NE-04: Physical Infrastructure

Learning Objectives

Identify copper and fiber cable types and their specifications
Recognize common connector types (RJ45, LC, SC, ST, F-type, BNC)
Explain T568A and T568B wiring standards
Describe physical installation best practices (IDF/MDF, rack layout, power, environmental)
Compare network topologies and their use cases

Copper Cabling

Copper cabling remains the backbone of most LANs. Twisted-pair cables use pairs of insulated copper wires twisted together to reduce electromagnetic interference (EMI). The two main types are UTP (Unshielded Twisted Pair) and STP (Shielded Twisted Pair).

UTP (Unshielded Twisted Pair) No additional shielding beyond the outer jacket. Most common in office environments. Lower cost, easier to install, sufficient for most deployments. Susceptible to EMI in industrial environments.

STP (Shielded Twisted Pair) Foil or braided shield around individual pairs or the entire cable bundle. Used in environments with high EMI (factories, near motors). Requires grounded connectors. Higher cost and stiffer cable.

Category	Max Speed	Max Distance	Common Use
Cat 5e	1 Gbps	100m	Legacy LAN
Cat 6	1-10 Gbps	55m (10G)	Modern LAN
Cat 6a	10 Gbps	100m	High-speed LAN
Cat 7	10 Gbps	100m	Shielded environments

Plenum vs PVC Jacket:

Plenum-rated cable (CMP) uses fire-retardant, low-smoke jacket material required for air-handling spaces (above drop ceilings, under raised floors). PVC/riser-rated cable (CMR) is cheaper but produces toxic fumes when burned -- never use PVC in plenum spaces.

Coaxial Cable: Uses a central copper conductor surrounded by insulation, a metallic shield, and an outer jacket. RG-6 is standard for cable TV and broadband ISP connections. RG-59 is thinner, used for short CCTV runs. Coax is largely legacy for networking but remains essential for cable internet (DOCSIS) and video distribution.

Fiber Optic Cabling

Fiber optic cables transmit data as pulses of light through a glass or plastic core. They are immune to EMI, support much longer distances than copper, and provide higher bandwidth. The two primary types differ in core size and light propagation.

Single-Mode Fiber (SMF) 9 micrometer core. Uses a laser light source. Single ray of light travels straight through the core. Supports distances up to 80km. Higher cost for transceivers. Used for WAN links, campus backbones, and long-haul connections.

Multimode Fiber (MMF) 50 or 62.5 micrometer core. Uses LED or VCSEL light source. Multiple rays of light bounce through the larger core (modal dispersion limits distance). Lower cost. Used for LAN backbones and data center interconnects.

Property	Single-Mode	Multimode
Core Size	9 micrometer	50 / 62.5 micrometer
Max Distance	Up to 80km	Up to 550m
Transceiver Cost	Higher	Lower
Use Case	WAN, long runs	LAN, data center
Jacket Color	Yellow (OS1/OS2)	Orange (OM1/OM2) or Aqua (OM3/OM4)

/* Multimode Fiber Grades */ OM1 62.5 micrometer core | Up to 275m at 1G | Orange jacket OM2 50 micrometer core | Up to 550m at 1G | Orange jacket OM3 50 micrometer core | Up to 300m at 10G | Aqua jacket OM4 50 micrometer core | Up to 400m at 10G | Aqua jacket /* Rule of thumb: - Fiber for runs over 100m or between buildings - Copper for horizontal runs to workstations (under 100m) - Fiber in environments with heavy EMI */

Connectors

Each cable type uses specific connectors. Knowing which connector matches which cable and application is essential for both the exam and field work.

RJ45 8-pin modular connector for Ethernet twisted-pair cables. The most common network connector. Used with Cat 5e/6/6a/7.

RJ11 4 or 6-pin modular connector for telephone lines. Smaller than RJ45. Still found on DSL modems and analog phone systems.

LC (Lucent Connector) Small form-factor fiber connector with a latch mechanism. Most common in modern data centers. Used with both SMF and MMF.

SC (Subscriber Connector) Square-shaped fiber connector with push-pull coupling. Larger than LC. Common in telecom and older installations.

ST (Straight Tip) Bayonet-style twist-lock fiber connector. Legacy connector, being replaced by LC and SC in most environments.

F-type Threaded coaxial connector used for cable TV, satellite, and cable internet (DOCSIS). Screw-on coupling.

