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Introduction to Hubs
Part 1 - Introduction and Key Features
An Article by your Guide Bradley Mitchell

Until the early 2000s, Ethernet hubs were an extremely attractive home networking option due to their simplicity and low cost. Nowadays, broadband routers are the popular choice for Ethernet connections in homes. Hubs still serve a useful purpose though. Do you own a hub, or are you considering purchasing one? This article explains the purpose of hubs and some of the technology behind them... (see below)
 More of this Feature
• Which Hub is Right for You?
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"Hubs broadcast and repeat what they hear; switches provide dedicated bandwidth with very little window for collisions to take place due to their point-to-point nature."
 Related Resources
• Best Dual-Speed Ethernet Hubs for Home

• Internetworking Directory
General Characteristics of Hubs

A hub is a small rectangular box, often made of plastic, that receives its power from an ordinary wall outlet. A hub joins multiple computers (or other network devices) together to form a single network segment. On this network segment, all computers can communicate directly with each other. Ethernet hubs are by far the most common type, but hubs for other types of networks such as USB also exist.

A hub includes a series of ports that each accept a network cable. Small hubs network four computers. They contain four or sometimes five ports, the fifth port being reserved for "uplink" connections to another hub or similar device. Larger hubs contain eight, 12, 16, and even 24 ports.

Key Features of Hubs

Hubs classify as Layer 1 devices in the OSI model. At the physical layer, hubs can support little in the way of sophisticated networking. Hubs do not read any of the data passing through them and are not aware of their source or destination. Essentially, a hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts these packets out to all devices on the network - including the one that originally sent the packet!

Technically speaking, three different types of hubs exist:

  • passive
  • active
  • intelligent

Passive hubs do not amplify the electrical signal of incoming packets before broadcasting them out to the network. Active hubs, on the other hand, do perform this amplification, as does a different type of dedicated network device called a repeater. Some people use the terms concentrator when referring to a passive hub and multiport repeater when referring to an active hub.

Intelligent hubs add extra features to an active hub that are of particular importance to businesses. An intelligent hub typically is stackable (built in such a way that multiple units can be placed one on top of the other to conserve space). It also typically includes remote management capabilities via SNMP and virtual LAN (VLAN) support.

Hubs remain a very popular device for small networks because of their low cost. A good five-port Ethernet hub can be purchased for less than $30 USD. USB hubs cost only a bit more.

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