An
Ethernet hub,
active hub,
network hub,
repeater hub,
multiport repeater, or simply
hub is a
network hardware device for connecting multiple
Ethernet devices together and making them act as a single
network segment. It has multiple
input/output (I/O) ports, in which a
signal introduced at the input of any
port appears at the output of every port except the original incoming. A hub works at the
physical layer (layer 1) of the
OSI model. Repeater hubs also participate in collision detection, forwarding a
jam signal to all ports if it detects a
collision. In addition to standard
8P8C ("RJ45") ports, some hubs may also come with a
BNC or
Attachment Unit Interface (AUI) connector to allow connection to legacy
10BASE2 or
10BASE5 network segments.