10.1 Network Cabling

A network cable carries data from one device to another.

Example

PC ===== Ethernet Cable ===== Switch

Different cable types are designed for different:

• Speeds
• Distances
• Environments
• Interference levels
• Connectors

The main wired media categories you will study are:

• Copper
• Fiber
• Coaxial

This chapter focuses mainly on copper twisted-pair Ethernet cabling.

10.2 Twisted-Pair Cable

Twisted-pair cable contains copper wires twisted together in pairs.

A typical Ethernet cable contains:

4 twisted pairs = 8 wires

Conceptually

Pair 1: twisted wires
Pair 2: twisted wires
Pair 3: twisted wires
Pair 4: twisted wires

Why twist the wires?

To help reduce electromagnetic interference and crosstalk.

10.3 Unshielded Twisted Pair — UTP

UTP stands for:

Unshielded Twisted Pair

It is one of the most common Ethernet cable types.

UTP uses twisted pairs but does not add extensive metallic shielding around them.

Example

PC ---- UTP Cable ---- Switch

Advantages

UTP is generally:

• Inexpensive
• Lightweight
• Flexible
• Easy to install
• Commonly available

Disadvantage

It can be more susceptible to electromagnetic interference than shielded cabling.

10.4 Shielded Twisted Pair — STP

STP stands for:

Shielded Twisted Pair

STP adds shielding to help protect against electromagnetic interference.

Example environments

• Industrial facilities
• Areas near motors
• Areas near electrical equipment
• Locations with significant interference

UTP vs STP

10.5 Category 5 — Cat 5

Cat 5 is an older twisted-pair cable category.

It historically supported speeds such as:

100 Mbps Ethernet

It is now considered outdated for most new installations.

You are more likely to encounter:

• Cat 5e
• Cat 6
• Cat 6a

10.6 Category 5e — Cat 5e

Cat 5e means:

Category 5 Enhanced

It commonly supports:

1 Gbps up to 100 meters

under normal Ethernet conditions.

Example

PC ===== Cat 5e ===== Switch
          1 Gbps

Cat 5e is still common in many homes and offices.

10.7 Category 6 — Cat 6

Cat 6 provides better performance than Cat 5e.

It can commonly support:

1 Gbps up to 100 meters

and can support:

10 Gbps over shorter distances

often around 55 meters, depending on environment and installation conditions.

Why?

Cat 6 has improved specifications for:

• Crosstalk
• Signal quality
• Frequency

10.8 Category 6a — Cat 6a

Cat 6a means:

Category 6 Augmented

It is designed to support:

10 Gbps up to 100 meters

This makes it useful for higher-speed enterprise installations.

Comparison

Cat 5e
1 Gbps / 100 m

Cat 6
1 Gbps / 100 m
10 Gbps / shorter distance

Cat 6a
10 Gbps / 100 m

10.9 Category 7 — Cat 7 Concepts

Cat 7 is a shielded cabling standard encountered in some environments.

However, for mainstream Ethernet installations, Cat 6a and Cat 8 are more directly relevant to common standards and Networking discussions.

For the exam, focus primarily on:

• Cat 5e
• Cat 6
• Cat 6a
• Cat 8

10.10 Category 8 — Cat 8

Cat 8 is designed for very high-speed short-distance Ethernet.

It can support:

• 25 Gbps
• 40 Gbps

over relatively short distances, commonly around:

30 meters

It is often associated with:

• Data centers
• Switch-to-server connections
• Short high-speed copper runs

Important comparison

Cat 5e
Longer general office use

Cat 6a
10 Gbps up to 100 m

Cat 8
Very high speed, short distance

10.11 RJ45

The common modular connector used for Ethernet twisted-pair cabling is often called:

RJ45

Example

[Ethernet Plug]

||||||||

8 contacts

Ethernet twisted-pair cabling uses:

8 positions / 8 contacts

You may also see this described technically as an:

8P8C modular connector

10.12 T568A

T568A is one standard for arranging the wires inside an Ethernet connector.

Pin order

1  White/Green
2  Green
3  White/Orange
4  Blue
5  White/Blue
6  Orange
7  White/Brown
8  Brown

You do not need to physically build cables for every Networking question, but recognizing T568A and T568B is useful.

10.13 T568B

T568B is another common wiring standard.

Pin order

1  White/Orange
2  Orange
3  White/Green
4  Blue
5  White/Blue
6  Green
7  White/Brown
8  Brown

Difference

The orange and green pairs are swapped compared with T568A.

10.14 Straight-Through Cable

A straight-through cable uses the same wiring standard on both ends.

Example

End A = T568B
End B = T568B

or:

End A = T568A
End B = T568A

Historically, straight-through cables were commonly used between different device types.

Example

PC -------- Switch

Modern Ethernet devices with Auto-MDI/MDIX make this distinction much less important in everyday use.

10.15 Crossover Cable

A crossover cable uses different wiring standards at the two ends.

Example

End A = T568A
End B = T568B

Historically, crossover cables were commonly used between similar Ethernet devices.

Examples

PC ------ PC

Switch ------ Switch

Again, modern Auto-MDI/MDIX usually removes the need to manually choose crossover cables.

10.16 Auto-MDI/MDIX

Auto-MDI/MDIX allows Ethernet devices to automatically detect which transmit and receive wire pairs should be used.

This means modern devices can often work with either:

• Straight-through cable
• Crossover cable

Example

Switch A -------- Switch B

Even if the cable is straight-through, Auto-MDI/MDIX can automatically adjust.

