Chapter 5: Networking Fundamentals

A+ Core 1 — 220-1101 | Domains 2.2, 2.7, 3.1

Chapter 5:
Networking Fundamentals

Network types, topologies, the OSI model, cabling, connectivity devices, and IEEE standards. The conceptual foundation every A+ technician must own.

22 Slides Domains 2.2, 2.7, 3.1 OSI • Cabling • Devices • Standards Exam 220-1101

Slide 2 of 22

Network Types

Networks classified by geographic scope and purpose.

Type	Full Name	Scope	Example
LAN	Local Area Network	Single building or campus	Office network, home network
WAN	Wide Area Network	Large geographic area	The Internet, corporate backbone
PAN	Personal Area Network	Within reach of a person	Bluetooth devices, smartphone hotspot
MAN	Metropolitan Area Network	City or metro area	City-wide Wi-Fi, cable TV network
SAN	Storage Area Network	Dedicated storage network	Data center storage arrays
WLAN	Wireless Local Area Network	Local area via wireless	Wi-Fi network

SAN vs NAS

SAN provides block-level storage over a dedicated network. NAS provides file-level storage and appears as a network share. Do not confuse them on the exam.

Exam Tip

SAN relieves load on the main LAN, enables fast data access, and is easily expandable. It runs on a completely separate network fabric, not your regular Ethernet switch.

Slide 3 of 22

Network Access Models

Peer-to-peer workgroup vs. client-server domain environments.

Peer-to-Peer (Workgroup)

Decentralized administration. Each device manages its own accounts and shares. No dedicated server required. Best for SOHO environments with fewer than 10 devices. Easy to set up, difficult to secure at scale.

Client-Server (Domain)

Centralized administration via a domain controller (Active Directory). User accounts, policies, and permissions managed from one place. Required for enterprise environments. Enhanced security and auditing. Single sign-on across resources.

Component	Description
Servers	Dedicated (single purpose) or nondedicated (multiple roles)
Thick Client	Full OS, local processing, local storage
Thin Client	Minimal local processing, relies on server-side computing
NOS	Network Operating System — controls communication and data flow

Exam Association

Peer-to-peer = Workgroup = Decentralized. Client-server = Domain = Centralized. This pairing appears frequently as a recall question.

Slide 4 of 22

Network Topologies

Physical or logical arrangement of connected devices.

Topology	Description	Key Characteristic
Bus	All devices on a single backbone cable	Single point of failure; legacy
Star	All devices connect to a central hub or switch	Most common today; central device is SPOF
Ring	Devices in a circular chain; data travels one direction	Token Ring (legacy); any break halts the ring
Mesh	Every device connects to every other device	Highly redundant; used in WANs
Hybrid	Combination of two or more topologies	Most real-world networks

Key Point

Modern networks use Star topology with switches at the center. The central switch is a potential single point of failure (SPOF). Redundant switches solve this.

Physical vs Logical

Physical topology is the actual cable layout. Logical topology is how data flows. A network can be physically wired as a star but operate logically as a bus (legacy Ethernet on a hub).

Slide 5 of 22

The OSI Model: 7 Layers

Please Do Not Throw Sausage Pizza Away — Physical through Application.

7
Application
User interface and network services
HTTP, FTP, SMTP, DNS
6
Presentation
Data format, encryption, compression
SSL/TLS, JPEG, ASCII
5
Session
Establish, maintain, terminate connections
NetBIOS, RPC
4
Transport
End-to-end delivery, flow control, segmentation
TCP, UDP
3
Network
Logical addressing, routing
IP, ICMP, Routers
2
Data Link
Physical addressing, frames
MAC, Switches, NICs
1
Physical
Cables, signals, bits
Ethernet, Hubs, Cables

Slide 6 of 22

OSI: Devices & Encapsulation

Which device lives at which layer, and how data moves through the stack.

Layer 1 Devices

Hubs, repeaters, cables, physical connectors. Operate on raw bits only. No addressing awareness. A hub broadcasts every signal out every port — no filtering, all collision domain.

Layer 2 Devices

Switches and bridges. Read MAC addresses from frames to make forwarding decisions. Each switch port is its own collision domain. MAC address table built dynamically by observing source MACs.

Layer 3 Devices

Routers. Read IP addresses from packets. Route traffic between networks. Each router interface is a separate broadcast domain. Required to move packets between different subnets.

