Unlike some vendors, Cisco has a few different options when it comes to studying — and more importantly — labbing/practicing the hands on of what we’ve studied. Below are some options you can use for this…
Level: Great for CCENT or CCNAers
Its a really basic simulation software. Being sim, its not the real thing, so some commands may be missing or if you try to go too crazy with the topology it wont work as it would with real gear. I’ve never used it so I can’t say much on it, but its a good start for someone studying.
Level: CCNA, CCNP, CCIE R&S and Security tracks
Alot better than Packet Tracer, but has some hardware resources that you need (good CPU and RAM) in order to run the app. Unlike Packet Tracer, this guy lets you emulate the actual IOS so its the real deal. Unfortunately, switching is really limited and some thing in GNS3 “break” or don’t behave normally, but its the best thing next to real gear. GNS3 also let you now emulate ASA 5520 8.3+ code, so you can make ASA labs as well!
The devs at GNS3 have started integrating IOU into their app. Now you can use Cisco’s IOU product along with GNS3. This lets you now do switching. As of right now the 1.0 code is still testing so its not out officially yet.
Cisco’s internal app that lets you do pretty much anything, minus a couple of limitations. For Cisco employees only.
Boson Network Simulator
Boson is a 3rd party vendor that is similar to packet tracer but is geared towards people studying for their exams.