There’s nothing better than a router sim that has the full Cisco command set available to utilise. All of the router sims (up to now) have a stripped down collection of commands to use.
I stumbled on this website a few weeks ago. It’s an open source product that runs on Windows and Linux boxes, and enables you to simulate multiple routers on the one PC. You can even route real traffic out the ethernet interface of your PC, which takes it past the traditional ‘router sim’ that I am used to. The good thing is that this software supports multiple Cisco routers so it would be perfect for a budding CCNA, CCNP.
I have not tried it as yet as I’m building a PC specifically for this, but a friend of mine told me you need a pretty good PC with a Gig of RAM to make it worthwhile. He runs six instances/routers on his PC.
I would be interested in anyone that has tried this and what their thoughts are.