Each CCNA exam topic has an article dedicated to it on this website with some or all of the following:
- An overview of the technology
- Study notes - bold notes are must know material
- Packet Tracer and GNS3 lab files you can download and run
- Videos explaining the technology and configuration walk-throughs
- Links to reading material
- And my two cents (optional whether you take it or not!)
Whether you progress through this site lesson by lesson or you jump around to the topics where you need a refresher, at some point you'll want to get hands on configuring equipment. I have found that Packet Tracer works best for switching configurations and GNS3 works best for routing configurations. I don't recommend buying equipment to build a lab for the CCNA because it can quickly get expensive and today you can do everything you need to in Packet Tracer and GNS3. Read more about each below.
Packet Tracer is a simulation tool designed by Cisco that lets you create network topologies. I have found it to be really good for simulating a switching environment. I prefer GNS3 for mocking up routed networks because Packet Tracer has a limited command set, meaning it is not possible to practice all of the IOS commands that might be required.
Packet Tracer is very easy to download and install. Simply follow these steps:
- Go to the netacad.com website
- Click "Enroll to download Packet Tracer"
- Click "Sign up today!"
- Enter any information in the mandatory fields and click "Create Account"
- Close the popup that says "Launch Course"
- Scroll to the bottom of the page
- Click "Packet Tracer - Access resources on installing and using this learning tool."
- Download and install the appropriate version
Graphical Network Simulator-3 (GNS3) is awesome for mocking up and testing networks. While the S in GNS3 stands for simulator, it's actually an emulator. Read more below on the difference. The main point is that you can use this emulation software to create complex networks. Typically, I use it for testing routed networks since its support of layer 2 switching is less intuitive and I like to share my network files on this site. One nice feature it does have is the ability to combine virtual and real devices. So technically you can combine a layer 3 routing environment in GNS3 with a layer2 switching environment in Packet Tracer.
One other thing to mention with GNS3 is that you have to provide your own Cisco IOS for each device you're emulating. I think this is a very real challenge for anyone who is just starting out. The way I initially obtained my IOS images was to purchase used equipment on eBay and reuse the IOS image in GNS3. Once I had a certification and worked for a Cisco partner I had access to more IOS images since we supported them, which meant I could import them into GNS3. If you have found a legal workaround to this problem I'd be interested in how you did it. Please contact me and let me know.
In any case, GNS3 really is awesome. Unlike Packet Tracer with its somewhat limited command set, GNS3 has every command available. It acts just like a real router. If you can get past the initial hurdles of setting it up and finding IOS images for each device you want to run then it will prove to be a really good tool to have.
I have a few articles to help you get started with downloading and running GNS3.
Simulation versus Emulation
What's the difference between a simulator and an emulator? That's a good question. It's been asked multiple times on StackOverflow and Quora. Given our current context, Packet Tracer is a simulator and GNS3 is an emulator. Packet Tracer provides a lot of commands available to you, but not all, which means you can simulate many of the behaviors of a switch or a router, but the devices won't operate exactly like a real Cisco switch or router. GNS3 on the other hand is an emulator, which can duplicate the inner workings of a switch or router. GNS3 has all the commands available based on the IOS that you put on the device.
The issue is that the generic switch in GNS3 has very basic configuration options and no console access. If you want to configure a Cisco switch in GNS3 then you have to add a network module (NM-16ESW) to a router. While that works, it's harder to visualize when viewing a network diagram because your switch now looks like a router. That said, it's up to you whether it's worth having a full command set at your disposal over a partial command set that may or may not accomplish your objectives, but has an accurate network diagram.