Cisco Catalyst LAN Switching
This chapter covers the following key topics:
Layer 3 Switching Terminology Examines the confusing subject of Layer 3 switching terminology and jargon.
The Importance of Routing Discusses how routing, and therefore Layer 3 switching, is the key to building large-scale networks that are stable and easy to manage.
Router-on-a-Stick This section explores the use of traditional router platforms for inter-VLAN routing. As the earliest form of Layer 3 switching, this approach can use either multiple interfaces or a single interface configured for a trunking protocol such as ISL or 802.1Q.
The RSM Cisco's route-switch module was a natural evolution of the router-on-a-stick approach by bringing the routing function into the Catalyst 5000 chassis. This section discusses issues such as RSM configuration and the advantages of their use.
Routing Switches Explores the use of the NetFlow Feature Cards (NFFCs) to provide high-performance, ASIC-based Layer 3 switching. After a detailed examination of the theory behind MLS, this section also considers configuration and the appropriate use of MLS technology.
Switching Routers Discusses an alternate approach to Layer 3 switching represented by devices such as the Catalyst 8500. Resembling traditional router platforms from a design and configuration standpoint, the technology and configuration behind this approach is explained.
Routing Switches versus Switching Routers Although both styles of Layer 3 switching offer high-performance routing, they are very different from a design and implementation standpoint. This section takes a detailed look at these differences.
Catalyst 6000 Layer 3 Switching Examines how the Catalyst 6000 both evolves and blends the various Layer 3 switching technologies introduced before it.
HSRP This section discusses the use of Cisco's Hot Standby Router Protocol for both resiliency and performance.
Integration between Routing and Bridging Looks at several technologies that are available for blending Layer 2 and Layer 3 technologies.
Layer 3 switching is one of the most important but over-hyped technologies of recent memory. On one hand, vendors have created a labyrinth of names, architectures, and options that have done little but confuse people. On the other hand, Layer 3 switching (routing) is one of the most important ingredients in a successful campus design. While providing the bandwidth necessary to build modern campus backbones, it also provides the scalability necessary for growth and ease of maintenance.
The goal of this chapter is to clear up any confusion created by competing marchitectures (marketing architectures). By digging into the details behind Cisco's approach to Layer 3 switching, myth and fact can be separated. The chapter takes a chronological look at inter-VLAN (VLAN) routing. It begins with a brief discussion of switching terminology and the importance of routing. It then dives into the first technique commonly used to connect virtual LANs (VLANs) in a switched environment: the router-on-a-stick design. The chapter then looks at more integrated approaches such as the Catalyst Route Switch Module (RSM), followed by a discussion of two hardware-based approaches to Layer 3 switching. The chapter concludes with coverage of Cisco's Hot Standby Router Protocol (HSRP) and bridging between VLANs.