With IOS 15.x and the new ISR2 Routers, Cisco changed from a license based on the IOS Package to an universal image where the customer has to activate more advanced features with a license obtained from the Cisco site. Before we were able, even though without any support from Cisco, to download every image to get the needed features. While this is/was something bad if done in a production network, this is/was the way most people I know, including myself, did get into Cisco hardware and learned our way through the different topics for the Certifications. No matter if this was done on real hardware or with Dynamips/Dynagen/GNS3, it was a way to learn the stuff without having to spend thousands of dollars to get all features needed for the Certifications.
Now with the new license model, this is not possible any more (at least at the moment), if I lets say need to get into L2TPv3 I need to additionally buy the DATA License which has a list price of $1’000 for a CISCO3900 router! If they stay on that license route and don’t offer options for educational practice it will get hard to learn new (or refresh) things on your own.
Greg Ferro from Etherealmind.com did (re-)start a petition for an educational IOS license, if you’re in the same boat I’d suggest to visit his blog and sign the Petition: http://etherealmind.com/cisco-ios-petition-reloaded/