Encapsulation (Sending)

Data travels DOWN the stack. Each layer adds its own header (encapsulation). Application data becomes a segment at Layer 4, a packet at Layer 3, a frame at Layer 2, and bits at Layer 1.

Decapsulation (Receiving)

Data travels UP the stack on receipt. Each layer strips its header (decapsulation) and passes the payload to the layer above. This is why the OSI model is a conceptual framework, not physical hardware.

Slide 7 of 22

Network Cabling: Coaxial

RG-6 and RG-59 — coax standards and connectors for cable broadband.

Type	Use	Core Diameter	Max Distance
RG-6	Digital cable TV, satellite, cable modems	1.0 mm	304 m (1,000 ft)
RG-59	Analog cable TV	0.762 mm	228 m (750 ft)

F-Type Connector

Screw-on connector. Most common for cable TV and cable modems. The center conductor of the coax itself serves as the pin. Must be tightened finger-tight to ensure good signal. Found on all residential cable installations.

BNC Connector

Bayonet Neill-Concelman. Twist-lock connection. Used on legacy 10Base2 Ethernet (thinnet), test equipment, and security cameras. Quick connect/disconnect. Still found in professional video and RF test gear.

Exam Tip

RG-6 is the current standard for cable internet connections. RG-59 is older, thinner, and less shielded. If a cable internet install is failing at distance, check whether RG-59 was used instead of RG-6.

Slide 8 of 22

Twisted Pair: Categories

Cat 5 through Cat 7 — speeds, distances, and what changed.

Category	Ethernet Spec	Max Speed	Max Distance	Note
Cat 5	100BaseT	100 Mbps	100 m	Legacy, 2 pairs used
Cat 5e	1000BaseT	1 Gbps	100 m	Enhanced, 4 pairs, reduced crosstalk
Cat 6	10GBaseT	10 Gbps	55 m at 10G / 100 m at 1G	Spline separator inside
Cat 6a	10GBaseT	10 Gbps	100 m	Augmented; larger diameter
Cat 7	10GBaseT	10 Gbps	100 m	Individually shielded pairs

The 100-Meter Rule

All twisted pair categories support a maximum segment length of 100 meters, EXCEPT Cat 6 running at 10 Gbps, which is limited to 55 meters. Cat 6a restores the full 100 m at 10G.

UTP vs STP

UTP (Unshielded) is most common — no shielding. STP (Shielded) adds foil or braid shielding to reduce EMI. Plenum-rated cable has a fire-resistant jacket required in air-handling spaces (above drop ceilings, raised floors).

Slide 9 of 22

Wiring Standards: T568A & T568B

Pin assignments for RJ-45 connectors and cable types.

Pin	T568A	T568B
1	White/Green	White/Orange
2	Green	Orange
3	White/Orange	White/Green
4	Blue	Blue
5	White/Blue	White/Blue
6	Orange	Green
7	White/Brown	White/Brown
8	Brown	Brown

Straight-Through Cable

Same standard on both ends (T568B–T568B). Connects unlike devices: computer to switch, switch to router. Most common patch cable type in use today.

Crossover Cable

Different standards each end (T568A one end, T568B the other). Connects like devices: computer to computer, switch to switch. Modern switches use Auto-MDI/MDIX to auto-detect, making crossover cables largely obsolete.

Slide 10 of 22

Fiber Optic Cable

Single-mode vs. multimode, and common fiber connectors.

Type	Core Size	Speed	Distance	Light Source
MMF (Multimode)	50–62.5 microns	1–10 Gbps	Up to 550 m	LED
SMF (Single-mode)	8–10 microns	10+ Gbps	Up to 40+ km	Laser

ST Connector

Straight Tip. Twist-lock, round bayonet style. Older standard, still found in legacy installations and some campus networks.

SC Connector

Subscriber Connector. Square push/pull snap-in design. Very common in data centers and enterprise networking. Duplex SC has two connectors side by side.

LC Connector

Lucent Connector. Small form factor (half size of SC). The most widely deployed connector today. Used in SFP/SFP+ transceivers. Latching tab for secure connection.

Exam Tip

Single-mode = Small core = Laser = Longer distance. Multimode uses LED and is for shorter distances. Fiber has zero EMI susceptibility — ideal for industrial environments.

Slide 11 of 22

Connector Reference

All major network connectors and their correct media type.

