So you're thinking about getting your CCNA (Cisco Certified Network Associate) and you've heard how difficult it can be. I've recently begun my quest to ensnare this coveted title and thought it would be helpful to document my findings. What you will find in this series is not a how-to on the actual CCNA testing. Nor will this be a series to educate you on the basics (or not-so-basics) of using Cisco equipment (more on that later). What I hope to accomplish is to enlighten you on what you need going in, what you should focus on while you're in (classes), and what you should work on when you're out. With this knowledge (combined with the technical information you take away from class), you'll be on the short road to the CCNA.
With Cisco (as with most in-depth certifications), there are certain skill sets you should have. These skills not only hold your key to success on the CCNA exam but also determine your worth as a network administrator. Because of this, you will do well to take to heart the following advice.
Even before you go into your first CCNA class, there are certain skills you should know and know well. The first is TCP/IP fundamentals. Not only is this skill set one-third of the CCNA exam, it is critical to your IT career. How familiar should you be with TCP/IP fundamentals? Obviously, with Cisco technology, you are working with the backbone of networking. You need to know what is empowering the data you are attempting to route, block, share, and kill.
Prior to going into the CCNA classes, it is crucial that you have a working knowledge of a few key elements of TCP/IP. Outside of these key elements, you should be able to pick up the rest during or after (preferably after) your class.
OSI layer model
The OSI (Open Systems Interconnection) network layer model is a critical factor in your understanding of networking. As you look at the OSI model, you may think that it is as simple as memorizing the layer names and which function is associated with each layer. This is not so. With only a memorized list of the layered model, you very well may find yourself struggling to plug the Cisco pieces into the puzzle.
So, instead of a memorized list of the OSI networking model, you should go into your class with an understanding of the following:
- Specific definitions of each layer
- How the various layers interact with each other
- How a piece of data travels along the model to finally become a series of ones and zeros capable of traveling your network (encapsulation)
- Which piece of technology (i.e., hardware) works in conjunction with which layer (i.e., Web browser with application layer)
- How the OSI model relates to the Department of Defense model
This topic will be the one that takes the most down. Let's face it—this will be the bulk of your work. In order to get through the CCNA classes with a less-than-migraine feeling, you should enter with a good understanding of how IP addressing works.
With a solid IP foundation, you will not get bogged down on working out the subnetting questions, you won't sit in a deer-in-the-headlights trance as the instructor speaks of broadcast and collision domains, and you'll be able to (at least) concentrate on how this all affects Cisco technology.
With that said, what should you know? Subnetting, subnetting, subnetting! Prior to entering your CCNA class, you should know how to subnet all types of networks (class A-C). You should know how to calculate a subnet ID, first and last valid host addresses, broadcast addresses, and subnet masks.
If you go into the CCNA class without this knowledge, you will find yourself falling far behind as you struggle with the concept of subnetting. It's not an easy skill to learn, and you certainly don't want to miss out on key information because your brain is still trying to construct that Class A subnet!
Obviously there are many roads that will lead you to an understanding of subnetting. Whatever road you choose, make sure it leads to a full understanding of how subnetting works, as well as the practical applications. What is a solid practical application of subnetting? Answer the following:
Write the subnet, broadcast address, and valid host ranges for the following:
- 172.16.10.5 255.255.255.128
- 10.10.10.4 255.255.255.192
If you have a Class B network address subnetted into 492 subnets, what subnet mask would you assign?
If you can answer the above questions, you're on the gold road to CCNA!
It's not all about the OSI layer model and IP addressing. One last skill you will want to take into CCNA classes is a familiarity with the command line interface. Knowing the ins and outs of entering commands, switches, and arguments from a prompt will make learning the Cisco IOS that much simpler. The issue here is that most people do not have ready access to Cisco equipment nor a working knowledge of how the command line is used. For this reason, getting used to the Cisco IOS (Internetworking Operating System) can be a burden.
How do you go about familiarizing yourself with the command line when you don't have access to a Cisco product? A convenient way to get accustomed to the command line interface is by using Linux. Here you can dive deep into the usage of the “prompt” without having to spend thousands of dollars on equipment.
With this Linux solution, you can enable a small machine to act as a router so you will also gain a working knowledge of how the infrastructure works. Also, you will not turn green when you see something like:
ipchains -v -A input -p UDP -i $OUTWARD_IF -s $ANYWHERE -d $LOCAL_IP 6770 -l -j DENY
Taking the CCNA plunge is not a task for just anyone. It takes a certain skill set and a high threshold for pain to pass this rather demanding exam. However, with plenty of preparation you can go into the class with more confidence and focus, and you'll find yourself more attuned to the facts and issues you need to make it through this task.
The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.
Jack Wallen is an award-winning writer for TechRepublic and Linux.com. He’s an avid promoter of open source and the voice of The Android Expert. For more news about Jack Wallen, visit his website jackwallen.com.