Cabling the LANs 209
Table 4-3 Comparing Ethernet Media Requirements
Media
Maximum
Segment Length
Topology Connector
10BASE2
50-ohm coaxial (thinnet) 185 m (606.94 feet) Bus British Naval Connector (BNC)
10BASE5
50-ohm coaxial (thicknet) 500 m (1640.4 feet) Bus Attachment unit interface (AUI)
10BASE-T
EIA/TIA CAT 3, 4, 5 UTP,
two pair
100 m (328 feet) Star ISO 8877 (RJ-45)
100BASE-TX
EIA/TIA CAT 5 UTP, two
pair
100 m (328 feet) Star ISO 8877 (RJ-45)
100BASE-FX
62.5/125 multimode fiber 400 m (1312.3 feet) Star Duplex media interface connector
(MIC) straight tip (ST) connector
or subscriber connector (SC)
1000BASE-CX
STP 25 m (82 feet) Star ISO 8877 (RJ-45)
1000BASE-T
EIA/TIA CAT 5 UTP, four
pair
100 m (328 feet) Star ISO 8877 (RJ-45)
1000BASE-SX
62.5/50 micro multimode
fiber

275 m (853 feet) for 62.5
micro fiber; 550 m (1804.5
feet) for 50 micro fiber
Star SC
1000BASE-LX
62.5/50 micro multimode
fiber; 9-micron single-
mode fiber
440 m (1443.6 feet) for
62.5 micro fiber; 550 m
(1804.5 feet) for 50 micro
fiber; 3 to 10 km (1.86 to
6.2 miles) on single-mode
fiber
Star SC
chpt_04.fm Page 209 Tuesday, May 27, 2003 9:01 AM
210 Chapter 4: Cable Testing and Cabling LANs and WANs
Figure 4-20 Differentiating Among Connections
Connection Media
This section briefly discusses the connection types used by physical layer implementa-
tion and an interface device, Gigabit Interface Converter (GBIC), used between the
Ethernet and fiber-optic systems. This section covers the following topics:
■ RJ-45—A connector commonly used for finishing a twisted-pair cable
■ AUI—A connector that interfaces between a computer’s NIC or router interface
and an Ethernet cable
■ GBIC—A device used as an interface between the Ethernet and fiber-optic systems
RJ-45
The RJ-45 connector and jack are the most prevalent. RJ-45 connectors are discussed
in more detail in the section, “UTP Implementation” later in the chapter.
Attachment Unit Interface

In some cases, the type of connector on a NIC does not match the type of media that it
needs to connect to. An interface exists for the AUI connector. The AUI is the 15-pin
physical connector interface between a computer’s NIC and Ethernet cable. On 10BASE5
(thicknet) Ethernet, a short cable is used to connect the AUI on the computer with a
transceiver on the main cable. In 10BASE2 (thinnet) Ethernet networks, the NIC con-
nects directly to the Ethernet coaxial cable at the back of the computer.
Gigabit Interface Converter
A Gigabit Interface Converter (GBIC) is a hot-swappable input/output device that
plugs into a Gigabit Ethernet port. A key benefit of using a GBIC is that GBICs are
interchangeable. This feature gives users the flexibility to deploy other 1000BASE-X
technology without needing to change the physical interface/module on the router or
switch.
chpt_04.fm Page 210 Tuesday, May 27, 2003 9:01 AM
Cabling the LANs 211
The fiber-optic GBIC is a transceiver that converts serial electric currents to optical sig-
nals and that also coverts optical signals to digital electric currents. Some of the optical
GBICs include the following:
■ Short wavelength (1000BASE-SX)
■ Long wavelength/long haul (1000BASE-LX/LH)
■ Extended distance (1000BASE-ZX)
Typically, the GBIC is used as an interface between the Ethernet and fiber-optic systems,
such as Fiber Channel and Gigabit Ethernet. Figure 4-21 shows a GBIC, and Figure 4-22
shows a Cisco WS-X2931 Gigabit Ethernet Module with the GBIC out.
Figure 4-21 Gigabit Interface Converter (GBIC)
Figure 4-22 Cisco WS-X2931 Gigabit Ethernet Module with GBIC Out
chpt_04.fm Page 211 Tuesday, May 27, 2003 9:01 AM
212 Chapter 4: Cable Testing and Cabling LANs and WANs
UTP Implementation
If you look at the RJ-45 transparent end connector, you can see eight colored wires.
These wires are twisted into four pairs. Four of the wires (two pairs) carry the positive,

