CompTIA Network+ N10-008 Study Guide

Course: Networking Fundamentals and Physical Networks Source basis: Coursera course videos and readings reviewed on 2026-06-19 Purpose: Exam-focused study notes for the course modules. This is an original study guide, not a transcript.

How To Use This Guide

Read one module at a time.
Memorize the "must know" lists first.
Use the checklists to identify weak spots.
Take the practice question set after reviewing all modules.
Review explanations for missed questions, then return to the related section.

High-Yield Memory Anchors

OSI layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.
Layer 1 moves bits. Layer 2 uses MAC addresses and frames. Layer 3 uses IP addresses and packets. Layer 4 uses ports and segments/datagrams.
MAC addresses are 48-bit physical addresses commonly written as 12 hexadecimal characters.
IPv4 addresses are 32-bit logical addresses commonly written in dotted decimal.
Ethernet frames are the Layer 2 data unit used on Ethernet LANs.
A switch forwards frames based on MAC addresses. A hub repeats bits to all ports.
Star topology is the most common physical LAN topology today.
UTP is common for Ethernet. Fiber is preferred for long distance, high bandwidth, and EMI resistance.
T568A and T568B are wiring standards. Use the same standard on both ends for a straight-through cable.
Full duplex avoids collisions. Half duplex requires collision handling.
Structured cabling organizes horizontal cabling, patch panels, wall outlets, equipment rooms, and work areas.
Cable troubleshooting starts with link lights, physical inspection, known-good cables, and the right tester.

Module 1: Network Models

Big Picture

Network models help explain how data moves through a network. They divide a complex communication process into layers, which makes design, troubleshooting, and security easier. The course emphasizes the OSI seven-layer model as a way to reason from the physical cable or radio signal up to the user-facing application.

OSI Model

The OSI model has seven layers:

Physical
Data Link
Network
Transport
Session
Presentation
Application

Layer 1: Physical

The Physical layer defines how bits move from one device to another. It includes cabling, connectors, radio frequencies, signaling, voltages, pinouts, and the physical properties of a link.

Know these examples:

Copper cabling
Fiber optic cabling
Wireless radio frequencies
Connectors such as RJ-45
Signaling and physical media standards
Link lights and physical connectivity

Layer 1 problems usually look like no link, damaged cable, bad connector, wrong cable type, excessive distance, broken fiber, EMI, or failed hardware port.

Layer 2: Data Link

The Data Link layer handles local network delivery. Ethernet operates here. Devices use MAC addresses to determine whether a frame is meant for them.

Important Layer 2 concepts:

Ethernet frames
Source and destination MAC addresses
Switch forwarding
Local delivery on a LAN
Frame check sequence
Broadcast and unicast traffic

Layer 2 is about getting frames to the right local system. A device compares the destination MAC address in a frame to its own MAC address. If it matches, the frame is accepted. If not, it is ignored unless the traffic is broadcast or the NIC is in a special mode.

Layer 3: Network

The Network layer uses logical addressing. IP is the core Layer 3 protocol for Network+.

Important Layer 3 concepts:

IPv4 and IPv6 addressing
Source and destination IP addresses
Routing between networks
Packets
Logical addressing

MAC addresses are useful on the local LAN, but IP addressing is needed for communication across routed networks such as the internet.

Layer 4: Transport

The Transport layer handles segmentation, reassembly, and ports. Large application data must be broken into pieces that fit inside frames. On the receiving side, those pieces must be reassembled.

Know these Layer 4 ideas:

TCP and UDP
Port numbers
Segmentation and reassembly
Sessions between applications
Reliability when using TCP
Lower overhead when using UDP

The course highlights that Ethernet has a practical payload limit, so large files must be chopped into smaller chunks before transmission.

Layers 5-7: Upper Layers

The upper layers deal with conversations, formatting, encryption, and user-facing network services.

Session: Establishes, manages, and ends communication sessions.
Presentation: Handles data formatting, compression, and encryption/decryption.
Application: Provides network services to user applications, such as web, email, file transfer, and name resolution services.

For Network+, you should know the layers, what each one does, and how to map common protocols/devices/problems to the right layer.

