Comptia A+, Network+ Certification Tutorial – Function Of Network Hubs
A hub is a device used to connect all of the computers on a star or ring network. A hub is nothing more than a box with a series of cable connectors in it. Hubs are available four- and five-port devices designed for home and small business networks to large rack-mounted units with up to 24 ports or more. Installing a single hub is simply a matter of connecting it to a power source and plugging in cables connected to the network interface adapters in your computers.
Hubs are associated with specific data-link layer protocols. Ethernet hubs are common, because Ethernet is a popular data-link layer protocol. Token Ring MAUs are hubs too, and other protocols, such as the Fiber Distributed Data Interface (FDDI) also use hubs.
An Ethernet hub is called a multiport repeater. A repeater is a device that amplifies a signal as it passes through it. If you have a thin Ethernet network with a cable segment longer than the prescribed maximum, you can install a repeater at some point in the segment to strengthen the signals and increase the maximum segment length. This repeater only has two BNC connectors. The hubs used on UTP Ethernet networks are repeaters as well, but they can have many RJ45 ports instead of just two BNC connectors.
When data enters the hub, the hub amplifies the signal and transmits it out through all of the other ports. This enables a star network to have a shared medium. The hub relays every packet transmitted by any computer on the network to all of the other computers, and also amplifies the signals. The maximum segment length for a UTP cable on an Ethernet network is 100 meters. A segment is defined as the distance between two communicating computers. Hubs function as a repeater, each of the cables connecting a computer to a hub port can be up to 100 meters long, allowing a segment length of up to 200 meters when one hub is inserted in the network.
