Network Design and CCDE by Mark Holm

Getting your mind set on virtually any Cisco certification requires you to carefully consider your options and possible paths to ultimately reach your goal. This includes, but is of course not limited to, activities such as examining the official blueprint (I highly recommend printing it so you have a copy at hand, by the way), compiling a list of books and other relevant training material and so on.





What CCDE is…

Preparing for the CCDE is no different from other exams or certifications in terms of building a list of the initial materials, but during your preparation you will likely come across one major subject that makes CCDE stand out a bit when compared to most other Cisco certifications: you must be able to determine when and how to use a certain technology in a given situation. In context of the CCDE Practical Exam, this is given to you as a set of requirements and constraints that you must use to determine which choice is correct. When sitting for the CCDE Practical exam, you will have all the required information available to you. There’s no need to make assumptions here which (based on personal experience) may be the case in your real-world design tasks or assignments. Simply put, your job is to put the pieces of the puzzle together and connect the dots.


When you prepare for the CCDE exam, you need to learn how to scan the available information for key points you will need to solve a given task which may also include learning how to determine whether some pieces of relevant or related information are missing.  During the CCDE Practical exam, this involves translating the information presented to you into relevant technologies that live up to all the requirements, demands, expectations, and constraints, all of which will be presented to you as part of the scenario.


If you are an active CCIE or have attempted the CCIE lab exam, you need to be aware that you need a different skill and mindset if you are going for the CCDE. Even though both certifications require a deep technical understanding of both technologies and protocols, there are still a lot of differences you need to be aware of.


As a CCIE candidate, you need to be able to implement or troubleshoot a certain technology or protocol within a given set of restrictions and requirements, whereas the CCDE focuses on choosing the correct technology or protocol for a given situation based on a series of requirements or how it operates in a certain context. While a CCIE candidate likely knows all about how to fine-tune and tweak IS-IS it may not necessarily be the right approach from a design perspective. You shouldn’t just drill down on a specific technology and optimize away – what you do isolated to IS-IS may have negative side effects for other technologies of your design, and may even steal focus from the bigger picture.


A network designer does not necessarily know all the implementation details (if any at all) instead, focus should be at a higher level, where you need to be able to see the bigger picture and make sure all components play well together.


A note on technology and design

Of course, the CCDE needs extensive knowledge around the different areas and topics which may translate directly into reading being the primary activity of your studies. Making various practical labs is also a good way of learning, but keep in mind that you should not spend hours and hours on the implementation details – once you have a firm understanding on how a certain technology works, you can move on to the next topic. In my own CCDE preparations, I did not do any labs as part of my preparations. My primary study method was reading all the relevant material I could find (see links below).


At this point, your experience comes into play as well. Besides learning the theory behind a technology, chances are that you have already worked with it, perhaps at an implementation/operations level. During those times, you have likely learned a thing or two, which may come in handy when you start looking at things from a design perspective. Network design is not necessarily an exact science as such. In real life, some design decisions might be based on personal preference rather than pure theory and best practices. If you for instance know that OSPF works great in a given situation/topology, it is more than likely that you will choose OSPF again in the future if you come across identical design challenges. While that is perfectly valid (experience wins over theory, right?), keep in mind that other technologies may have emerged and others may provide new functionality – what you’ve done in the past may not be the best choice tomorrow.


A good network designer should always be aware of several options that can solve the task at hand. This helps to ensure that the final design choice is based on a comparison of pros and cons of the possible solutions, leading to an optimal design. Following your experience alone might not lead to the optimal solution – but never forget to use the experience you have gained over time. You need to find a balance between using your experience and your knowledge in your designs. This is not per se an easy task to perform, but with your experience and some of the CCDE methodologies in your toolbox, you stand a good chance of getting it just right.


A CCDE in the real world

In the real world, you are more than likely to face the same challenges in terms of having to choose a certain technology over another, but there is a good chance that you may not have the luxury of having all the cards laid out on the table in front of you.


More likely, you will often find yourself digging out important pieces of information yourself, and from time to time you will be put in situations where you need to make assumptions. The problem with assumptions is just that – they are assumptions, so they can be right or they can be wrong. A wrong assumption may hit you like a boomerang, just when you thought everything in your project was going as smooth as it could go. It might just result in a small bump in the road, but it can also turn out to be even more than that, possibly requiring a re-design of certain parts or even the whole project. The big thing here is obviously how to minimize (preferably eliminating it entirely, but I doubt that will ever happen…) the amount of assumptions you need to make. And just how can you do that? There’s no exact answer to that question, but from my point of view and experience there are a few key items to consider:

  • Make sure you know all requirements, demands, expectations, and constraints. These are the foundation of any design project. Having to make assumptions at this stage of the process should result in a re-evaluation of the project and its scope.
  • Don’t be afraid to ask questions if something is unclear to you. It is your responsibility as a network designer to make sure all relevant information is available to you in due time, so you don’t have to make assumptions because someone forgot to give you some of the details.
  • Determine which questions you need to ask. Go through all the information you have at hand and try to build a mental, holistic view of it. Look for obvious missing parts of information.
  • Ask questions to the right set of people. Make sure you know who will be able to give you answers with the information you are looking for. If the information received seems to be too “light” or you get answers that you find non-adequate or lacking detail, don’t be afraid to ask the question again. Make sure that the people you ask the questions don’t assume you know or already have a certain piece of information.
  • Use your experience. Over time you will be able to spot the issues or areas that most people seem to forget or assume. Things like the amount of bandwidth at remote sites, which QoS classes that are available with the MPLS Service Provider, and application requirements just to name a few. The thing to notice here is that this information is often just taken for granted, so it is not left out deliberately. People just don’t think of it because it is often not a concern.