Encapsulation and Decapsulation

When data is sent, each layer adds its own information. This is encapsulation. When data is received, each layer removes and processes its own information. This is decapsulation.

Common data units:

Bits at Layer 1
Frames at Layer 2
Packets at Layer 3
Segments or datagrams at Layer 4
Data at upper layers

Ethernet Frame Basics

An Ethernet frame carries data across a local Ethernet network.

Key frame fields to understand:

Preamble: Signals that a frame is arriving.
Destination MAC address: Identifies the intended receiver on the local link.
Source MAC address: Identifies the sender on the local link.
Type/length field: Identifies the payload type or length.
Payload: The carried data, often an IP packet.
Frame check sequence: Helps detect transmission errors.

The frame check sequence does not fix errors by itself. It lets the receiving device detect that a frame was damaged.

MAC Addresses

A MAC address is a 48-bit hardware address used at Layer 2. It is commonly written as six pairs of hexadecimal digits.

Important facts:

48 bits total.
Usually burned into the network interface.
Used for local LAN delivery.
Switches learn source MAC addresses and build MAC address tables.
The first portion identifies the vendor, called the OUI.
The rest identifies the specific interface.

Do not confuse MAC and IP addresses. MAC addresses are local physical/link-layer identifiers. IP addresses are logical network-layer identifiers used across routed networks.

Broadcast vs Unicast

Unicast traffic is one-to-one. A frame is sent to one destination MAC address.

Broadcast traffic is one-to-all within the local broadcast domain. Ethernet broadcast uses destination MAC address FF:FF:FF:FF:FF:FF.

Exam points:

Switches forward broadcasts out all ports in the same VLAN except the incoming port.
Routers do not normally forward Layer 2 broadcasts.
Too much broadcast traffic can hurt performance.
ARP is a common broadcast-driven process in IPv4 networks.

IP Addressing Introduction

IPv4 addresses are 32-bit logical addresses. They are written in dotted decimal, such as 192.168.1.10.

IP addresses identify:

The network portion.
The host portion.

Routers use the network portion to move packets between networks. Hosts use a subnet mask or prefix length to determine whether a destination is local or remote.

Packets and Ports

IP packets carry Layer 4 data. TCP and UDP use port numbers so traffic reaches the correct application or service.

Examples to know:

HTTP: TCP 80
HTTPS: TCP 443
DNS: UDP/TCP 53
SSH: TCP 22
FTP control: TCP 21
SMTP: TCP 25
DHCP server/client: UDP 67/68

Ports let one host run many network services at the same IP address.

Module 1 Must Know

OSI layer order and function.
Difference between frames, packets, and segments.
Difference between MAC and IP addresses.
How encapsulation works.
What Ethernet frame fields do.
What broadcast and unicast mean.
Why ports are needed.

Module 2: Cabling and Topology

Big Picture

Physical network design includes topology, cabling type, connector type, distance, bandwidth, safety ratings, and installation environment. A good design must work electrically or optically, be maintainable, and meet building/fire requirements.

Network Topologies

Bus

All devices share one backbone cable. Older coaxial Ethernet used bus designs.

Pros:

Simple in small old networks.
Less cable than some designs.

Cons:

A break can affect many devices.
Harder to troubleshoot.
Shared media limits performance.
Rare in modern Ethernet LANs.

Ring

Each device connects to two neighbors, forming a loop.

Pros:

Predictable traffic flow in classic ring systems.

Cons:

Failure can disrupt the ring unless redundancy exists.
Not common in modern office Ethernet LANs.

Star

Each device connects to a central device, usually a switch.

Pros:

Common modern LAN design.
Easy to add/remove devices.
Easier troubleshooting.
A single cable failure usually affects one endpoint.

Cons:

Central switch is a critical dependency.

Mesh

Devices have multiple interconnections.

Pros:

High redundancy.
Useful for backbones, WANs, wireless mesh, and critical links.

Cons:

More expensive.
More complex to manage.

Hybrid

Most real networks combine topology ideas. A LAN may be physically star-shaped, while switches may be connected in a partial mesh or hierarchical design.

