Hub (sometimes referred to as a Repeater) is a device with multiple ports which is commonly used to connect segments of a LAN. It works at the physical layer (layer 1) of the OSI model where any packet entering any port is rebroadcast on all other ports. A hub simply receives incoming Ethernet frames, regenerates the electrical signal, and broadcasts these packets out to all other devices on the network where each device on the network is responsible for determining which packets are destined for it and ignoring the others.

Unlike Switches, Hubs do not read any of the data passing through them and are not aware of their source or destination therefore, packet collisions are more frequent in networks connected using hubs than in networks connected using more sophisticated devices. Since each node in a hub-based network has to wait for an opportunity to transmit in order to avoid collisions, the latency can increase significantly as the network grows. While hubs provide an easy way to scale up and shorten the distance that the packets must travel to get from one node to another, they do not break up the actual network into discrete segments resulting in various problems in a large network.

The main reason for purchasing hubs rather than switches or routers is their price.