CompTIA A+ / Network+ / Security+ CompTIA A+ Core 1: Hardware, Mobile Devices & Networking (220-1101) Syllabus

List the Wi-Fi standards 802.11a/b/g/n/ac/ax with their frequency bands and approximate maximum throughput.

802.11a: $5\ \text{GHz}$, up to $54\ \text{Mbps}$. 802.11b: $2.4\ \text{GHz}$, up to $11\ \text{Mbps}$. 802.11g: $2.4\ \text{GHz}$, up to $54\ \text{Mbps}$. 802.11n (Wi-Fi 4): $2.4/5\ \text{GHz}$, up to $600\ \text{Mbps}$. 802.11ac (Wi-Fi 5): $5\ \text{GHz}$, up to several $\text{Gbps}$. 802.11ax (Wi-Fi 6/6E): $2.4/5/6\ \text{GHz}$, highest efficiency and throughput.

Compare the 2.4 GHz and 5 GHz Wi-Fi bands in terms of range, speed, and interference.

$2.4\ \text{GHz}$ has longer range and better wall penetration but lower speed and more congestion/interference (fewer non-overlapping channels: 1, 6, 11). $5\ \text{GHz}$ offers higher speed and many more non-overlapping channels with less interference, but shorter range and weaker penetration.

What technology, introduced with 802.11n and enhanced in ac/ax, uses multiple antennas to improve throughput, and what does MU-MIMO add?

MIMO (Multiple Input Multiple Output) uses multiple antennas/spatial streams to increase throughput and reliability. MU-MIMO (Multi-User MIMO) lets the AP communicate with several clients simultaneously rather than one at a time, improving efficiency on busy networks.

Define DHCP scope, lease, reservation, and exclusion.

Scope = the pool/range of IP addresses a DHCP server can assign. Lease = the time period a client may use an assigned address before renewal. Reservation = a specific IP permanently tied to a device's MAC address. Exclusion = address(es) within the scope the server will not hand out (e.g., for static devices).

What is the purpose of DNS, and what do A, AAAA, MX, and CNAME records do?

DNS resolves human-readable domain names to IP addresses. A record maps a name to an IPv4 address; AAAA maps to an IPv6 address; MX specifies the mail server for a domain; CNAME is an alias pointing one name to another canonical name.

Explain a VLAN and one key benefit it provides.

A VLAN (Virtual LAN) logically segments a physical switch into separate broadcast domains. Benefits include improved security (isolating traffic between groups), reduced broadcast traffic, and easier logical grouping of devices regardless of physical location.

What is a VPN and what does it provide?

A VPN (Virtual Private Network) creates an encrypted tunnel over a public network (the internet), allowing a remote user or site to securely access a private network as if locally connected, protecting confidentiality and integrity of the data in transit.

Differentiate between NAT and port forwarding.

NAT (Network Address Translation) lets multiple private IP devices share one public IP for outbound internet access. Port forwarding is a NAT rule that directs inbound traffic on a specific external port to a designated internal host/port, allowing external access to an internal service (e.g., a web server).

Compare common internet connection types: DSL, cable, fibre, and satellite.

DSL runs over telephone lines (moderate speed, distance-limited). Cable uses the coaxial TV network (faster, shared bandwidth). Fibre uses optical cable for the highest speeds and low latency. Satellite covers remote areas but has high latency and weather sensitivity.

Define LAN, WAN, PAN, MAN, and WLAN.

LAN = Local Area Network (single site). WAN = Wide Area Network (geographically large, e.g., the internet). PAN = Personal Area Network (short range, e.g., Bluetooth). MAN = Metropolitan Area Network (city-sized). WLAN = Wireless LAN (Wi-Fi).

Compare twisted-pair categories Cat 5, Cat 5e, Cat 6, and Cat 6a in speed and distance.

Cat 5: up to $100\ \text{Mbps}$. Cat 5e: $1\ \text{Gbps}$ to $100\ \text{m}$. Cat 6: $10\ \text{Gbps}$ up to about $55\ \text{m}$ (1 Gbps to 100 m). Cat 6a: $10\ \text{Gbps}$ to the full $100\ \text{m}$. All have a standard maximum segment length of $100\ \text{m}$ for their rated 1 Gbps use.

