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2012-05-29

A+: Switches and Hubs for LANs, Repeaters, Bridges, and Routers for WANs

Hubs connect different computers with each other on an Ethernet network based on UTP or STP cabling. A hub has several connectors for RJ45 cabling, a power source, and signal lights to indicate network activity. Most hubs are stackable, meaning that if you need more ports than the hub contains, you can connect it to another hub to expand its capabilities.

A hub is the slowest connection device on a network because it splits the bandwidth of the connection among all the computers connected to it. For example, a five-port 10/100 Ethernet hub divides the 100 Mbps speed of Fast Ethernet among the five ports, providing only 20 Mbps of bandwidth to each port for Fast Ethernet and 10/100 adapters, and only 2 Mbps per port for 10BASE-T adapters. A hub also broadcasts data to all computers connected to it.

A switch resembles a hub but creates a dedicated full-speed connection between the two computers that are communicating with each other. A five-port 10/100 switch, for example, provides the full 10 Mbps bandwidth to each port connected to a 10BASE-T card and a full 100 Mbps bandwidth to each port connected to a Fast Ethernet or 10/100 card. If the network adapters are configured to run in full-duplex mode and the switch supports full-duplex (most modern switches do), the Fast Ethernet bandwidth on the network is doubled to 200 Mbps, and the 10BASE-T bandwidth is doubled to 20 Mbps. Switches can be daisy-chained in a manner similar to stackable hubs, and there is no limit to the number of switches possible in a network. However, switches introduce delays in the network, or latency, as it takes time to compute where the packets should go.

Beyond LANs— WANs

Windows since XP features built-in bridging capabilities. You can also use a wireless router with a built-in switch to create a single network with both wired and wireless clients.

Hubs and switches are the only connectivity equipment needed for a workgroup LAN. However, if the network needs to span longer distances than those supported by the network cabling in use or needs to connect to another network, additional connectivity equipment is needed.

• Repeater—A repeater boosts signal strength to enable longer cable runs than those permitted by the “official” cabling limits of Ethernet. Hubs and switches can be used as repeaters.

• Router—A router is used to interconnect a LAN to other networks; the name suggests the device’s similarity to an efficient travel agent, who helps a group reach its destination as quickly as possible. Routers can connect different types of networks and protocols to each other (Ethernet, token ring, TCP/IP, and so on) and are a vital part of the Internet. Router features and prices vary according to the network types and protocols supported. Modern home routers also include switches and Wi-Fi access.

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