Chapter 2. Segmenting LANs

This chapter covers the following key topics:

• Why Segment LANs? Discusses motivations for segmenting LANs and the disadvantages of not segmenting.

• Segmenting LANS with Repeaters Discusses the purpose, benefits, and limitations of repeaters in LANs.

• Segmenting LANS with Bridges Discusses how bridges create collision domains and extend networks. As the foundational technology for LAN switches, this section describes the benefits and limitations of bridges.

• Segmenting LANS with Routers Discusses how routers create broadcast domains by limiting the distribution of broadcast frames.

• Segmenting LANS with Switches Discusses the differences between bridges and switches, and how switches create broadcast domains differently from routers.

As corporations grow, network administrators find themselves deep in frustration. Management wants more users on the network, whereas users want more bandwidth. To further confuse the issue, finances often conflict with the two objectives, effectively limiting options. Although this book cannot help with the last issue, it can help clarify what technology options exist to increase the number of users served while enhancing the available bandwidth in the system. Network engineers building LAN infrastructures can choose from many internetworking devices to extend networks: repeaters, bridges, routers, and switches. Each component serves specific roles and has utility when properly deployed. Engineers often exhibit some confusion about which component to use for various network configurations. A good understanding of how these devices manipulate collision and broadcast domains helps the network engineer to make intelligent choices. Further, by understanding these elements, discussions in later chapters about collision and broadcast domains have a clearer context.

This chapter, therefore, defines broadcast and collision domains and discusses the role of repeaters, bridges, routers, and switches in manipulating the domains. It also describes why network administrators segment LANs, and how these devices facilitate segmentation.