While experience obviously can’t be taught, most of the other aspects can. You also need to continuously build on your knowledge of technologies and protocols to make sure you stay up-to-date. For example, networks built on overlay technologies (for instance Cisco ACI which uses VXLAN internally) are gaining traction and increased popularity because of their scalability while allowing key features such as Layer 2 mobility. As a network designer, you should be aware of those trends and incorporate them into your designs whenever they are relevant for the project you are working on. This is expected from you.


The following are some of the key points on acting as a network designer in the real world that I’d like to highlight. They are also somewhat relevant in context of the CCDE Practical exam.

  • Know your technologies and protocols and how to make use of them. It is vital to keep yourself up-to-date with industry trends and new inventions and evolution, allowing you to develop up-to-date network designs. This does in no way mean you should use a new technology just because it is out there, but you need to be aware of it and know it well enough, so you know when and how to use it in your designs.
  • Be aware of current best practices when developing a network design. There’s no need to re-invent the wheel. Use well established programs such as Cisco Validated Designs as a foundation, but remember that these are not the answer to every challenge. They are generic in nature and may need to be personalized/adjusted to live up to all the requirements given by the project they are to be used in.
  • Make use of your experience. Keep building on it and continuously develop your experience too. You need to produce up-to-date network designs by finding the right balance between the well-known solutions you know to work and the on-going evolution.
  • Think big. With things such as IoT coming right at us, we need to be able to develop even bigger and more scalable networks in the future. With a CCDE badge attached to you, you will have the foundation to be a part of that.


CCDE – a different breed

Personally, I found CCDE to be quite challenging. My preparation was significantly different as compared to the preparation I did for the CCIE lab exams. As I mentioned earlier, doing tons of practical labs doesn’t necessarily make sense in context of the CCDE, but it depends on the type of person you are and how you tend to learn best.


Some of the most important skills I’ve learned on my CCDE journey are:

  • Knowing how to map/translate business requirements into relevant technologies that support these requirements.
  • Being able to spot optimization potential and low-hanging fruit on the go.
  • The ability to analyze documents and spot relevant information quickly, while filtering out irrelevant or extraneous information.
  • Seeing things in a bigger perspective and avoid focusing on details in a certain area of the project.
  • Taking a different view on the protocols and technologies I already knew from my CCIE experience. You simply need to look at them from a different perspective.
  • Having a toolbox as to how to stitch it all together without losing the big picture. This toolbox seems to be of an unlimited size and will grow with your experience and career.


The list is not exhaustive in any way – it is just the ones that I’ve listed here I find to be of most value to me.


With network design being a subjective topic by nature, it is a good idea to discuss your understanding and design aspects of a certain topic with peers and/or in study groups. Your perception and understanding of the topic(s) may be different from those of the members of your study group. From personal experience, these discussions are likely to provide you with new information or other views on the topic(s), allowing you to see things from a different perspective. At the end of the day, these discussions are what will allow you to develop yourself both technically and also in terms of seeing things from a different perspective. Therefore, a key activity in CCDE preparation is to participate in study groups where you can have those kinds of discussions. There are lot of different communities and offerings out there.  Search around and find one that suits you. Personally, I enjoyed the social aspect of this too and I believe that this is not something you should overlook.


When preparing for CCDE (and just being a network designer in general, in fact), you will learn that you should look at technologies differently than you would do with a non-design oriented certification. You should always attempt to maintain a holistic view and try not to focus too much on the implementation aspects. If you, like me, come from network engineering background, this can prove to be an incredibly difficult task, because that’s exactly what you have been doing in your career so far. My best advice is to attempt not to convert everything into configuration statements in your head (I did that a lot – and still do…). Stop right at the point where you have the answer to the “what” and “why” questions – do not go down into the how questions, no matter how interesting they look. This is one of the big differences between the mindsets of a CCIE and a CCDE candidate – if you apply a CCIE mindset to a CCDE candidate and a CCDE mindset to a CCIE candidate, my guess is that the probability of both failing is quite high.


The good thing about mindsets is that you can learn different ones and use them when you need to – and that ability is likely what will stand between you and success in your CCDE journey!


There’s a good chance of you learning a thing or two about yourself on the path towards the CCDE. You might have to look at things differently, take a different approach on certain things or think out-of-the-box. In my world, this counts as personal development, which could benefit you in other situations than just in a CCDE context, and that is always worth the efforts in my opinion. Don’t miss out on that either!


About the Author

pic Mark Holm.jpg


Mark Holm, 3xCCIE #34763/CCDE #20160020, is a Network System Engineer with Conecto, always focusing on designing scalable network solutions that fully meets customer expectations and requirements, no matter whether these networks are Campus networks, Service Provider networks or Data Centers.

Mark is often used as a SME due to his extensive knowledge in most aspects of networking, and is an active contributor to the Cisco certification community.



Here are a few additional ways for us to engage and keep the conversation going: