While going through some examples on my CCNA Security book I found the version of IOS that I had on my 2811 Router would not support Network Objects. So I went online Cisco.com to obtain a newer IOS for the router. My model only has a 64 MB Flash card, so I had to take that into consideration when looking for a replacement IOS. The other issue that I found was the previous IOS was hidden on the flash card, and showed only 31 MB free out of the 64 MB . I used the format feature on CCP, however that only formated the 31 free MB portion and left the remaining section untouched.
What I ended up doing was using the erase flash command at the CLI which then formated the flash as well as did a low level of the DOS partion it said it found on the flash drive. This was all done before I got my hands on the device by the way, so I am not really sure what the previous owner did with the flash and IOS image.
After the erase procedure I was able to TFTP to the router and upload my new 15.1 IOS version (I was on 12.4). Then it was just a matter of using the boot system flash:/ command to point to my new IOS image, save my config, and reload the router. In all the procedure went well and now I am able to follow along with the various examples in the text.
Lately I have been getting a lot of practice at upgrading IOS images on switches, firewalls and routers at work. I enjoy doing it and have been able to do so quickly and effeciently lately. It is one of those things you just need to practice on every now and then otherwise you start to forget how to do it.
Once I was finished with the upgrade I redid my crypto keys with the crypto key generate rsa command and chose 2048 bits for the crypto key.