An ethernet hub is an electronic device that runs a computer network. It is a simple device and is easy to configure. A hub acts like a repeater: all data that arrives to one port is sent to all other ports (without looking at IP address for the data's destination). That means that all devices in this network will get all data. So, this slows the network. A hub is very simple device and does not operate Ethernet traffic. In contrast, a switch hub has a lower latency. Many hubs have LED signal lamps to show the state of the hub (which ports are connected and if the hub working). A "collision" happens when two or more devices on the same network try to send packets at the same time. When collisions happen all of the devices have to go through a routine to resolve the conflict. The process is set in the Ethernet Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.
Some hubs may also come with a BNC and/or Attachment Unit Interface (AUI) connector to allow connection to legacy 10BASE2 or 10BASE5 network segments.
There are three kinds of hubs:
- Hub - This one described here. The hub does not look at individual packets and copies them to all ports, used as connection between LAN Segments.
- Passive hub (intelligent hub) - The device monitors traffic going through the hub and all ports can be configured, also are called manageable hubs.
- Switching hub - reads the destination address of each packet and then forwards the packet to the just correct port.
Hubs can be used for:
- inserting a protocol analyzer into a network connection, a hub is an alternative to a network tap or port mirroring.
- preventing a "loop" by accidentally connecting two ports together, which might be big problem when switches are used.
- working on Physical Layer of OSI.
Historically, the main reason for purchasing hubs rather than switches was their price. Today few hubs are produced, because they are not an effective solution for building networks.