Connector	Media Type	Pins/Notes
RJ-45	Twisted pair Ethernet	8 pins; used with Cat 5/5e/6/6a/7
RJ-11	Telephone / DSL	6-pin housing, 2 or 4 pins used; smaller than RJ-45
F-Type	Coaxial (cable TV, modem)	Screw-on; coax center conductor is the pin
BNC	Coaxial (legacy, test equipment)	Twist-lock; 10Base2 (thinnet)
ST	Fiber optic	Twist-lock round; older fiber installations
SC	Fiber optic	Square push/pull; common in enterprise
LC	Fiber optic	Small form factor; most common today

A technician is handed a cable with a rectangular square snap-in connector and asked to identify it. The housing is plastic and beige. It must be an SC fiber connector. If it were smaller with a latch tab, it would be LC. If it had 8 metal contacts and was larger, it would be RJ-45.

Slide 12 of 22

Connectivity Devices: Layer 1 & 2

Hubs, repeaters, bridges, and switches — what each does and at which layer.

Hub (Layer 1 — Obsolete)

Broadcasts every received signal out every port. No MAC address awareness. All ports share one collision domain. Half duplex only. Replaced by switches in the late 1990s. Still appears on A+ exams as a negative example of poor design.

Repeater / Extender (Layer 1)

Regenerates and amplifies a signal to extend distance. No filtering or intelligence. Used to overcome the 100-meter cable limit on copper segments. Wireless range extenders operate on a similar principle at Layer 2.

Bridge (Layer 2)

Connects two network segments. Filters traffic by MAC address. Only two ports. The precursor to the multi-port switch. Still referenced in the exam for its SPOF-reducing role when segmenting collision domains.

Switch (Layer 2)

Forwards frames based on destination MAC address from its CAM table. Each port is its own collision domain. Supports full duplex. Unmanaged: plug-and-play. Managed: supports VLANs, QoS, port mirroring, SNMP.

Slide 13 of 22

Connectivity Devices: Layer 3+

Routers, access points, firewalls, modems, and PoE.

Device	OSI Layer	Function
Router	Layer 3	Forwards packets by IP address; connects different networks; each interface is a broadcast domain boundary
Access Point (WAP)	Layer 2	Wireless bridge to wired network; does not route; extends collision domain wirelessly
Firewall	Layers 3–7	Filters traffic by rules (IP, port, protocol, application); security perimeter device
Modem	Layer 1–2	Modulates/demodulates signals (digital ↔ analog) for DSL or cable connections to ISP

PoE (Power over Ethernet)

Delivers both data and electrical power over a single Cat 5e/6 cable. Used for WAPs, IP cameras, IP phones, and small switches. PoE switch or injector required on the sourcing end. Max power: PoE = 15.4 W; PoE+ = 30 W; PoE++ = 60–100 W.

ONT (Optical Network Terminal)

Converts fiber optic signal to copper Ethernet at the customer premises. Required for FTTH (Fiber to the Home) ISP connections. The ONT is the fiber-equivalent of a cable modem.

Slide 14 of 22

Patch Panels & Structured Cabling

Termination, organization, and the path from wall jack to switch.

Patch Panel

Passive device that terminates permanent wall wiring to RJ-45 ports on the front. Short patch cables then run from panel ports to switch ports. Allows flexible moves, adds, and changes without re-running cable.

66 / 110 Block

Punchdown termination blocks. 66 block is legacy telephony (voice). 110 block is the standard for data cabling. Cable pairs are pushed into slots with a punchdown tool, trimming excess wire simultaneously.

Cable Run Path

Wall jack → permanent horizontal run (max 90 m) → patch panel in IDF/MDF → patch cable to switch. Total segment including patch cables must stay within 100 m. Horizontal cabling is the most common failure point.

MDF vs IDF

MDF (Main Distribution Frame): the main wiring closet where the ISP connection and core switches live. IDF (Intermediate Distribution Frame): secondary closets on each floor or wing, connected back to the MDF via backbone cabling (typically fiber).

Slide 15 of 22

Network Interface Cards

NIC hardware, MAC addresses, duplex, and driver requirements.

NIC Basics

The physical interface between a device and the network. Wired NICs use RJ-45. Wireless NICs use antennas. PCIe x1 slot for add-in cards. Onboard NICs are soldered to the motherboard. Most modern NICs support 10/100/1000 Mbps auto-negotiation.