Coaxial Cabling

Coax uses a central conductor, insulation, shielding, and an outer jacket. It was common in older Ethernet and is still seen in cable internet and video distribution.

Know:

RG-6 is common for cable TV/cable internet.
RG-59 is older/thinner and common in some video/security installations.
BNC connectors are associated with older coax Ethernet.
F-type connectors are common with cable TV/cable modem use.

Exam value:

Coax is shielded and can be durable.
It is not the normal choice for modern switched Ethernet endpoints.

Twisted Pair Cabling

Twisted pair is the most common copper media for Ethernet LANs.

Types:

UTP: Unshielded twisted pair. Common, inexpensive, flexible.
STP/FTP variants: Shielded or foil-shielded designs for noisier environments.

Why twist pairs?

Twisting helps reduce electromagnetic interference and crosstalk.
Different twist rates reduce interference between pairs.

Common categories:

Cat 5e: Common for 1 Gbps up to 100 meters.
Cat 6: Supports 1 Gbps to 100 meters and 10 Gbps at shorter distances.
Cat 6a: Better support for 10 Gbps up to 100 meters.

Connector:

8P8C modular connector, commonly called RJ-45.

Important maximum:

Copper Ethernet horizontal runs are commonly limited to 100 meters total channel length.

Fiber Optic Cabling

Fiber uses light instead of electrical signals.

Advantages:

Longer distances.
Higher bandwidth potential.
Immune to EMI/RFI.
Harder to tap casually than copper.
Useful between buildings or in electrically noisy environments.

Types:

Multimode fiber: Larger core, shorter distances, often used inside buildings and data centers.
Single-mode fiber: Smaller core, longer distances, often used for campus, metro, and carrier links.

Common connectors:

LC: Small form factor, very common with modern transceivers.
SC: Square push-pull connector.
ST: Older bayonet-style connector.

Fiber exam cautions:

Match fiber type, transceiver type, wavelength, and connector.
Keep connectors clean.
Observe bend radius.
Do not look into fiber ends.

Fire Ratings

Cable jacket ratings matter because cables can spread smoke or flame through a building.

Common ratings:

Plenum-rated cable: Used in plenum air-handling spaces. More expensive, produces less toxic smoke.
Riser-rated cable: Used for vertical runs between floors.
PVC/general-purpose cable: Common patch cable jacket, not for plenum spaces.

Exam clue:

If the question mentions air-handling space, HVAC return, drop ceiling used for airflow, or plenum, choose plenum-rated cable.

Module 2 Must Know

Star topology is common for modern Ethernet LANs.
Bus and coax are older Ethernet concepts but still exam-relevant.
UTP is common for LAN drops.
Fiber is best for long distance and EMI-heavy environments.
Plenum/riser ratings are safety requirements, not performance ratings.
Cable category affects supported speed and distance.

Module 3: Ethernet Basics

Big Picture

Ethernet defines how devices communicate on wired LANs. Modern Ethernet uses switches, MAC addressing, frames, and structured cabling. Understanding Ethernet means understanding frames, termination, switching, and how devices connect.

What Ethernet Is

Ethernet is a family of LAN technologies defined by IEEE 802.3. It includes physical media standards and frame behavior.

Core points:

Ethernet uses frames at Layer 2.
Ethernet uses MAC addresses for local delivery.
Modern Ethernet usually uses switches.
Ethernet standards define speed, media, connector expectations, and distance.

Ethernet Frames

Important frame components:

Preamble and start frame delimiter: Synchronization and frame start.
Destination MAC address: Receiver.
Source MAC address: Sender.
Type/length: Payload type or size information.
Payload: Often an IP packet.
FCS: Error detection.

Minimum and maximum sizes are exam-relevant. Standard Ethernet payload is commonly up to 1500 bytes. Jumbo frames exceed the standard MTU and must be supported consistently by the devices in the path.

Terminating Twisted Pair

Twisted pair cables must be terminated correctly so each wire lands on the correct pin.

Standards:

T568A
T568B

Straight-through cable:

Same standard on both ends.
Used for typical endpoint-to-switch connections.

