Hub

A hub is a simple network component that forwards incoming data packets to all connected ports. It operates at the physical layer of the OSI model and evaluates neither MAC addresses nor destination addresses. All devices attached to a hub therefore share a single collision domain, which divides the available bandwidth and causes collisions when several devices transmit simultaneously. Operation is limited to half duplex mode. For these reasons, hubs have been fully replaced by switches in corporate networks, as switches forward packets specifically to the destination port and support full duplex. Today, hubs are only found in legacy installations or occasionally in network analysis, when all traffic within a segment needs to be captured. For productive environments, switches are the standard.