Every unit from the Block 1 course, in one place — safety, publications, OSI, ports & protocols, IP addressing, wireless, media, troubleshooting, and network monitoring, each with its own quiz.
// Objective 2a-b · Grounding & Bonding
Grounding connects equipment to the earth so dangerous currents have somewhere safe to go. It has three jobs: personnel safety (diverting dangerous current away from people), equipment protection (preventing transient voltage spikes from damaging gear), and electrical noise reduction (cutting down EMI, like a vacuum cleaner causing static on a TV).
The facility ground system has three subsystems: the earth electrode subsystem (rods driven into the dirt), the equipment fault protective subsystem (the "safety ground" that trips breakers/fuses on a fault), and the signal reference subsystem (the "signal ground" that keeps all equipment on the same voltage reference, or "equipotential plane").
Bonding creates a low-impedance path between two metal surfaces so differences in voltage can't build up and cause shocks, fires, or signal problems. Direct permanent bonds (welded/brazed) are never meant to come apart. Direct semi-permanent bonds (bolts, clamps, nuts) can be disassembled and are common in mobile/deployed setups. Indirect bonds use straps for things that move often, like doors.
Bonding dissimilar metals (like copper to steel) causes corrosion — the bigger the difference in "corrosion potential," the faster it corrodes — so techs avoid mixing metals when they can.
// Objective 2c · Electrostatic Discharge (ESD)
// Objective 2d · Physical Security
Control Area — needs some form of ID to enter (a base gate, a server room). Restricted Area — needs a special access badge and a valid purpose to be there (a flight line, an NSA facility). No-Lone Zone — you can never be there alone; a companion is required (e.g., burning/shredding classified material always takes two people).
Active measures deter, detect, and react — fences, cameras, guard dogs, armed patrols. Passive measures discourage threats through design — landscaping, lighting, and limiting the number of entrances.
// Objective 2e · Workplace Safety
Most mishaps trace back to one of three factors: psychological (distraction, rushing, insufficient training), physical (fatigue, medication, alcohol/drugs, taking shortcuts), or organizational (understaffing, production pressure over safety). PPE is the least preferred hazard control — engineering the hazard out (substitution, isolation, better procedures) comes first.
Electrical safety: it's current, not voltage, that kills — a common misconception is that voltage alone is dangerous. "DANGER HIGH VOLTAGE" signs mean 600V or more; never work alone around high voltage. Fuses and breakers protect equipment, not people. RF radiation hazards are invisible and may not be felt until damage is already done — the same principle a microwave oven uses to cook food.
Warnings protect personnel; cautions protect equipment and property. Always use current technical data and never skip a safety step, no matter how small.
// Quiz yourself · Unit 2
// Objective 3a · What publications are and why they matter
Some publications are directive (they tell you how a task must be done); others provide guidance. All of them convey information about a subject. Always verify you're using the current version — a downloaded copy on your desktop can silently go out of date, and you won't be notified when it changes.
// The publication families — click to expand
// Objective 3b · Using publications correctly
Check the source website (E-Pubs for AF publications, esd.whs.mil for DoD issuances) before relying on a downloaded copy — publications can be revised or rescinded without notifying you. If the guidance in a publication seems wrong, don't just skip it: contact the Office of Primary Responsibility (OPR) listed on the publication to get it corrected.
// Quiz yourself · Unit 3
// Objective 4a · The 7 layers — click any layer to expand
Closest to the end user — web browsers, email clients, and apps live here. It identifies communication partners, checks quality of service, handles authentication, and defines data-syntax constraints.
Translates data between application and network format, and vice versa — encryption/decryption and compression happen here, and it renders the underlying code into words, pictures, video, or audio.
Establishes, manages, and terminates connections between applications on different devices — the continuous back-and-forth of a session.
End-to-end error recovery, flow control, and complete data transfer. Decides how much data to send and confirms it all arrived — resending anything lost.
Finds the best path for data using IP addresses. Handles routing, forwarding, addressing, and error handling — every packet gets a source and destination IP.
