I guess a key part to studying for CCIE is to understand what devices and IOS versions you will be tested on in the lab. Thanks to Cisco they let you know this information;

Version 4 makes use of;

You may say that IOS is IOS and a router is a router, this can be far from true!

This is a Cisco 1841.

This is a Cisco 3825

These are some of the Cisco 3560’s