Specifications

DocSTAR Level 2 Service Training Workbook Page 31
Section 2: Network Hubs, Cabling, & NICs
? This section will cover networking hardware.
Once you have decided on a network topology you must now choose the network
hardware to implement it. Some of the choices to be made are what type of hub to use or
should a switch be used instead, what type of cabling to use, and what network interface
cards to use.
Hubs and Switches
A network hub is used only in star topology based networks or hybrid star networks such
as a star bus or star ring. A hub is the central point at which all computers in a star
network connect. The hub allows one computer on the network to communicate to all the
other computers on the network. The majority of hubs in use today are ethernet hubs.
There are different types of hubs.
The first type of hub is called a Passive Hub. A passive hub is a hub that does not
require electrical power because it does not regenerate signals; it is only a connecting
point. Passive hubs are very rare since they severely limit the effective distance that
computers can be from the hub.
The second type of hub is called an Active Hub. An active hub is a hub that requires
electrical power for the purpose of regenerating signals that have been attenuated or
weakened by the distance of cable they have traveled. This increases the effective
distance a computer can be from the hub and provides better signal integrity.
Most small hubs today have a certain number of ports (usually 4-8) for computers to
connect to, via a network cable, and an uplink port. These ports are usually RJ45 ports.
RJ45 is the connector type used with twisted-pair cable. The uplink port is used to
connect a hub to another hub, thereby allowing a network to grow in size. These hubs
also have indicator LEDs on the front of them. These indicator LEDs almost always
include a power on LED, a collision detection LED, a link LED to show a positive
connection for each computer, and in the case of more advanced hubs, speed, Full
Duplex, and utilization LEDs. Some larger enterprise level hubs, stackable hubs with 12
ports or more, have a BNC connector for coaxial cable to connect stacked hubs. This
connection between main hubs is called the trunk or backbone of a network and is
usually a very high-speed connection. In some cases the backbone is a fiber-optic link,
which is the fastest network cable in use today, it is also the most expensive.
Figure 3.4 Mid-range Ethernet 16-port 10/100Mbps Active Hub