Crossover cable:

T568A on one end and T568B on the other.
Historically used for like-device connections, such as switch-to-switch or PC-to-PC.
Less necessary today because many ports support Auto-MDIX.

Important installation habits:

Keep pairs twisted as close as practical to the termination.
Avoid excessive untwisting.
Do not exceed bend radius.
Use the right connector and cable category.
Test the cable after termination.

Hubs vs Switches

Hub

A hub is a Layer 1 device. It repeats incoming bits out all other ports.

Consequences:

All ports share bandwidth.
All devices are in one collision domain.
Half-duplex behavior is common.
Less secure and inefficient.
Rare in modern networks.

Switch

A switch is a Layer 2 device. It learns source MAC addresses and forwards frames intelligently.

Consequences:

Each switch port is its own collision domain.
Full duplex is common.
Better performance than hubs.
Switches forward unknown unicast and broadcast traffic appropriately.
MAC address tables map MAC addresses to switch ports.

Exam contrast:

Hub repeats.
Switch forwards based on MAC address table.
Router forwards based on IP routes.

Connecting Switches

Switches can be connected to extend the network.

Important concepts:

Uplink ports were historically used to connect switches.
Crossover cables were historically needed for like devices.
Auto-MDIX lets ports automatically adjust transmit/receive pairs.
Trunks carry multiple VLANs between switches.
Avoid unmanaged loops unless loop prevention exists.

If connecting switches causes unstable network behavior, suspect loops, spanning tree issues, wrong cable, disabled port, speed/duplex mismatch, or VLAN/trunk configuration problems.

Module 3 Must Know

Ethernet is Layer 1/2 technology, but Ethernet frames are Layer 2.
Standard Ethernet MTU is 1500 bytes.
T568A and T568B define pinouts.
Hubs are Layer 1 repeaters.
Switches are Layer 2 forwarding devices.
Switches reduce collisions and improve performance.
Auto-MDIX reduces the need for crossover cables.

Module 4: Ethernet Standards

Big Picture

Ethernet standards describe speed, signaling, media type, and distance. For the exam, you must decode names like 100Base-TX, 1000Base-SX, and 10GBase-LR.

Reading Ethernet Names

Examples:

100Base-TX: 100 Mbps baseband Ethernet over twisted pair.
1000Base-T: 1 Gbps Ethernet over twisted pair.
1000Base-SX: 1 Gbps Ethernet over short-wavelength multimode fiber.
1000Base-LX: 1 Gbps Ethernet over long-wavelength fiber.
10GBase-SR: 10 Gbps short-range fiber.
10GBase-LR: 10 Gbps long-range fiber.

General decoding:

Number: Speed.
Base: Baseband signaling.
T: Twisted pair copper.
SX/SR: Short range, usually multimode fiber.
LX/LR: Long range, often single-mode fiber.

100BaseT

100Base-T is Fast Ethernet.

Know:

100 Mbps.
Common twisted pair version: 100Base-TX.
Usually uses two pairs.
Maximum copper segment commonly 100 meters.

Gigabit Ethernet

Common forms:

1000Base-T: 1 Gbps over twisted pair, commonly Cat 5e or better, up to 100 meters.
1000Base-SX: 1 Gbps over multimode fiber, shorter distances.
1000Base-LX: 1 Gbps over longer wavelength fiber, longer distances.

1000Base-T uses all four pairs in the cable.

10-Gigabit Ethernet

Common forms:

10GBase-T: 10 Gbps over twisted pair, usually Cat 6a for 100 meters.
10GBase-SR: 10 Gbps over short-range multimode fiber.
10GBase-LR: 10 Gbps over long-range single-mode fiber.
10GBase-ER: Extended reach single-mode fiber.

Exam idea:

For short rack/data center fiber links, SR is common.
For longer building/campus links, LR or ER may be appropriate.
For copper 10G to 100 meters, Cat 6a is the safe answer.

Transceivers

Transceivers convert between the network device and the physical medium.

