hubs

2.2.1 Hubs
Hubs are devices used to build networks utilizing a star topology, as shown in Figure 2.1. Hubs make it easy to add workstations to the network and to reconfigure the network at any time by simply unplugging and plugging in patch cables.



Figure 2.1 With a star topology, all devices run to a central device—a hub.
The three hub types are passive, active, and intelligent. Passive hubs allow for connections and central wiring only. Active hubs amplify the signals coming in and filter out noise. Intelligent hubs provide either switching capabilities or management features.
Switching hubs provide quick routing of signals between hub ports in order to direct data where it needs to go and reduce the bandwidth of sending the data to all locations. Switching hubs are always intelligent hubs, but intelligent hubs are not always switching hubs.

In the absence of switching, a hub sends all traffic it receives to all ports.
Hubs are occasionally known as concentrators and range in size from 4 ports to 16 ports or more. Cascading allows numerous hubs to be connected to form larger networks. Where switching is employed, it is possible for a hub to perform some of the functions of a bridge—but this is typical only if multiple networks are within a limited geographic scope.