In the past, whether you're studying for CCNA, CCNP or CCIE, you need Cisco equipments for lab practice. However not everyone has the chance of playing around with the real equipment, unless you're working as a Cisco vendor or end user with spare equipments. Some of them might rely on the Boson's router simulator, which is just a simulator. It's programmed in such that limited functions can only be performed.
A few years back, Dynamips, which is a Cisco router emulator program was written by Christophe Fillot to emulate Cisco routers. The front-end software such as
Dynagen can be used to configure and provision Dynamips emulator networks. Cisco engineers now can use such wonderful software to emulate Cisco lab with the desired network topology without having to use any real equipments.
I'm currently using Dynagen for my CCIE Service Provider lab practice. My pathetic Intel Duo Core 1.78GHz (2GB RAM) company laptop is able to emulate about 8 routers, while my Intel Core2Duo 2.13GHz (2GB RAM) desktop is able to emulate about 10 routers, both with simple MPLS VPN services. In order to run the full lab topology, I need a CPU which allows me to emulate 14 routers. Alternatively, I'm running multiserver Dynagen, distributing the processor power over my laptop and my desktop (7 routers each). As long as there is a Layer 3 connection between the two PCs, it should be fine. In my case, it's running over home wireless.
Now I just can't wait to buy the Core i7 and run the lab smoothly.