Distinguish single-mode from multimode fibre-optic cable.

Single-mode fibre has a very thin core, uses a laser light source, and supports very long distances (kilometres) with minimal attenuation. Multimode fibre has a larger core, uses LED/VCSEL sources, allows multiple light paths, and is used for shorter distances (typically up to a few hundred metres) at lower cost.

Identify the connector types: RJ45, RJ11, BNC, and F-type.

RJ45 = 8-pin connector for twisted-pair Ethernet. RJ11 = smaller 4/6-pin connector for telephone/DSL lines. BNC = bayonet connector for older coaxial (10BASE2) networks. F-type = screw-on coaxial connector used for cable TV/internet (RG-6/RG-59).

Compare T568A and T568B wiring standards and explain when a crossover cable is needed.

T568A and T568B are the two pin-out colour-code standards for terminating RJ45 connectors; they swap the green and orange pairs. A straight-through cable uses the same standard on both ends (host to switch). A crossover cable uses T568A on one end and T568B on the other, historically needed to connect like devices (PC-to-PC, switch-to-switch) before Auto-MDIX.

List the DDR generations DDR2, DDR3, DDR4, and DDR5 with a key distinguishing feature.

DDR2: 240-pin DIMM, ~$1.8\ \text{V}$. DDR3: 240-pin (different notch), ~$1.5\ \text{V}$. DDR4: 288-pin, ~$1.2\ \text{V}$, higher speeds. DDR5: 288-pin, ~$1.1\ \text{V}$, on-module power management and even higher bandwidth. Generations are keyed differently and not interchangeable.

Explain the difference between single-channel, dual-channel, and quad-channel memory.

These describe how many parallel data paths the memory controller uses. Dual-channel doubles the effective memory bandwidth versus single-channel by accessing two modules simultaneously; quad-channel uses four. To enable multi-channel you must install matched modules in the correctly colour-coded/paired slots.

What is ECC RAM and where is it typically used?

ECC (Error-Correcting Code) RAM uses an extra bit to detect and correct single-bit memory errors automatically. It is used in servers and workstations where data integrity is critical; it requires a CPU/motherboard that supports ECC.

Compare HDD, SSD, and NVMe storage in interface and performance.

HDD: mechanical platters, SATA interface, slowest, cheapest per GB. SATA SSD: flash memory over SATA (~$600\ \text{MB/s}$ limit), much faster, no moving parts. NVMe SSD: flash over the PCIe bus (M.2), far higher throughput and lower latency than SATA SSDs.

Compare common HDD form factors and rotational speeds.

Desktop HDDs are $3.5\text{-inch}$; laptops use $2.5\text{-inch}$ drives. Common spindle speeds are $5400\ \text{rpm}$ (cooler, quieter, slower) and $7200\ \text{rpm}$ (faster); enterprise drives reach $10{,}000$ or $15{,}000\ \text{rpm}$. Higher rpm gives faster data access.

Describe the M.2 storage form factor and the difference between SATA and NVMe M.2 keying.

M.2 is a small gumstick-style slot for SSDs. M.2 drives can use the SATA or PCIe/NVMe protocol. Keying notches (B-key, M-key, B+M) indicate which interfaces a module/slot supports: M-key slots support PCIe x4 NVMe, B-key supports SATA/PCIe x2; you must match the drive's protocol to the slot's supported interface.

Define RAID 0, RAID 1, RAID 5, and RAID 10 and their fault tolerance.

RAID 0: striping, no redundancy, best performance, no fault tolerance (min 2 disks). RAID 1: mirroring, survives one disk failure (2 disks). RAID 5: striping with distributed parity, survives one disk failure (min 3 disks). RAID 10: mirrored stripes, high performance and redundancy, survives at least one disk per mirror (min 4 disks).

Compare ATX, microATX, mini-ITX, and ITX motherboard form factors.

ATX is full-size with the most expansion slots and ports. microATX (mATX) is smaller with fewer slots. mini-ITX is a compact $17 \times 17\ \text{cm}$ board with usually one expansion slot for small builds. Smaller form factors trade expandability for size.

Differentiate Intel and AMD CPU sockets and the terms LGA versus PGA.