BNC (Bayonet Neill-Concelman) Twist-lock coaxial connector. Legacy networking (10BASE2 thinnet). Still used in some CCTV and test equipment.

MTRJ (Mechanical Transfer RJ) Duplex fiber connector in a small form factor similar to RJ45. Contains both transmit and receive fibers in one connector.

SFP / SFP+ / QSFP Transceivers:

Small Form-factor Pluggable modules are hot-swappable transceivers that plug into switch/router ports. SFP supports up to 1 Gbps, SFP+ supports 10 Gbps, and QSFP+ supports 40 Gbps. They allow the same switch port to use different fiber or copper media by swapping the transceiver module.

Wiring Standards

The TIA/EIA-568 standard defines two wiring patterns for terminating twisted-pair cables into RJ45 connectors. Both use all 8 wires -- the difference is which color wire goes to which pin.

/* T568A Pin Assignments */ Pin 1: White/Green Pin 5: White/Blue Pin 2: Green Pin 6: Orange Pin 3: White/Orange Pin 7: White/Brown Pin 4: Blue Pin 8: Brown /* T568B Pin Assignments */ Pin 1: White/Orange Pin 5: White/Blue Pin 2: Orange Pin 6: Green Pin 3: White/Green Pin 7: White/Brown Pin 4: Blue Pin 8: Brown /* Key difference: T568A and T568B swap the green and orange pairs (pins 1-2 and 3-6) */

Straight-Through Cable Both ends use the SAME standard (both T568A or both T568B). Connects unlike devices: PC to switch, switch to router. The most common cable type.

Crossover Cable One end T568A, other end T568B. Connects like devices: switch to switch, PC to PC. Swaps transmit and receive pairs.

Auto-MDI/X:

Most modern switches and NICs support Auto-MDI/X, which automatically detects the connection type and internally swaps transmit/receive pairs as needed. This makes crossover cables largely unnecessary in modern networks, but you still need to know the concept for the exam.

Ethernet Standards

IEEE 802.3 defines the Ethernet standards that specify speed, cable type, and maximum distance. The naming convention follows: speed (in Mbps or Gbps) + BASE + media type abbreviation.

Standard	Speed	Cable	Max Distance
100BASE-TX	100 Mbps	Cat 5 UTP	100m
1000BASE-T	1 Gbps	Cat 5e UTP	100m
10GBASE-T	10 Gbps	Cat 6a UTP	100m
1000BASE-SX	1 Gbps	MMF	550m
1000BASE-LX	1 Gbps	SMF	5km
10GBASE-SR	10 Gbps	MMF	400m
10GBASE-LR	10 Gbps	SMF	10km

/* Naming convention breakdown */ 1000BASE-LX 1000 = Speed in Mbps (1 Gbps) BASE = Baseband signaling (single channel) L = Long wavelength (1310nm laser) X = Fiber optic /* Common suffixes: T = Twisted pair (copper) S = Short wavelength (850nm) -- multimode L = Long wavelength (1310nm) -- single-mode SR = Short reach LR = Long reach */

Physical Installation

Structured cabling and proper facility design are critical to a reliable network. The physical layout follows a hierarchical model from the service entrance to the wall jack.

MDF (Main Distribution Frame) Central point where outside cabling (ISP demarcation) enters the building and connects to the internal network backbone. Houses core switches and routers. Typically one per building.

IDF (Intermediate Distribution Frame) Secondary wiring closets on each floor or wing that connect back to the MDF via backbone cabling. Houses access-layer switches that serve end users. Multiple per building.

/* Standard 42U Rack Layout (bottom to top) */ Bottom (1U-8U): UPS, PDU, heavy equipment // Heavy items at the bottom for stability Middle (9U-28U): Servers, storage arrays // Most accessible area for maintenance Top (29U-42U): Switches, routers, patch panels // Network equipment generates less heat // Cable management easier from top /* 1U = 1.75 inches (44.45mm) of vertical rack space Standard full rack = 42U Half rack = 22U or 24U */

Hot/Cold Aisle Containment: Server racks are arranged so that cold air intakes face one aisle (cold aisle) and hot air exhausts face the opposite aisle (hot aisle). This prevents hot exhaust from recirculating into equipment intakes. Containment panels or doors seal the aisles for maximum efficiency.

Cable Management: Use horizontal and vertical cable managers, label both ends of every cable, maintain proper bend radius (no sharp kinks), use Velcro ties instead of zip ties (easier to modify), and keep power cables separated from data cables to prevent EMI.