10.17 Plenum Cable

Plenum-rated cable is designed for installation in plenum air-handling spaces.

A plenum space may be above a suspended ceiling where air circulates for heating or cooling.

Example

Ceiling
-------------------
Plenum Air Space
Network Cable
-------------------
Office

Why special cable?

When burned, ordinary cable jackets may release more smoke and toxic gases.

Plenum-rated cable is designed to meet stricter fire and smoke requirements.

10.18 Riser Cable

Riser-rated cable is designed for vertical cable runs between floors.

Example

Floor 3
   |
   | cable
   |
Floor 2
   |
   | cable
   |
Floor 1

The vertical shaft is sometimes called a riser.

Plenum vs riser

Plenum
= Air-handling space

Riser
= Vertical floor-to-floor run

Plenum cable generally has stricter fire/smoke requirements.

10.19 Patch Cable

A patch cable is a short network cable used to connect devices.

Examples

• PC → Wall Jack
• Patch Panel → Switch
• Router → Switch

A patch cable is usually flexible and designed for short connections.

10.20 Patch Panels

A patch panel provides an organized termination point for many network cables.

Example

Office Cables
      |
      ↓
Patch Panel
      |
Short Patch Cables
      |
      ↓
Switch

The permanent cable from an office wall outlet often terminates at the patch panel.

Then a short patch cable connects:

Patch Panel → Switch

Benefits

• Organization
• Easier troubleshooting
• Easier changes
• Cleaner cabling

10.21 Punch-Down Blocks

A punch-down block or punch-down connection is used to terminate individual wires.

A technician uses a:

Punch-down tool

to seat wires into slots.

Example

Cable
  |
Individual wires
  |
Patch panel terminals

The punch-down tool pushes each wire firmly into its termination point.

Common locations

• Patch panels
• Keystone jacks
• Telecommunications blocks

10.22 Cable Distance Limitations

For many twisted-pair Ethernet standards, the maximum channel length is:

100 meters

A common structured-cabling design is:

90 m permanent horizontal cable

+

10 m patch cables

=

100 m total channel

Why is distance important?

As distance increases:

• Signal weakens
• Errors may increase
• Communication may fail

If you need much longer distances, fiber is often preferred.

10.23 Electromagnetic Interference — EMI

EMI stands for:

Electromagnetic Interference

Electrical equipment can create electromagnetic fields that interfere with copper network signals.

Common EMI sources

• Motors
• Fluorescent lights
• Power cables
• Generators
• Industrial equipment
• Transformers

Example

Power Cable   ==========

Network Cable ==========

Too close together

→ possible interference

Ways to reduce EMI

• Keep data cables away from power cables
• Cross electrical cables at approximately 90 degrees when necessary
• Use shielded cabling
• Use fiber where interference is severe

10.24 Crosstalk

Crosstalk happens when a signal from one wire pair interferes with another pair.

Imagine

Pair A: DATA DATA DATA
        ↓ unwanted interference
Pair B: DATA DATA DATA

Twisting the wires helps reduce this problem.

Common terms include:

• NEXT
• FEXT

NEXT

Near-End Crosstalk

Interference measured near the transmitting end.

FEXT

Far-End Crosstalk

Interference measured at the far end.

10.25 Attenuation

Attenuation means:

Loss of signal strength over distance

Imagine shouting to someone.

At 2 meters:

Very clear.

At 200 meters:

Much harder to hear.

Network signals behave similarly.

Example

Strong signal

██████████

↓ distance

Weak signal

███

Too much attenuation can cause:

• Errors
• Lost frames
• Unstable connections
• No connection

Causes

• Cable too long
• Poor cable quality
• Damaged cable
• Bad connectors

10.26 Copper Cable Troubleshooting

Now combine the concepts.

Common copper problems include:

• Open
• Short
• Incorrect pinout
• Split pair
• Crosstalk
• EMI
• Attenuation
• Damaged connector
• Excessive cable length
• Wrong cable category

Open Circuit

An open means a conductor is broken somewhere.

Example

Wire ----------------X---------------- Wire

The electrical path is incomplete.

Possible symptom:

No connectivity

A cable tester can detect this.

Short Circuit

A short occurs when two conductors make unintended contact.

Example

Wire A ------\
             X
Wire B ------/

Possible symptoms:

• No connection
• Errors
• Intermittent connectivity

Incorrect Pinout

The wires may be terminated in the wrong positions.

Example

Expected:

1 → White/Orange

2 → Orange

But installed:

1 → Blue

2 → Brown

The cable may not work properly.

Split Pair

A split pair can happen when the correct pin numbers appear connected, but wires from the wrong twisted pairs are used.

This is tricky because a basic continuity test may look acceptable, but Ethernet performance may be poor.

Symptoms can include:

• Errors
• Slow speed
• Unstable gigabit connection

Damaged Connector

Problems can occur if:

• RJ45 tab breaks
• Contacts are bent
• Cable is poorly crimped
• Wires are not seated fully

Example

PC ---- damaged RJ45 ---- Switch

Cable Too Long

If a twisted-pair Ethernet cable exceeds its supported distance, the signal can become too weak.

Example

PC =============================== Switch

               140 meters

If the Ethernet standard expects 100 meters maximum, this can cause errors.

Wrong Cable Category

Suppose a network is upgraded to 10 Gbps, but old cabling cannot reliably support that speed.

Possible result:

• Link negotiates lower
• Errors
• Unstable performance
• No 10 Gbps connection

Copper Ethernet Category Comparison

Chapter 10 Practice Questions