So I have been tooling around with a piece of software called dynamips/dynagen for a couple of years now. It is a two piece open source software package that emulates a Cisco routers motherboard. You can fire up a Cisco routers IOS and have full use of all the services and commands. I see the future of Cisco training going down this virtualization path. You can setup multiple routers with serial and Ethernet connections in between. Basically a full stack of equipment, I am currently using it to study up for my Cisco CCIE R&S lab. Yes it is that functional! For Cisco CCNA training it will be tremendously useful, for the Cisco CCENT perhaps not so much because Cisco CCENT certification is more along the lines of theory where as CCNA and the CCNP are more practical/hands on in nature.