Upgrading and Repairing Networks

Chapter 52. Upgrading from Bridges and Hubs to Routers and Switches

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

Growing Beyond a Small LAN 974

From Bridges to Routers 977

From Bridges to Switches 981

You can use many kinds of network devices to expand a local area network (LAN) or to connect it to a wide area network (WAN). They range from simple repeaters to devices with more intelligence, such as bridges, routers, and switches. For the most part, traditional bridges have been replaced with switches. Both segregate network traffic to specific ports, but switches do so on a computer-by-computer basis, whereas traditional bridges do so based on LAN segments.

As a small LAN grew in the past, it was common to use bridges to segment a few small workgroups. Bridges were used to isolate local traffic among groups of users and thus cut down on the overall traffic on the LAN. However, depending on the kind of network (for example, ARCnet, Ethernet, or Token-Ring), there are limits to how many bridges (repeaters) could be used in a LAN. In addition to their usefulness in solving network traffic congestion problems, you can use routers or switches to solve several other problems: expanding the LAN beyond the size that bridges allow and connecting the LAN to other LANs to create a larger local network, or for a connection to a WAN, such as the Internet. In short, switches and routers offer the following benefits:

• Switches enable you to expand the LAN because they greatly limit the collision domain and switch traffic from one port to another, avoiding broadcasting packets unnecessarily on ports that don't have a route to the packet's destination.

• Routers enable you to connect to a much larger collection of networks, such as the Internet, and enable you to organize a large LAN into a hierarchical address space and many subnets.

	You can find out more about how routers and switches function by reading Chapter 8, "Network Switches," and Chapter 10, "Routers."

A traditional bridge has just about outlived its usefulness in a modern network. Instead, switches (which are really glorified multiple bridges all in one box) and routers can be used to better segment a LAN and limit unnecessary network traffic on local LAN segments.

In this chapter, the possibilities offered by upgrading to switches and routers are discussed, along with information you must consider when bringing such devices into your LAN.