Hubs can be either active or passive. Passive hubs act simply as cable-connecting devices, while active hubs also serve as signal repeaters and are called "multiport repeaters". The first generation of hubs (1984) acted as LAN concentrators and repeaters, with a single internal collapsed backbone bus for connecting like LANs. The second generation accommodated multiple LAN architectures over separate ports, with rudimentary network management and configuration capabilities included as well.
Multiple hubs can be interconnected with various media, depending on bandwidth requirements and distances involved.
Hubs operate at the Physical Layer, with a hint of the Data Link Layer of the OSI Reference Model.
|Figure 10: 4-port Ethernet Hub|