MAC Address

48-bit hardware address burned into the NIC at manufacturing. Written in hex: XX:XX:XX:XX:XX:XX. First 24 bits = OUI (Organizationally Unique Identifier) identifying the manufacturer. Last 24 bits = device-specific. Operates at Layer 2. Cannot be routed across networks.

Duplex & Speed

Half duplex: transmit or receive, not both simultaneously (hubs). Full duplex: transmit and receive simultaneously (switches). Duplex mismatch between NIC and switch causes poor performance. Auto-negotiation resolves this in most cases, but manual configuration may be needed.

NIC Drivers

Software component that allows the OS to communicate with the NIC hardware. Out-of-date or missing drivers cause no network connectivity, limited speed, or random disconnections. Device Manager in Windows shows driver status. Always download NIC drivers from the manufacturer's site.

Slide 16 of 22

IEEE 802 Standards

802.3 Ethernet and 802.11 Wi-Fi — the two standards every A+ tech must know cold.

IEEE 802.3 — Ethernet

Defines wired LAN communication over twisted pair and fiber. Uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection). Devices listen before transmitting, detect collisions, back off randomly, and retransmit. Full duplex on switches eliminates collisions entirely.

IEEE 802.11 — Wi-Fi

Defines wireless LAN communication. Uses CSMA/CA (Collision Avoidance) because wireless nodes cannot detect collisions while transmitting. Uses RTS/CTS (Request to Send / Clear to Send) to reserve the medium before transmitting data.

Standard	Method	Reasoning
802.3 Ethernet	CSMA/CD — Collision Detection	Wired: can detect a voltage change when two signals collide
802.11 Wi-Fi	CSMA/CA — Collision Avoidance	Wireless: cannot detect collisions while transmitting; must avoid them

Memory Trick

Wired = CD (Detection). Wireless = CA (Avoidance). Wireless avoids because it cannot detect. The D and A are the only letters that change.

Slide 17 of 22

Ethernet Naming Conventions

Reading the BaseX naming system: speed, signaling, and medium.

Name Breakdown

Format: [Speed][Signaling][Medium]. Example: 100BaseTX = 100 Mbps / Baseband / Twisted pair. 1000BaseSX = 1 Gbps / Baseband / Short-wavelength fiber. Always baseband on modern Ethernet (full bandwidth on single channel).

T vs F vs S/L

"T" = Twisted pair copper. "F" = Fiber optic (generic). "S" = Short-range fiber (multimode). "L" = Long-range fiber (single-mode). "X" = encoding variant. Knowing T vs fiber lets you identify the physical medium from the standard name alone.

Common Names

10BaseT (10 Mbps, Cat 3+). 100BaseTX (100 Mbps, Cat 5+). 1000BaseT (Gigabit, Cat 5e+). 10GBaseT (10G, Cat 6/6a). 10GBaseSR (10G, MMF). 10GBaseLR (10G, SMF, 10 km). These appear directly on exam questions.

Exam Tip

The number before "Base" is speed in Mbps or Gbps. All current Ethernet is baseband. The suffix tells you the medium. 1000BaseT = Gigabit over copper. 10GBaseSR = 10G over short-range multimode fiber.

Slide 18 of 22

Managed vs. Unmanaged Switches

When to use each type and what capabilities managed switches add.

Unmanaged Switch

Plug-and-play. No configuration interface. Automatically learns MAC addresses. Fixed behavior — cannot configure VLANs, QoS, or port settings. Best for small networks and home use where simplicity outweighs control. No administrative access means no SNMP monitoring either.

Managed Switch

Web interface or CLI for configuration. Supports VLANs (logical network segmentation), QoS (quality of service prioritization), port mirroring (traffic analysis), SNMP (network monitoring), STP (loop prevention), link aggregation, and port security by MAC address.

Feature	Unmanaged	Managed
VLANs	No	Yes
QoS	No	Yes
SNMP	No	Yes
Port Mirroring	No	Yes
STP (Loop Prevention)	Basic only	Full STP/RSTP

Slide 19 of 22

VLAN Concepts

Virtual LANs segment a single physical switch into multiple isolated broadcast domains.

What VLANs Do

Logically isolate groups of ports on a single switch as if they were on separate physical switches. Devices on VLAN 10 cannot communicate with devices on VLAN 20 without a router or Layer 3 switch. Reduces broadcast traffic and improves security.