or true, voltage and are considered “tip” (T1 through T4); the other four wires carry
the inverse, or false, voltage grounded and are called “ring” (R1 through R4). Tip and
ring are terms that originated in the early days of the telephone. Today, these terms
refer to the positive and the negative wire in a pair. The wires in the first pair in a cable
or a connector are designated as T1 and R1, the second pair is T2 and R2, and so on.
The RJ-45 plug is the male component, crimped at the end of the cable. As you look
at the male connector from the front, with the clip facing down, the pin locations are
numbered from 8 on the left down to 1 on the right, as shown in Figure 4-23. The
jack, shown in Figure 4-24, is the female component in a network device, wall or cubi-
cle partition outlet, or patch panel. As you look at the device port, the corresponding
female pin locations are 1 on the left up to 8 on the right.
Figure 4-23 Pin Locations on the RJ-45 Connector
For electricity to run between the connector and the jack, the order of the wires must fol-
low EIA/TIA-568-A and EIA/TIA-568-B standards, as shown previously in Figure 4-16.
In addition to identifying the correct EIA/TIA category of cable to use for a connecting
device (which depends on what standard is being used by the jack on the network
device), you need to determine which of the following to use:
■ A straight-through cable—A cable that maintains the pin connection all the way
through the cable. Thus, the wire connected to pin 1 is the same on both ends of
the cable.
■ A crossover cable—A cable that crosses the critical pair to properly align, trans-
mit, and receive signals on the device with line connections.
chpt_04.fm Page 212 Tuesday, May 27, 2003 9:01 AM
Cabling the LANs 213
Figure 4-24 RJ-45 Jack and Wire Order
If the two RJ-45 ends of a cable are held side by side in the same orientation, the col-
ored wires (or strips or pins) are seen at each connector end. If the order of the colored
wires is the same at each end, the cable is straight-through. Figure 4-25 illustrates that
the RJ-45 connectors on both ends show all the wires in the same order.
Figure 4-25 UTP Implementation: Straight-Through Cable

chpt_04.fm Page 213 Tuesday, May 27, 2003 9:01 AM
214 Chapter 4: Cable Testing and Cabling LANs and WANs
Specified for Ethernet, in a CAT 5 UTP cable, only wires 1, 2, 3, and 6 are used for
transmit (TD) and receive (RD) signals. The other four wires are not used. As shown
on the left of Figure 4-25, in a straight-through cable, the RJ-45 pins 1, 2, 3, and 6 at
one end are connected to pins 1, 2, 3, and 6 at the other end of the connection. Gigabit
Ethernet, however, uses all eight wires.
You can use a straight-through cable to connect devices such as PCs or routers to other
devices used as hubs or switches. As Figure 4-26 shows, you should use straight-through
when only one port is designated with an x.
Figure 4-26 Interconnecting Devices Using Straight-Through Cable
With crossover cable, the RJ-45 connectors on both ends show that some of the wires
on one side of the cable are crossed to a different pin on the other side of the cable.
Specifically for Ethernet, pin 1 at one RJ-45 end should connect to pin 3 at the other
end. Pin 2 at one end should connect to pin 6 at the other end, as shown in Figure 4-27.
Figure 4-27 UTP Implementation—Crossover
chpt_04.fm Page 214 Tuesday, May 27, 2003 9:01 AM
Cabling the LANs 215
You can use a crossover cable to connect similar devices, switch to switch or switch to
hub. Figure 4-28 shows that you use a crossover cable when both ports are designated
with an x or when neither port is designated with an x.
Figure 4-28 Interconnecting Devices Using Crossover Cable
The following are the guidelines for the type of cable to use when interconnecting net-
working devices.
Use straight-through cables for the following cabling:
■ Switch to router
■ Switch to PC or server
■ Hub to PC or server
Use crossover cables for the following cabling:
■ Switch to switch

