Thought I would add this to my blog to help anyone that was in the same situation I had back in April. A big thanks to Richard Morrell ( @richardmorrell ) for this!
If you have a Cisco router which is unable to boot it’s IOS (flash image is corrupted, lost or wrong build), then you can boot the rommon and ask it to TFTP a replacement image across. It is preferable you have a working flash device in the router to save the flash image to, but you can just boot it straight from TFTP to memory if you’re desparate. Pre-requesits: Continue reading