Access vs. Trunk Ports

Access port: assigned to one VLAN; connects end devices (computers, printers). Trunk port: carries traffic for multiple VLANs simultaneously using 802.1Q tagging; used between switches and between a switch and a router for inter-VLAN routing.

VLAN Use Cases

Separate guest Wi-Fi from corporate LAN. Isolate VoIP traffic onto its own VLAN for QoS. Segment accounting department from general staff. Contain a compromised device from spreading laterally. All on the same physical hardware.

Inter-VLAN Routing

Traffic between VLANs must pass through a router (or a Layer 3 switch that can route). The "router-on-a-stick" method uses a single trunk uplink from switch to router with subinterfaces per VLAN. Each subinterface serves as the default gateway for its VLAN.

Slide 20 of 22

Alternative Network Media

Non-standard but exam-relevant connectivity options.

Ethernet over Power (HomePlug)

Uses existing electrical wiring to carry network data. Adapters plug into standard AC outlets. Useful when running new cable is impractical. Speeds vary significantly based on wiring quality and electrical noise. Not suitable for mission-critical applications.

Ethernet over HDMI

HDMI 1.4 and later includes an Ethernet channel (HEC — HDMI Ethernet Channel) within the cable. Allows connected AV devices to share a network connection. Rarely used in practice but can appear on the exam as an alternative media question.

Direct Burial Cable

Twisted pair or coaxial with a waterproof outer jacket rated for underground outdoor installation. Does not require conduit. Used for outdoor runs between buildings. Cat 5e/6 direct burial rated for 600 V. Different from standard outdoor-rated cable.

Cable / DSL Modems

Cable modem: connects to ISP via coaxial RG-6 using DOCSIS standard. DSL modem: connects over telephone line; distance from the central office directly limits speed. Both convert the ISP's signal to standard Ethernet for the local network.

Slide 21 of 22

Networking Troubleshooting Scenarios

Applying chapter knowledge to real-world problems.

10G Link at 1G Speed

Cat 6 cable run is 70 meters. Cat 6 only supports 10G at 55 meters. Replacing with Cat 6a resolves the limitation. Alternatively, run a fiber link. The port negotiates down to 1G because the medium cannot sustain 10G at that distance.

No Link Light on Switch

Check cable termination at both ends (flipped pair, bad crimp). Swap with a known-good patch cable. Try a different switch port. Use a cable tester to identify which pair is open or miswired. 90% of no-link issues are physical layer (Layer 1) problems.

Intermittent Drops

Duplex mismatch: NIC set to full duplex, switch port at half duplex. Set both ends to auto-negotiate or manually match. Check for bent RJ-45 pins. Also check for excessive cable length — link errors increase significantly beyond 100 meters.

A user cannot reach file shares on a different department's server, but can ping the default gateway. The network uses VLANs. The user's VLAN is correct. The router ACL is blocking inter-VLAN traffic to the file server's subnet — a Layer 3 routing/policy issue, not a cable or switch problem.

Slide 22 of 22 — Chapter 5 Complete

Chapter 5 Summary

Eight key takeaways from Networking Fundamentals.

1

Network types by scope: PAN (personal), LAN (local), MAN (metro), WAN (wide). SAN is a separate storage network; NAS is file-level storage on the LAN.

2

OSI 7 layers top-down: Application, Presentation, Session, Transport, Network, Data Link, Physical. Mnemonic: Please Do Not Throw Sausage Pizza Away (bottom-up).

3

Layer devices: Hub = Layer 1. Switch = Layer 2 (MAC). Router = Layer 3 (IP). Firewall = Layers 3–7. This association is tested heavily.

4

Twisted pair 100-meter rule: all categories max at 100 m, except Cat 6 at 10G which is limited to 55 m. Cat 6a restores 100 m at 10G.

5

Fiber: Single-mode = small core + laser + long distance (40+ km). Multimode = larger core + LED + short distance (550 m). LC connector is the most common today.

6

Wired = CSMA/CD, Wireless = CSMA/CA. Wired detects collisions; wireless avoids them. Only the D vs. A changes between the two standards.

7

T568B is the dominant wiring standard. Straight-through (T568B both ends) connects unlike devices. Crossover (T568A one end) connects like devices; Auto-MDI/MDIX on modern switches makes crossover cables obsolete.

8

VLANs segment a single switch into isolated broadcast domains. Access ports carry one VLAN. Trunk ports carry multiple VLANs using 802.1Q tagging. Inter-VLAN traffic requires routing.