Delivers between two directly connected devices using MAC addresses — a hardware ID burned into every NIC that never changes. Data here is called a frame. Splits into two sub-layers: MAC (who may transmit) and LLC (frame sync, flow control, error checking).
Cables, radio waves, electrical signals — everything becomes bits (1s and 0s) sent through a physical medium. When something breaks, technicians check here first: is it plugged in, powered, and intact?
// PDU name at each layer
| Layers | Data unit | Key devices |
|---|---|---|
| 7–5 Application/Presentation/Session | Data | Computer |
| 4 Transport | Segment | Computer |
| 3 Network | Packet | Router |
| 2 Data link | Frame | Switch |
| 1 Physical | Bits | Cable / NIC |
// Memory tricks
Top to bottom (7→1): Awesome Programmers Should Teach New Developers Patiently
Bottom to top (1→7): Please Do Not Throw Sausage Pizza Away
Data travels down the stack when sending (encapsulation, adding a header at each layer) and back up when receiving (decapsulation).
// Quiz yourself · Unit 4
// Objective 5a · What is a protocol?
Think of a protocol like a shared language — if two devices support the same protocol, they can talk regardless of manufacturer. An iPhone can email an Android because they both follow the same email protocol rules.
// Common protocols — click to expand
// Objective 5b · TCP vs UDP
Use TCP when every bit must arrive: Telnet, SMTP, FTP, HTTP. Use UDP when speed beats perfection: VoIP, video streaming, gaming, DNS, DHCP, SNMP, RIP.
// Objective 5c · Ports
IANA (Internet Assigned Numbers Authority) manages official port assignments. Three ranges: Well-Known (0–1,023) — the ones to memorize; Registered (1,024–49,151) — assigned by IANA for specific services but usable generally; Dynamic/Ephemeral (49,152–65,535) — temporary, assigned per-session then released.
| Port(s) | Protocol | Transport |
|---|---|---|
| 20 & 21 | FTP | TCP |
| 23 | Telnet | TCP |
| 25 | SMTP | TCP |
| 53 | DNS | UDP |
| 67 | DHCP | UDP |
| 80 | HTTP | TCP |
| 161 | SNMP | UDP |
| 443 | HTTPS | TCP |
| 520 | RIP | UDP |
// Quiz yourself · Unit 5
// Number systems — the foundation
Underneath, everything is binary. Converting between decimal, binary, and hexadecimal uses the weighted-table method (find the largest place value that divides in, subtract, repeat) or, for binary↔hex, the quick 8-4-2-1 inspection method since one hex digit always equals exactly 4 binary bits.
Want to practice the actual conversions step by step? Use the Number Base Converter tool — it shows the full weighted-table breakdown for every direction (decimal↔binary↔hex).
// Objective 6a · IPv4
An IPv4 address is 32 bits written as four 8-bit octets separated by dots (e.g. 205.112.45.60), each octet ranging 0–255. Every address has a Network Number (which network it's on) and a Host Number (which specific device on that network).
| Class | 1st octet range | Address format | Use |
|---|---|---|---|
| A | 1–126 | Network.Host.Host.Host | Large networks (126 nets, ~16.7M hosts each) |
| B | 128–191 | Network.Network.Host.Host | Medium networks (~16,384 nets, ~65,534 hosts each) |
| C | 192–223 | Network.Network.Network.Host | Small networks (~2M nets, 254 hosts each) |
| D | 224–239 | — | Reserved for multicast |
| E | 240–255 | — | Reserved for research & development |
Special-purpose ranges to know
| Range | Purpose |
|---|---|
| 10.0.0.0 – 10.255.255.255 | Private (RFC 1918) |
| 172.16.0.0 – 172.31.255.254 | Private (RFC 1918) |
| 192.168.0.0 – 192.168.255.254 | Private (RFC 1918) |
| 169.254.0.0/16 | APIPA — self-assigned when DHCP fails |
| 127.0.0.0/8 | Loopback — 127.0.0.1 talks to yourself, used for testing |
Private addresses work like phone extensions: your organization has one public address the internet sees, and hundreds of private addresses behind it that only matter internally.