Common types:

GBIC: Older, larger modular transceiver.
SFP: Small form-factor pluggable, commonly 1 Gbps.
SFP+: Commonly 10 Gbps.
QSFP/QSFP+: Higher density and higher speed options.

Important matching rules:

Match speed.
Match fiber type.
Match wavelength.
Match connector.
Match distance requirement.
Check device compatibility.

Duplex and Ethernet Connectivity

Half duplex:

Devices cannot send and receive at the same time.
Collisions are possible.
Associated with hubs and old Ethernet designs.

Full duplex:

Devices can send and receive simultaneously.
No collisions on the link.
Standard for modern switch connections.

Speed/duplex mismatch can cause poor performance, errors, late collisions, and intermittent connectivity.

Connecting Ethernet Scenarios

When troubleshooting Ethernet standards and connectivity, work from physical to logical:

Link light present?
Correct cable type and category?
Correct port and transceiver?
Within distance limit?
Matching speed and duplex?
VLAN/trunk/access settings correct?
Interface enabled?
Error counters increasing?

Common symptoms:

No link: bad cable, wrong transceiver, disabled port, power issue, physical damage.
Slow/intermittent: duplex mismatch, bad cable, excessive distance, EMI, failing NIC.
One VLAN cannot communicate: trunk/access/VLAN configuration issue.
Fiber link down: wrong fiber type, wrong polarity, dirty connector, incompatible optics.

Module 4 Must Know

Decode Ethernet standard names.
1000Base-T is 1 Gbps copper using four pairs.
10GBase-T often requires Cat 6a for full 100-meter support.
SR/SX imply shorter fiber reach; LR/LX imply longer reach.
Transceivers must match speed, media, connector, and distance.
Full duplex eliminates collisions on switched links.

Module 5: Installing a Physical Network

Big Picture

Structured cabling is the organized physical system that connects endpoints to network equipment. It includes work areas, wall jacks, horizontal cabling, patch panels, equipment rooms, racks, switches, and testing.

Structured Cabling

Structured cabling creates a predictable, maintainable physical network.

Common components:

Work area: User device location.
Wall outlet/jack: Endpoint connection point.
Horizontal cabling: Permanent cable run from work area to telecommunications room.
Patch panel: Termination point for horizontal cables.
Patch cable: Short cable from patch panel to switch, or device to wall jack.
Equipment room or telecommunications room: Network equipment location.
Rack/cabinet: Physical mounting structure.

Why it matters:

Easier troubleshooting.
Cleaner moves/adds/changes.
Reduced wear on permanent cable runs.
Better labeling and documentation.

Terminating Structured Cabling

Permanent cable is often punched down to patch panels and keystone jacks rather than crimped directly like a patch cord.

Tools and parts:

Punchdown tool.
110 block or patch panel.
Keystone jack.
Patch panel.
Cable stripper.
Cable tester/certifier.

Best practices:

Label both ends.
Maintain pair twists.
Avoid kinks and tight bends.
Keep copper away from EMI sources when possible.
Use cable management.
Test every run.

Equipment Room

The equipment room or telecom room houses switches, routers, patch panels, racks, UPS devices, and sometimes servers.

Good equipment room design includes:

Proper rack mounting.
Patch cable management.
Adequate cooling.
Clean power and UPS.
Labeling.
Physical security.
Grounding/bonding where required.
Space for growth.

Distribution Panels and Blocks

Alternative distribution hardware may include:

66 blocks: Older telephone-style punchdown blocks.
110 blocks: Common data/voice punchdown blocks.
Patch panels: Common Ethernet cabling termination points.
Fiber distribution panels: Organize and protect fiber terminations.

Exam clue:

Patch panels make moves and changes easier because switch ports connect to patch panel ports with short patch cables.

Testing Cable

Cable testing verifies that a run works and meets requirements.

Common tools:

Basic cable tester: Verifies continuity and wire map.
Wire map tester: Detects opens, shorts, crossed pairs, reversed pairs, and split pairs.
Cable certifier: Validates cable against a performance standard/category.
TDR: Time-domain reflectometer for copper distance/fault location.
OTDR: Optical time-domain reflectometer for fiber.
Toner and probe: Traces cable paths.
Loopback plug: Tests ports.
Multimeter: Electrical checks, not a full data cable certifier.