LGA (Land Grid Array) places the pins in the socket and flat contacts on the CPU—used by Intel (e.g., LGA1700). PGA (Pin Grid Array) places the pins on the CPU and holes in the socket—traditionally used by AMD (e.g., AM4). The CPU must match the motherboard's socket exactly.

Explain CPU features: cores, threads, hyper-threading, and virtualisation support.

Cores are independent processing units. Threads are execution streams; hyper-threading (Intel) / SMT (AMD) lets one core handle two threads to improve throughput. Hardware virtualisation support (Intel VT-x / AMD-V) enables efficient hosting of virtual machines and must be enabled in BIOS/UEFI.

Compare PCIe slot sizes x1, x4, x8, and x16 and their typical uses.

PCIe slot size reflects the number of lanes: x1 (sound/NIC cards), x4 (some NVMe/RAID cards), x8, and x16 (graphics cards). More lanes = more bandwidth. A smaller card fits in a larger slot (up-plugging), and lanes scale with the link width negotiated.

List standard power-supply (PSU) DC output voltages and the main connectors.

A PSU outputs $+3.3\ \text{V}$, $+5\ \text{V}$, and $+12\ \text{V}$ (plus $-12\ \text{V}$). Key connectors: 24-pin main ATX motherboard, 4/8-pin CPU (EPS), 6/8-pin PCIe for GPUs, SATA power, and Molex. The $+12\ \text{V}$ rail powers CPU and GPU.

What two electrical specifications must match a power supply to a region and a system's needs?

Input voltage: the PSU must match mains voltage ($110$–$120\ \text{V}$ in some regions vs $220$–$240\ \text{V}$ in the UK), set by an auto-switching or manual selector. Wattage: the PSU output rating (in watts) must exceed the total power draw of all components, with headroom for stability.

Differentiate inkjet, laser, thermal, and impact printers by their printing mechanism.

Inkjet sprays liquid ink droplets onto paper. Laser uses a laser, charged drum, and toner fused by heat. Thermal uses heat to darken special thermal paper (receipts). Impact (dot-matrix) strikes an inked ribbon against paper through pins—the only common type that can print multipart carbon forms.

List the seven steps of the laser printing (imaging) process in order.

1. Processing, 2. Charging, 3. Exposing, 4. Developing, 5. Transferring, 6. Fusing, 7. Cleaning. (Mnemonic: 'Please Come Every Day To Find Cookies.') The drum is charged, the laser exposes/writes the image, toner is developed onto it, transferred to paper, fused with heat, and the drum is cleaned.

Define the three NIST cloud service models: IaaS, PaaS, and SaaS.

IaaS (Infrastructure as a Service) provides virtual hardware—VMs, storage, networking—that the customer manages. PaaS (Platform as a Service) provides a development/runtime platform so customers deploy apps without managing the OS/hardware. SaaS (Software as a Service) delivers ready-to-use applications over the internet (e.g., webmail).

Compare public, private, hybrid, and community cloud deployment models.

Public cloud is shared infrastructure owned by a provider, available to anyone (multi-tenant). Private cloud is dedicated to a single organisation. Hybrid combines public and private with orchestration between them. Community cloud is shared by several organisations with common requirements.

Define the key cloud characteristics: rapid elasticity, on-demand self-service, resource pooling, and measured service.

Rapid elasticity: resources scale up/down quickly with demand. On-demand self-service: users provision resources automatically without provider intervention. Resource pooling: a multi-tenant model sharing pooled resources. Measured service: usage is metered so you pay only for what you consume.

Distinguish a Type 1 from a Type 2 hypervisor in client-side virtualisation.

A Type 1 (bare-metal) hypervisor runs directly on the hardware with no host OS (e.g., ESXi, Hyper-V), offering better performance for servers. A Type 2 (hosted) hypervisor runs as an application on top of a host OS (e.g., VirtualBox, VMware Workstation), common for desktop/client-side virtualisation.

What are the resource requirements and one purpose of a sandbox in client-side virtualisation?

Each VM needs adequate CPU (with VT-x/AMD-V enabled), RAM, disk space, and network resources allocated from the host. A sandbox is an isolated VM/environment used to safely test software or analyse malware without affecting the host system.

List the six steps of the CompTIA troubleshooting methodology in order.