// Objective 6b · IPv6
IPv6 addresses are 8 groups of 4 hex digits separated by colons, e.g. 2001:0DB8:85A3:0000:0000:8A2E:0370:7D34. There are no classes in IPv6. The loopback is ::1/128; multicast is designated ff00::/8.
// Quiz yourself · Unit 6
// Objective 7a · Wireless fundamentals
An AP connects to a wired switch/router and broadcasts a Wi-Fi signal to a coverage area. Under IEEE 802.11, a group of wireless devices sharing settings is a "service set," identified by an SSID. Each individual AP's own service set is a BSSID (using the AP's MAC address as the ID); the combined name across all APs in a network (what you see when scanning for Wi-Fi) is the ESSID.
Wireless network types
| Type | Range | Typical use |
|---|---|---|
| WPAN | ~10m | Bluetooth, Infrared — devices around one person |
| WLAN | ~100m | Wi-Fi (802.11) — home, office, campus buildings |
| WMAN | ~31 miles / 50km | Connecting buildings across a campus or metro area |
| WWAN | Cities/regions/countries | Cellular (GSM, CDMA, LTE) — phone carrier networks |
| Hybrid | — | One router serves both wired (Ethernet) and wireless clients |
| Ad Hoc | — | Decentralized, device-to-device, no AP or router required |
Advantages: mobility/collaboration, roaming without dropped connections, reaching hard-to-wire areas.
Disadvantages: slower than wired, less reliable (interference from phones, microwaves, metal), weaker security (anyone in range can try to intercept), and reduced management control (rogue personal devices connecting).
// Objective 7b · Wireless standards
| Standard | Band | Max speed (theoretical) |
|---|---|---|
| 802.11ax (Wi-Fi 6) | 2.4 / 5 GHz | 2.4 Gbps |
| 802.11ac wave 2 | 5 GHz | 1.73 Gbps |
| 802.11ac wave 1 | 5 GHz | 866.7 Mbps |
| 802.11n | 2.4 / 5 GHz | 450 Mbps |
| 802.11g | 2.4 GHz | 54 Mbps |
| 802.11a | 5 GHz | 54 Mbps |
| 802.11b | 2.4 GHz | 11 Mbps |
Before transmitting, a wireless station listens ("senses") the channel; if clear, it waits a random interval and checks again before sending — since only one station can use the frequency at a time (half-duplex). This is the wireless counterpart to wired Ethernet's CSMA/CD (Collision Detection, which reacts to collisions that already happened rather than avoiding them).
// Objective 7c · Access point types
| Type | Description |
|---|---|
| Autonomous | Self-contained — its own built-in Wireless LAN Controller (WLC), no external controller needed. Good for small networks. |
| Multifunction | Combines AP + switch + router (+ sometimes modem) in one box — a typical ISP-provided home router. |
| Lightweight (LWAP) | Makes no forwarding decisions itself — forwards every frame to a central WLC, which decides whether to forward or discard it. |
| Rogue | Installed without authorization (accidentally or maliciously) — a real security risk since it can enable man-in-the-middle attacks. |
// Objective 8a · Copper cable categories
Unshielded Twisted-Pair (UTP) — 4 twisted pairs of copper wire, the most common and economical networking cable. Twisting reduces EMI/RFI without extra shielding. Shielded Twisted-Pair (STP) adds a metallic foil/braid layer around the pairs for extra EMI protection — more expensive, less flexible, harder to install, so used less often. ANSI cable categories (CAT5, CAT6, etc.) — a higher category number means better noise reduction, lower attenuation, and higher bandwidth.
Straight-through connects unlike devices (PC→switch) — both ends match the same standard (T-568A or T-568B). Crossover connects like devices (switch→switch) — TX/RX pins are swapped, so one end is T-568A and the other T-568B. Rollover (console cable) mirrors every pin — used to connect a PC to a switch/router's console port for configuration.
// Objective 8b · Fiber
Fiber carries light, not electricity, so it's immune to electromagnetic (EMF) monitoring — nothing radiates out for an attacker to intercept.
