Ethernet is a hub-based network architecture, meaning that all the data that flows through an Ethernet network must flow through a hub of one type or another.
The exception to this rule is using an Ethernet crossover cable to connect two devices. This special cable acts as a very basic hub, so there is no need to use a specific hub device.
→ To learn more about Ethernet, see “Ethernet,” p. 625.
The basic function of an Ethernet hub is to enable data to flow through an Ethernet network. There are three basic types of Ethernet hubs.
Passive or “Dumb” Hubs These hubs don't do anything but allow data to be passed back and forth between the devices to which they are connected. ...