The hub is a multi-port repeater. When the HUB is the central equipment, even if one line in the network fails, it will not affect the work of other lines. Therefore, hubs have been widely used in local area networks. Most of the time, it is used in star and tree network topology, and is connected to the host through RJ45 interface (BNC interface is also available). According to different statements, there are many kinds of hubs. According to the way of processing input signals, hubs can be divided into passive hubs, active hubs and intelligent hubs.