Chapter 17. Case Studies: Implementing Switches

This chapter covers the following key topics:

• Real-World Design Issues This chapter presents an opportunity to apply the skills learned in earlier chapters in two real-world designs.

• Campus-Wide VLANs Considers the real-world downsides of flat earth designs.

• MLS Design Discusses and analyzes the pros and cons of a campus design that uses Multilayer Switching (MLS) for Layer 3 switching.

• Hardware-Based Routing Design Analyzes the benefits and unique characteristics of a campus design based on the Catalyst 8500-style of hardware-based routing.

• Configuration Examples Looks at actual configurations for two different campus designs.

Previous chapters have focused on building specific skills required to successfully understand and create scalable campus networks. This chapter steps back from specific campus skills and technologies to focus on the big picture.

In doing so, this chapter examines the design requirements for a rapidly growing campus network. To maximize the opportunity for analysis, two separate designs will be created for this single client requirement. Because of its proven advantages, both designs utilize Layer 3 switching in the distribution layer/Main Distribution Frame (MDF) devices. However, the first approach uses MLS to retain a distinct Layer 2 component at the distribution layer. The second design uses Catalyst 8500-style technology to create a hard Layer 3 barrier in the distribution layer.

Both designs also utilize a wide variety of other switching-related features. This presents a real-world environment where the pros and cons of different features and approaches can be discussed. Because, as a network designer, you are certain to face many of these same decisions, this chapter should serve as a useful template for your own campus designs.

Finally, do not focus on the specific products and models of equipment discussed in this chapter. Although the chapter mentions various products in an effort to be as precise and real world as possible, the main focus should be on campus design thought processes and methodologies. Although products are guaranteed to change at an ever-faster pace, the hallmarks of a good design rarely change (furthermore, the syntax shown in the configuration examples included in this chapter also rarely change signficantly).