Want to learn more about router and switch management? Automatically sign up for our free Cisco Routers and Switches newsletter, delivered each Friday!
Have you ever accidentally wiped out the IOS on your router? If you're working quickly and not paying attention, it can be an easy mistake to make. All it takes is making a typo in the destination filename when you're trying to save a change.
Here's an example:
router# copy running-config startp-config Destination filename [startp-config]? Erase flash: before copying? [confirm] Erasing the flash filesystem will remove all files!
Hitting [Enter] a couple of times out of habit can all too quickly wipe out the IOS. If you don't realize the mistake in time, rebooting the router means the IOS is gone for good, and the router won't boot up.
Losing the IOS can also happen when upgrading the flash on the router. As the Cisco IOS grows larger, having to upgrade your flash is a very common task. But when you install the new flash, it has no IOS, leaving you in the same position as if you had accidentally erased the flash.
Unfortunately, if you're like many people, when you wipe out the IOS, you may not have a backup copy of the IOS. Or, you may not have access to the Cisco IOS download site or have the time to download the somewhat large IOS file.
And if you're looking for the same IOS on all of your routers, it can be difficult to locate it on the Cisco IOS download site. Many times, it's much easier to take the IOS from an existing router and restore it on the router that's missing its IOS.
Let's look at the step-by-step process for restoring the Cisco IOS to a router using this method.
Install a TFTP server
First you need to install a (TFTP) server. I recommend the Tftpd32 server, which you can download from the Web. This is a great TFTP server, without a lot of the fluff that most of the others have. At less than 1 MB, it's very small and has no install application.
Run the TFTP server on a PC
If you've just pulled the working router off a shelf, you can connect the PC to the router with a reverse Ethernet cable. Configure the router and PC on the same network. Make sure that you can ping the router and that the router can ping you.
If your working router is up on your network, you can just download the IOS over the network directly using instructions in the next section.
Copy the IOS from the working router to the PC
Here's an example of how to accomplish this:
copy c2600-12-3.xxxx.bin tftp://10.253.15.72
Replace 10.253.15.72 with the IP address of your PC, and replace c2600 with the name of your IOS. (You can locate the name of the IOS on the working router using the show flash command.)
This saves the IOS on the PC in the directory configured by the TFTP server. Figure A shows an example of what it looks like while downloading. Make sure to note the directory in which you'll save the IOS.