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Chapter 12
Network Design Review


ü Summarize the major concepts covered in this class.
ü Recall the steps for internetwork design.
ü Describe methods for monitoring your internetwork design.
ü Return to your environment with fresh ideas and plans for internetwork designs.

The other day I came across an e-mail thread that discussed a 10-year-old boy who has passed a number of the Cisco exams and attained CCNP certification. While I certainly applaud his efforts and initiative (though I do question the authenticity of the report), it compelled me to think about this chapter specifically. The authors, editors, and publishers of these Study Guides and related books strive to provide readers with the information needed to pass more than a certification exam. While all of the material in this book is geared toward the CID exam objectives, it is not our intent to provide the answers. To do so would diminish the certification process. Quite frankly, the exams cover only a small fraction of the material that you need to succeed in this field.

In the majority of books related to exams and certification, it is stressed that real world experience is a must. This is very true, although the topic of design does migrate toward the theoretical. However, it helps to have the practical knowledge to apply and understand the concepts. Having said that, I encourage readers who don’t work on production networks daily to seek out a mentor who can share configurations and diagrams before they attempt the exam. Frequently, the mentoring process is educational for both participants; the effort helps to fill in gaps in the learning process.

You will find that the majority of the items discussed in this chapter are familiar—hopefully because you have experience in your own network. This chapter is significantly less formal than the previous chapters and reflects upon the material in this book much in the same way that the objectives reflect the classroom experience. In fact, it is likely that you are using this book as part of a formal lecture, which should aid in integrating this material.

Back to the young man who became certified. If permitted the soapbox for a moment, I’d like to stress to all readers the importance of knowing the nontechnical in addition to the technical aspects of internetwork design. It took years before I learned this important lesson. The best designers are not those who only pass the test. They are usually not the ones who know every nuance of the IOS. They are the ones who think outside the box or, as a friend once corrected me, outside the circle. He was right.

It is also important to hone skills unrelated to your field or desired field. For example, the chief of the Seminole tribe in Florida brought in casino gambling a few years ago, and with this came new jobs and added income. The money was used to diversify into non-gambling markets, and recently the tribe purchased an aircraft manufacturer. The plane will be called the Micco, after the chief’s son.

How does this relate to network design? It doesn’t. It relates to skills and diversity. The chief knows that he and his family will have enough money and that their son will learn the business skills used by his father—skills that will help make his son successful, too. However, in a 1999 interview, the chief noted that when his son is old enough he will teach him alligator wrestling, a dangerous sport, to say the least. The chief’s rationale: “ I’ll catch a ’gator for him to wrestle at some point, so he’ll have a skill he can keep in his hip pocket. So, when all else goes wrong, he can find a ’gator and make a few dollars off of it.” In network design, that hip pocket may include marketing, sales, or any other business or non-business focus. Communication and interaction skills will be increasingly important in the future as well. My final point: Some headhunter and career-planning studies report that workers will have up to eight different careers in their lifetime. Thus, flexibility is important in both career planning and in the singular career of network design and administration.

So, as you read this chapter and reflect on the material presented throughout this book, take a moment and think about the application of it all. Consider taking a moment to go to lunch with the sales folks to learn about their business and how they use the network. Better yet, learn how they don’t use the network. Understanding why the network doesn’t meet the needs of the user community is critical to addressing those needs.

Major Concepts of the CID

Obviously, Cisco wrote their objectives in the context of the Internetworking course materials, and the applicability of a review is questionable in a static text. In the Cisco materials, the summary of the course typically receives a quick gloss-over and provides the instructor with the opportunity to address a running list of issues that have been identified during instruction. When this book is used as a training aid in a classroom setting, I recommend that you spend some time now to review the materials covered in the course.

In a static setting, such as when you are working by yourself, it would be opportune to flip through and look over any highlighting or other marks. It would be difficult to repeat all the material that might be needed at this phase. However, following is a list of those areas that are significant because they are either difficult or important. Do not view this list as comprehensive for passing the exam—it is not intended to be and it is not constructed based on the live exams. Simply use this list as a foundation for asking yourself if you understood this material.

  Know the various network design models, especially the hierarchical model.
  Feel comfortable with applying the material in this book in real-world situations. It might be beneficial to have a study buddy or group—ask each other how to apply this material.
  Understand VLSM and IP addressing.
  Be familiar with the capabilities of the IP routing protocols.
  Understand the benefits of AURP.
  Understand the benefits of NLSP.
  Know the characteristics of EIGRP in its three flavors.
  Know the components of ATM LANE.
  Understand the differences between ATM LANE and ATM PVCs.
  Understand remote connections, including control, node, and gateway.
  Understand Frame Relay, ISDN, and X.25.
  Understand the mainframe technologies, including RSRB and DLSW+.
  Know the characteristics of desktop protocols.
  Be familiar with the issues regarding Windows networking.
  Know the ways to secure a network.
  Review the CID exam objectives.

Overview of Network Design

Network design is many things. Typically, it accomplishes the following:

Implements cost-effective solutions. This requires that the design include both initial and recurring cost analysis. Designers need to consider scalability and adaptability in determining the cost effectiveness of their solutions as well.
Utilizes the best technologies It’s difficult to know what the best technologies will be in the future, yet at present the industry appears committed to IP, Ethernet, Frame Relay, and ATM. Future technologies will undoubtedly include wireless, DSL, Packet over SONET, Dynamic Packet Transport, and DWDM (dense wavelength division multiplexing). These technologies are here today. Soon, vendors will champion cutting-edge concepts based on current research, including the use of jellyfish for data storage and carrying IP packets on photons.
Consists of scalable designs Scalable designs are a must when considering resource and capital costs—if the network does not scale, it cannot support growth or new features. This will require replacement costs when the company’s needs grow.
Utilizes an easy-to-administer hierarchical model. The hierarchical model simplifies the incorporation of scalability in the design. It also improves diagnostic processes.
Provides redundancy and integrates other methods to reduce downtime. Depending on the business demands, the network may require redundancy and fault tolerance, especially in financial and other real-time environments. However, the costs associated with downtime (based on per minute, per salary, per person) can become very high, even without a direct customer interface. Since some redundancy can be incorporated at low or no cost, it should be included in any design.
Meets or exceeds the customer’s business and technical requirements. It is hard to fail when you surpass expectations. This goal should include anticipating needs, meeting the predefined objectives, and completing the project on time.

The best network designs result from a thorough planning phase in which all of these elements are addressed. This stage should result in a list of objectives that will be compared to the final result—refrain from determining the success of the project until you’ve met the initial objectives or improved upon them.

Designers should also note that sometimes these objectives will be mutually exclusive in the eyes of the business. For example, a redundant, hierarchical model may require more than double the funds compared to a sufficient design. A remote office with 20 workers and its own file and print services may not need redundant links—it depends on the business.

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