Segments are created on a network to improve network performance or security.
Installing a bridge, router, or switch (see the following section for information on these
networking devices) at strategic locations on a network creates network segments.Networking Devices
A variety of networking devices is used on networks to improve the network’s perfor-
mance, to extend the effective range of its media, or to overcome hardware limitations.
The following sections cover the most commonly used networking devices.Repeaters
A repeater is the simplest of the networking devices. A repeater is an electronic echo ma-
chine that has no other function. It simply retransmits whatever it receives on one port
out the other port, reenergizing the signal’s strength. Repeaters are used to extend the
maximum segment length of the network cabling and protect against attenuation. By
regenerating the signal before the maximum segment length of the cable media is
reached, the reenergized signal is able to reach its destination.Hubs
As illustrated in Figure 20-8, a hub is a networking device used to connect PCs, workstations,
and peripheral devices to the network. Each workstation or device is plugged into one of the
hub’s ports along with a connection to the network’s backbone. In general, a hub receives a
signal from one port and passes it on to all of its other ports and to whatever is attached to
these ports. For example, if an 8-port hub receives a signal on port 4, it immediately passes
the signal to ports 1, 2, 3, 5, 6, 7, and 8.
Hubs are commonly used on Ethernet twisted pair networks, especially 10BaseT and
100BaseT configurations. A typical hub is configured with 8, 16, or 24 ports. There are
four types of hubs used on networks: Active hub Acts like a repeater to amplify the signal being passed on and
serves as a traffic cop to avoid signal collisions.
Passive hub Passes along the signal without amplifying it.
Hybrid hub Can mix media types (thin coax, thick coax, and twisted pair)
and serve as an interconnect for other hubs. Fiber optic cable requires a
transceiver, so hubs do not typically support it.
Smart (intelligent) hub An active hub with a bigger brain. Smart hubs
include some administrative interface, often SNMP (Simple Network
Management Protocol) support or the ability to segment the ports into
different logical networks.Chapter 20: Networks and Communications^521