I remember seeing a free one somewhere.. or a demo.. check
they might have one.. though they usually only let you stay in user mode.. no enable. If you're studying for a certification I would strongly suggest you spend a little bit of money to get yourself a good one like Boson Router Simulator.. especially if you haven't had much hands on experience with a router. Think about it, you're already spending on the exam, you may as well shell out a bit more.
Give me a couple of days and there will be some software to download from my web site
, or since i am new here, could you tell me where i could upload it to? I am a CCAI [cisco certified academic instructor] so i get access to some cool stuff...