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The exam consists of 85 questions (the test will tell you 88, but I got 85), most of which are multiple choice. Some of these questions may be, for lack of a better term, of the "drag and drop" variety. For drag and drop questions you drag boxes from one side of a page and place them where you think they belong on the other side of the page. Most have a story problem about a company that requires a WAN. Your job: to figure out the best way to design this WAN. The really nice thing about it is that the story questions always feature the same companies (I learned about two in my version of the test), so you don’t have to digest a completely new story every time. Some questions will require you to be able to read network diagrams as well, so get a copy of Visio (or equivalent) and start playing around.

One challenge: At the time of this writing, Cisco hadn’t publish the exam objectives for the DCN test. The company promises to remedy this situation soon, but in the meantime, you won’t know what the test is about or what to expect when you take it. That’s what this article is for, to let you know what to expect and what to study if you wish to hold the grand title of CCDA.

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Know Thy Routed Protocols…

To successfully pass the CCDA exam, you’ll need a good working knowledge of the protocols used to create an enterprise internetwork, starting with the routed protocols. Probably the most important routed protocol in today’s internetworks is TCP/IP. Know how it works. One very important topic for you to understand is the difference between classful and classless addressing. Many networking professionals today are used to using the subnet masks required by classful subnetting, whereas you need to understand the prefixes that are used with classless addressing and why they’re used.

You also need a solid understanding of each of the protocols in the TCP/IP stack. You should know where each protocol resides and what it’s designed to accomplish. For example, do you know the difference between TCP and UDP? Do you know what protocols in the stack reside at OSI layer 3 of the stack? Not that these questions will get you through the exam, but it’s a good example of the kind of knowledge you need to have about TCP/IP.

In fact, that kind of knowledge will help you with all of the routed protocols. You won’t have nearly as many questions about IPX or AppleTalk as you do about TCP/IP, but they’ll be there so study them. You should know where the protocols reside in the stack and what they’re for. You should understand, for example, what IPX does and where DDP resides in the OSI model. Don’t forget SNA either, since there are so many mainframe networks in the world today.

Not only should you understand how these protocols work by themselves to form a LAN, but how they work together to form a vLAN. A virtual LAN may be just the thing you need to make your routed protocols perform the way you want them to. A solid understanding of these types of things will help you get a passing score.

...And Thy Routing Protocols

Since you’ve read this far, chances are good that you know the difference between a routing and routed protocol, but do you know the difference between the various routing protocols? Expect to get quizzed on these; know which does what. Some of the knowledge you’re expected to hold is the difference between distance vector and link state and when each would be a desirable solution to a problem. Not only should you know the difference between the two types of protocols, but you should know which protocols fall into which class. For instance, is RIP distance vector or link state? OSPF? NLSP? RTMP? If you aren’t sure, study them.

Make sure you understand the differences between interior and exterior routing protocols. Do you know when to use an exterior as opposed to an interior routing protocol? Do you know which protocols are interior and which are exterior?

Put WAN Protocols on That List Too

Besides routing and routed protocols, others exist to make up a WAN. A solid understanding of the protocols that connect campus LANs together to make a WAN is a definite requirement.

One of the most important to understand is the tried and true Frame Relay protocol. Know where this sits in the OSI layer, what each of the protocols does, and how it works overall. Have a firm understanding of Frame Relay’s predecessor, X.25. You won’t go as deep on X.25 as on Frame Relay, but since the protocol is still available, it’s good to understand it.

Another protocol you need to become friends with is the ATM protocol. You need to know how this works and what it’s for. When, for instance, should you use ATM instead of Frame Relay? What are the various protocols associated with ATM? How can you use ATM on a LAN as well as a WAN? Studying questions like these will help you get a firm grasp of ATM.

A solid grasp of ISDN is also a requirement for a passing scored. You should know when to use ISDN and how it works. You should know the devices that are required to make an ISDN connection work and what services they provide, devices like the NT1 and the TA.

PPP is a good protocol for backups on a WAN. And xDSL can be used for backup connections as well as full-blown WAN connections, so don’t forget to study them.

The Hardware and Software

Since this is a Cisco exam, one would expect coverage of Cisco routers and switches. Make sure you understand the differences among a 1600, 2500, 400, and so on.

Cisco also has a number of software packages that are targeted to help you design and manage networks. You should have a basic understanding of such products as CiscoWorks, CiscoWorks Blue, StrataSphere and other Cisco software packages.

The ABCs of It

Not surprisingly, a large chunk of this test is based on your knowledge of industry acronyms and terminology. Things like ABR, NT1, QoS and a host of other acronyms will rear their ugly heads on the exam. Terms such as Area 0, Demilitarized Zone, Firewall, and Bastion Host could also show up. Be sure you have a good working knowledge of these and other industry terms and abbreviations before tackling the test

On Design

The most important part of this exam is the challenge of designing a network. You need to know the process for designing a scalable, robust internetwork that can stand the test of time. Many of us think we know exactly how to accomplish this. After all, we’ve been doing it for years, right? But there’s more to it than the obvious.

Networks should be designed hierarchically. Do you know the layers of the hierarchy and what they do? You need to understand the three layers of design—core, distribution, and access—and what purpose each serves, as well as how they work together to provide your end users with a WAN.

Know the steps to come up with this design as well. Form the RFP from the client, to the logical design phase, to the implementation phase, to the testing and documentation phases. There are specific steps in each phase that you need to understand if you want to provide your clients with a robust, scalable network.

How To Prepare

Currently, no books exist specifically for the CCDA exam. There are a few in the works—the one I eagerly await is Sybex’s CCDA Study Guide from Todd Lammle (he did a great job on the CCNA Study Guide). Also, Cisco Systems has a self-paced training kit available called Designing Cisco Networks, intended to prepare you to pass this exam; it’s priced at $400.

The best resource I found for preparing is Cisco Press’ book Top Down Network Design by Priscilla Oppenheimer. This book discusses everything that you need to know to pass the test and is a very good way to study for the exam. The only drawback: It’s a bit dry for my taste, very few analogies and very little humor. Don’t just read it either. A lot of us make that mistake when we get a book without hands-on exercises. Study this book and think about it. Especially read the case studies in the latter chapters. They look a lot like the ones you’ll find on the exam. Ms. Oppenheimer, if you’re reading: Thanks for the book—it really helped out.

I like using practice exams as part of my preparation regimen, so I scoured the Internet for just such a tool. The only one I could find (aside from the one that comes with the DCN course from Cisco) is a practice test from NetworkExams.com, so I thought I would give it a try. It turned out to be somewhat helpful. One of the problems is that it uses too much humor. Many of the questions had a frivolous answer associated with them, which didn’t represent the actual exam at all. Also, every time I passed the exam, it told me I had failed—annoying but not fatal. The practice exam also has some wrong answers (for instance, the test tells you that TFTP doesn’t work with UDP when, in fact, it does). A nice feature about the exam is that it lets you go back and review you answers and tells you what you got wrong and why they’re wrong.

Going for the Challenge

Overall, the exam is well done. It tests your knowledge and skill quite well. If you’re looking for a challenge in the networking industry, then you’ve found one in this exam. It’s difficult enough to test your mettle, but not so tough that you can’t pass it with the right preparation. This test will gain respect for you in your chosen field, so study hard and apply yourself to learning. You, too, will pass the trial of the CCDA.

You can contact Joseph about "The Trial of the CCDA" at editor@tcpmag.com.