The first time I heard about GNS3 was when I had started my CCNP training. I had previously worked on actual Cisco gear.
However, most of my Cisco gear was pretty low end and did not support the new commands. And being a student I could not afford to purchase new devices. So a friend of mine suggested me about GNS3 and that perhaps brought a total renaissance in my Networking studies. The money that I might have needed for getting new devices was invested in my CCIE training.
All I needed was a powerful processor, getting which was not a big deal (at least when you compare with actual Cisco gear!!!). And I could use over 20 routers at a time (Imagine purchasing those many actual routers !!!!!!!!!).
So, I did not have to worry about the hardware, just the concepts.
Thanks to GNS3, I successfully achieved my CCIE - Routing and Switching.
Here is a blog I'm working on. Anyone interested can benefit from it.http://tejasjain1991.blogspot.in