// Objective 8c · Wireless transmission media
Light transmissions use focused laser beams needing clear line-of-sight — offer some security through limited interception area, but rain/fog/snow degrade the signal. Radio waves use microwave frequencies (1–20 GHz) and come in two flavors: Fixed frequency (easy to monitor/jam once the frequency is known, e.g. a radio station) and Spread spectrum (varies across a frequency band in a repeated pattern — harder to jam, though a determined attacker can still learn the pattern).
// Quiz yourself · Units 7–8
// Objective 9a · The 6-step troubleshooting methodology
Gather info from the user, logs/error messages, and personal observation. Symptoms are not the problem — question the user calmly and without blame.
List likely causes, most to least likely. Question the obvious first. Use Top-Down or Bottom-Up OSI-layer approaches to narrow it down.
Confirm or disprove your leading theory. If disproved, go back to step 1 or 2. Escalate if it's outside your scope.
Write out the fix, especially for complex problems. Consider side effects — if it takes down a server, schedule around user impact.
Confirm the whole system works, not just the original symptom. Apply Root Cause Analysis (RCA) to prevent recurrence, not just patch the surface.
Record findings, actions, and outcomes — including what didn't work — so the next tech doesn't repeat your steps.
// Objective 10a · Hardware troubleshooting tools
| Tool | What it does |
|---|---|
| Crimper | Attaches connectors (e.g. RJ-45) to cable ends using mechanical pressure |
| Cable tester | Checks continuity and pinout by connecting both cable ends to the tester |
| Loopback plug | Sends a device's signal back to itself to self-test a port |
| Punch-down tool | Terminates a wire into a terminal block's slot |
| OTDR | Finds breaks/splices/defects in fiber by measuring reflected light and distance |
| Optical power meter | Measures fiber signal strength to detect excess attenuation |
| Tone generator | "Fox and hound" — emits an audible tone a probe follows to trace a cable |
| Digital multimeter | Measures voltage, resistance, and continuity to isolate faulty components |
// Software tools & CLI commands
| Tool / command | What it does |
|---|---|
| Port scanner | Finds open ports/services on a host |
| Protocol analyzer | Captures/inspects individual packets |
| Bandwidth tester | Measures connection speed via sample up/downloads |
| arp | Views/edits the IP→MAC address cache |
| ping | Sends ICMP Echo Requests to test connectivity, loss, and latency |
| tracert | Traces the hop-by-hop route to a destination using increasing TTL values |
| ipconfig | Shows local IP, subnet mask, gateway, DNS settings |
| netstat | Shows active connections, protocols, and states |
| nslookup | Resolves domain names ↔ IP addresses |
// Objective 10b · Connectivity test sets
A connectivity test set checks proper transmission/reception between devices — for example, unplugging a misbehaving printer's Ethernet cable and plugging it into the test set to confirm the signal is strong and consistent. Some are simple continuity testers; others also test switch connectivity, Ping, and Power over Ethernet (PoE), comparing results against IEEE 802.3 transmission parameters (10BASE-T through 10GBASE-T).
// Quiz yourself · Units 9–10
// Objective 11a · Why monitor a network?
When networks fail, the flow of information business operations depend on just stops. Network Monitoring Systems (NMSs) watch for problems from overloaded/crashed servers, failed connections, or device issues — tracking availability, response time, and whether routes are optimal.
Monitoring also flags suspicious/unauthorized activity: network scanning, repeated connection attempts from unknown sources, unusual traffic, or root/user-level access by unauthorized individuals.
// The 5 functions of an NMS
Find every device on the network and auto-assign device roles (a Cisco router monitors differently than a Dell server).
Visualize connections — critical since a failed switch takes down everything connected to it.
Watch the "big 5" on every device: ping availability, CPU, memory, disk, interface utilization.
Notify via email/text/log when thresholds cross — with a time element (e.g. CPU >80% for 10+ min) to avoid noise from brief spikes.
Real-time and historical dashboards validate designs, expose trends, and isolate problems fast.
An automated messaging system built into network devices — logs notable events (config changes, errors, threshold crossings) and forwards them to admins, feeding the Alert function.
// Key monitoring tools
// Quiz yourself · Unit 11
// Appendix A · Block 1 acronym reference