, you must be in configure-terminal to do this!
    Router# conf t
    Router(config) boot system flash:<FILENAME OF NEWLY DOWNLOADED FILE>

    don’t include the < > of course.

  8. Reload the router
    Router(config) do reload

    don’t save the config changes! so press N.

  9. The router will then reload and hopefully start with the new image loading! If something went bad you will probably be loaded into ROMMON. I have done this twice today on two different routers with no problems. Just remember you must have enough room on your flash memory for the new image!

I hope all went well for your upgrade, if you have any issue feel free to comment below or tweet me @ompster

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