Common cable faults:

Open: Broken conductor or incomplete termination.
Short: Conductors touch.
Reversed pair: Pair polarity reversed.
Crossed pair: Pins mapped to wrong pair positions.
Split pair: Continuity may pass, but pair twist is wrong, causing crosstalk.
Excessive attenuation: Signal loss over distance or poor cable.
Crosstalk: Interference between pairs.

Troubleshooting Structured Cabling

Use a structured process:

Identify the symptom.
Check link lights.
Check the obvious physical items first.
Try a known-good patch cable.
Try a known-good port.
Test the permanent cable run.
Check termination and pinout.
Replace suspect cable if repair is not worth the time.

Common quick wins:

Reseat connectors.
Replace a patch cable.
Move to a known-good switch port.
Confirm the correct jack and patch panel port.
Confirm speed/duplex and VLAN.

Toner and Probe

A toner and probe helps trace an unlabeled cable. The toner sends a signal onto the cable, and the probe detects it at the other end or along the path.

Use cases:

Finding which cable goes to a wall jack.
Tracing unlabeled cables.
Identifying cable paths in a bundle.

Limitations:

It identifies/traces cable; it does not certify high-speed performance.
Use a cable tester or certifier for wiring and category compliance.

Wired Connection Scenarios

Common physical network scenarios:

No link light: Check cable, port, NIC, switch, power, transceiver, and termination.
Link light but no communication: Check IP configuration, VLAN, gateway, switch port state, and duplex/speed.
Intermittent link: Suspect damaged cable, marginal termination, EMI, distance, bad port, or loose connector.
Poor performance: Suspect duplex mismatch, cable category, excessive errors, congestion, or bad hardware.
Fiber link failure: Check polarity, connector cleanliness, transceiver compatibility, and fiber type.

Module 5 Must Know

Structured cabling separates permanent cable from patching.
Patch panels centralize terminations.
110 blocks are common punchdown hardware.
Cable certifiers verify category performance.
TDR is for copper fault distance; OTDR is for fiber.
Toner and probe traces cables but does not certify them.
Opens, shorts, split pairs, and bad terminations are common physical faults.

Exam Strategy

If A Question Mentions No Link

Think Layer 1 first:

Cable unplugged or damaged.
Wrong cable or connector.
Bad transceiver.
Disabled port.
Excessive distance.
Bad NIC or switch port.
Fiber polarity or dirty connector.

If A Question Mentions One Host Cannot Communicate

Check:

Link light.
IP address, subnet mask, gateway.
VLAN assignment.
Bad patch cable.
Switch port configuration.
MAC address table if switching issue is suspected.

If A Question Mentions Slow Or Intermittent Ethernet

Check:

Speed/duplex mismatch.
Bad cable or bad termination.
EMI.
Excessive cable length.
Interface errors.
Oversubscribed link.

If A Question Mentions Air Handling Space

Choose plenum-rated cable.

If A Question Mentions Long Distance Or EMI

Choose fiber optic cabling.

If A Question Mentions Tracing An Unknown Cable

Choose toner and probe.

If A Question Mentions Certifying Cat 6/Cat 6a

Choose cable certifier, not just a basic continuity tester.

Final Review Checklist

I can list all OSI layers in order.
I can identify the layer for MAC, IP, TCP/UDP, and applications.
I can explain encapsulation and decapsulation.
I can identify Ethernet frame fields and their purpose.
I can compare MAC and IP addressing.
I can explain broadcast vs unicast.
I can compare bus, ring, star, mesh, and hybrid topologies.
I can choose coax, twisted pair, or fiber for a scenario.
I can choose plenum or riser cable when given a building scenario.
I can explain T568A, T568B, straight-through, and crossover.
I can compare hubs and switches.
I can decode Ethernet standard names.
I can choose SFP/SFP+/QSFP and fiber standards for scenarios.
I can identify structured cabling components.
I can choose the right cable testing/tracing tool.
I can troubleshoot common wired connectivity symptoms.