TIA-606 Labeling Standard: Defines a uniform labeling scheme for cables, patch panels, outlets, and rooms. Every cable should be labeled at both ends with a unique identifier that traces back to documentation.

Power and Environmental

Network infrastructure requires clean, uninterrupted power and controlled environmental conditions. A failure in either can take down an entire site.

Online (Double-Conversion) UPS Always running on battery/inverter. Zero transfer time. Provides the cleanest power. Used for critical infrastructure like core switches and servers.

Line-Interactive UPS Uses an autotransformer to regulate voltage without switching to battery. 2-4ms transfer time. Good balance of protection and cost for network closets.

Standby (Offline) UPS Runs on utility power until it detects failure, then switches to battery. 5-12ms transfer time. Suitable for workstations and non-critical equipment.

PDU (Power Distribution Unit) Distributes power from a single source to multiple rack-mounted devices. Managed PDUs allow remote monitoring and per-outlet control. Essential for tracking power budgets.

Generators: Diesel or natural gas generators provide extended runtime during prolonged outages. UPS bridges the gap (30-60 seconds) while the generator starts. Regular testing under load is essential.

/* Environmental Controls */ Temperature: 64-75 F (18-24 C) per ASHRAE guidelines Humidity: 40-60% relative humidity // Too low = static discharge risk // Too high = condensation and corrosion Fire Suppression: Clean Agent (FM-200, Novec 1230) -- preferred for server rooms // Suppresses fire without damaging equipment // Safe for occupied spaces Pre-action Sprinkler -- requires two triggers (detector + sprinkler head) // Reduces accidental discharge risk // Water damage still possible // NEVER use standard wet-pipe sprinklers in a server room

Power over Ethernet (PoE):

PoE delivers DC power alongside data over standard Ethernet cables, eliminating the need for separate power supplies for devices like IP phones, wireless APs, and security cameras.

PoE Standard	IEEE	Max Power	Common Devices
PoE	802.3af	15.4W	IP phones, basic APs
PoE+	802.3at	30W	Pan-tilt cameras, advanced APs
PoE++	802.3bt	60-100W	Video conferencing, thin clients

Network Topologies

Network topology describes how devices are arranged and interconnected. Physical topology is the actual cable layout; logical topology describes how data flows.

Star Topology All devices connect to a central switch or hub. Most common LAN topology. Easy to add/remove devices. Single point of failure at the central device.

Mesh Topology Every device connects to every other device (full mesh) or most devices (partial mesh). Maximum redundancy. Common in WAN and core network designs. Expensive to implement.

Bus Topology All devices share a single backbone cable with terminators at each end. Legacy (10BASE2 coax). One cable break takes down the entire segment.

Ring Topology Devices form a closed loop. Data travels in one direction (or both in dual-ring). Used in FDDI and SONET. A break in the ring disrupts communication unless dual-ring is used.

Point-to-Point Direct connection between exactly two devices. WAN links between routers. Simple, dedicated bandwidth, no contention.

Hybrid Combination of two or more topologies. Most real-world networks are hybrid -- star topology in the LAN connected via mesh in the WAN.

/* Three-Tier Hierarchical Model */ Core Layer High-speed backbone, no packet filtering // Routers/L3 switches, redundant links Distribution Layer Policy enforcement, routing, filtering // L3 switches, ACLs, inter-VLAN routing Access Layer End-user connectivity, port security // L2 switches, PoE, VLAN assignment /* Spine-and-Leaf (Data Center) */ Spine Switches Every leaf connects to every spine Leaf Switches Connect directly to servers/storage // Equal-cost paths, predictable latency // Optimized for east-west traffic

Traffic Flow Directions:

North-South: Traffic entering or leaving the data center (client to server). Traditional three-tier handles this well. East-West: Traffic between servers within the data center (server to server). Spine-and-leaf is optimized for this pattern, which dominates modern workloads.

Key Takeaways

Cat 5e is the minimum for Gigabit Ethernet; Cat 6a is required for 10G at full 100m distance
Single-mode fiber = long distance (up to 80km); multimode fiber = short distance (up to 550m)
T568B is the most common wiring standard in the US; T568A is common internationally
Heavy equipment (UPS, PDU) goes at the bottom of the rack for stability
Always use clean agent fire suppression (FM-200, Novec 1230) in server rooms -- never wet-pipe sprinklers
PoE power budget must account for all connected devices -- plan for 802.3at (30W) or 802.3bt (60-100W) for modern APs