Foreword

Foreword

With the advent of switching technology and specifically the enormously successful Catalyst Switching products from Cisco Systems, corporations all over the world are upgrading their infrastructures to enable their networks for high bandwidth applications. Although the original goal of most switched network design was primarily increased bandwidth, the networks of today require much more with the advent of mission critical applications and IP Voice emerging as mainstream networking requirements. It is therefore important not only to reap the bandwidth benefits of Catalyst switching but also learn sound network design principles leveraging all of the features in the Catalyst software suite.

One thing network designers have learned over the years is that things never get any easier when it comes to understanding and evaluating all of the available technologies that appear in standards bodies and are written about in trade magazines. We read about MPOA, LANE, Gigabit Ethernet, 802.1Q, 802.1p, Layer 3 switching, OSPF, BGP, VPN, MPLS, and many others. The key, however, to building and operating a successful network is understanding the basic fundamentals of the relevant technologies, knowing where and how to apply them most effectively in a network, and most importantly leveraging the successes of others to streamline the deployment of the network. Internetworking design is part art and part science mostly due to the fact that the applications that ride on top of the network have widely varying traffic characteristics. This represents another challenge when designing a network because you might well optimize it to perform for a certain application only to find that a few months later a brand new application places entirely differing demands on the network.

The science part of campus network design relies on a few basic principles. First, every user connects to a port on a switch and so wiring closets are provisioned with Catalyst switches such as the Catalyst 5000 family to connect end users either at 10 megabit Ethernet or increasingly 100 megabit Ethernet. The base level of switching capability here is called Layer 2 switching.

There are typically tens to hundreds of wiring closets that need to be connected somehow. Although there are many ways to do this, experience has taught us that a structured approach with some hierarchy is the best technique for a stable and easily expandable network. Wiring closets then are typically consolidated into a network layer called the distribution layer that is characterized by a combination of Layer 2 and Layer 3 switching.

If the network is large in size, there can still be a large number of distribution layer switches, and so in keeping with the structured methodology, another layer is used to network the distribution layer together. Often called the core of the network, a number of technologies can be used, typified by ATM, Gigabit Ethernet, and Layer 3 switching.

This probably sounds rather simple at this point, however as you can see from the thickness of this book, there is plenty of art (and a lot more science) toward making your design into a highly available, easy to manage, expandable, easy to troubleshoot network and preparing you with a solid foundation for new emerging applications.

This book not only covers the science part of networking in great detail in the early chapters, but more importantly deals with real-world experience in the implementation of networks using Catalyst products. The book's authors not only teach this material in training classes but also have to prove that they can make the network work at customer sites. This invaluable experience is captured throughout the book. Reading these tips carefully can save you countless hours of time experimenting on finding the best way to fine tune your particular network. In addition, as part of the CCIE Professional Development series of Cisco Press, you can use the experience gained from reading and understanding this book to prepare for one of the most sought after professional certifications in the industry.

Stuart Hamilton, CCIE #1282

Senior Manager, Enterprise Network Design

Cisco Systems Inc.