■ Switch to hub
■ Hub to hub
■ Router to router
■ PC to PC
■ Router to PC
Lab Activity Punch-Down Jacks
In this lab, you learn to wire an RJ-45 data jack for installation in a wall plate
using a punch-down tool.
chpt_04.fm Page 215 Tuesday, May 27, 2003 9:01 AM
216 Chapter 4: Cable Testing and Cabling LANs and WANs
LAN Connection Devices
Many types of devices are connected to make up a LAN. These are called the LAN
hardware components. This section discusses some of the common hardware compo-
nents that are used in a LAN environment. LAN devices can include repeaters, hubs,
bridges, switches, and routers with switches being the most prevalent device in modern
LANs.
Repeaters
As mentioned in the section, “LAN Physical Layer” and shown in Figure 4-19, many
types of media exist, and each one has advantages and disadvantages. One of the dis-
advantages of the CAT 5 UTP cable that is primarily used is cable length. The maximum
length for UTP cable in a network is 100 meters (approximately 333 feet). If you have
to expand the network beyond that limit, you need to add a repeater. In most Ethernet
networks this repeater normally takes the form of hub, which is a multiport repeater, or
a newer technology switch.
The term repeater comes from the early days of visual communication when a person
situated on a hill would repeat the signal that was just received from the person on the
previous hill to communicate the signal to the person on the next hill. Telegraph, tele-
phone, microwave, and optical communications all use repeaters to strengthen their
signals over long distances.
The purpose of a repeater, shown in Figures 4-29 and 4-30, is to regenerate and retime

network signals at the bit level to allow them to travel a longer distance on the media.
Repeaters are commonly used if too many network nodes exist or the number of cables
is insufficient. The Four Repeater Rule for 10 Mbps bus-based Ethernet, also know as
the 5-4-3 Rule, is used as a standard when extending LAN segments. This rule states that
no more than five network segments can be connected end-to-end using four repeaters,
but only three segments can have hosts (computers) on them. Although the 5-4-3 rule
is important when applied to bus-based networks, it does not have much validity with
switches and extended star topologies.
chpt_04.fm Page 216 Tuesday, May 27, 2003 9:01 AM
LAN Connection Devices 217
Figure 4-29 Repeaters
Figure 4-30 Repeaters Connect Two End Nodes
Hubs
Hubs are actually multiport repeaters. In many cases, the difference between the two
devices is the number of ports that each provides. While a typical repeater has just 2
ports, a hub generally has from 4 to 24 ports, as shown in Figure 4-31. Additionally,
hubs are most commonly used in Ethernet 10BASE-T or 100BASE-T networks,
although other network architectures use them as well.
chpt_04.fm Page 217 Tuesday, May 27, 2003 9:01 AM
218 Chapter 4: Cable Testing and Cabling LANs and WANs
Figure 4-31 Eight-Port Hub
Using a hub changes the network topology from a linear bus, where each device plugs
directly into the wire, to a star. With hubs, data arriving over the cables to a hub port
is electrically repeated on all the other ports connected to the same network segment,
except for the port on which the data was sent.
Hubs come in two basic types:
■ Active—An active hub must be plugged into an electrical outlet because it needs
power to amplify the incoming signal before passing it out to the other ports.
■ Intelligent—An intelligent hub are sometimes called smart hubs. These devices
basically function as active hubs, but also include a microprocessor chip and

diagnostic capabilities. They are more expensive than active hubs, but are useful
in troubleshooting situations.
All devices that are attached to a hub hear all traffic. Therefore, hubs maintain a single
collision domain. A collision is a situation where two end stations send data over the
network wire at the same time.
Sometimes, hubs are called concentrators because they serve as a central connection
point for an Ethernet LAN.
Bridges
At times, you need to break up a large LAN into smaller, more easily managed seg-
ments. This strategy decreases the amount of traffic on a single LAN and can extend
Lab Activity Hubs Purchase
In this lab, you are introduced to the variety and prices of network compo-
nents out in the market. This lab looks specifically at Ethernet hubs and NICs.
chpt_04.fm Page 218 Tuesday, May 27, 2003 9:01 AM