1. Identify the problem. 2. Establish a theory of probable cause (question the obvious). 3. Test the theory to determine cause. 4. Establish a plan of action and implement the solution. 5. Verify full system functionality and implement preventive measures. 6. Document findings, actions, and outcomes.

In the troubleshooting methodology, what should you always consider during the 'identify the problem' step regarding changes and backups?

Gather information, question the user, identify symptoms, determine if anything recently changed, and—critically—perform backups before making changes. Also inquire about environmental or infrastructure changes so you don't lose data or overlook a recent modification as the cause.

What do common POST beep codes and POST/diagnostic indicators help you diagnose, and what does a single beep usually mean?

POST (Power-On Self-Test) beep codes and on-board LEDs/codes report hardware faults found at boot (RAM, GPU, CPU). The pattern is vendor-specific, but a single short beep typically indicates a successful POST/normal boot. Repeated or patterned beeps usually indicate a memory or video failure.

What are the symptoms and likely causes of failing RAM?

Symptoms: random reboots, frequent BSODs/lock-ups, failure to boot with POST beeps, or memory errors. Causes: faulty or improperly seated modules, incompatible/mismatched RAM. Diagnose by reseating, testing one module at a time, or running a memory diagnostic (e.g., Windows Memory Diagnostic / MemTest).

What symptoms point to a failing or inadequate power supply, and how do you confirm it?

Symptoms: no power at all, intermittent shutdowns/reboots, system powers on then dies, burning smell, or instability under load. Confirm with a PSU tester or multimeter checking the rail voltages ($+3.3$, $+5$, $+12\ \text{V}$), and verify the fan spins. Replace if voltages are out of tolerance.

What does a continuously running/over-spinning fan, or unexpected shutdowns, indicate about a CPU/motherboard, and what causes thermal shutdown?

It indicates overheating. Unexpected shutdowns are often the system's thermal protection cutting power to prevent CPU damage. Causes include failed/clogged fans, dried-out thermal paste, dust buildup, or a failing heat sink. Reapply thermal paste, clean dust, and ensure fans/airflow work.

What are common indicators of an impending hard-drive (storage) failure?

Indicators: read/write errors, slow performance, frequent crashes, clicking or grinding noises (HDD), S.M.A.R.T. warnings, files becoming corrupt or disappearing, and extended/loud boot times. Back up data immediately and run diagnostics; replace the drive.

What does a RAID controller report when an array is degraded, and what is the correct action for a single failed disk in RAID 5?

A degraded array means one disk has failed but data is still accessible via parity/mirroring. For RAID 5 with one failed disk, replace the failed drive promptly and let the array rebuild from parity. Do not delay—a second disk failure before rebuild completes causes total data loss.

What does the message 'RAID not found' or array failing to initialise typically indicate at boot?

It usually indicates a controller, cabling, or multiple-drive failure, an incorrectly configured/missing RAID configuration, or the drives not being detected. Check power and data cables, the controller/BIOS RAID settings, and whether more disks than the array's tolerance have failed.

What are the likely causes of a dim laptop display, flickering, or no image, and how do you isolate them?

Dim screen: failed backlight/inverter or low brightness setting. Flickering: loose display cable, failing inverter, or driver issue. No image: connect an external monitor—if external works, the LCD panel/cable/backlight is faulty; if not, the GPU or board is at fault.

List common mobile device display/touch faults and their typical fixes.

Dim or no display: check brightness, auto-brightness sensor, or replace backlight/screen. Unresponsive/erratic touch: recalibrate, remove screen protector, replace digitiser, or restart. Flickering/artifacts: faulty display or loose connector. Overheating can also cause dimming and shutdowns.

Outline the structured approach to troubleshooting no network connectivity on a workstation.

Check physical link/LED lights and cable first. Verify IP configuration with ipconfig/ifconfig (an APIPA $169.254.x.x$ address means DHCP failed). Test loopback ($127.0.0.1$), then the default gateway, then an external IP, then a DNS name to isolate whether the issue is local, gateway, or DNS.

What does an APIPA address ($169.254.x.x$) on a client indicate?

It indicates the client failed to obtain an address from a DHCP server and self-assigned an Automatic Private IP Address. Causes include an unreachable/offline DHCP server, a bad cable/switch port, or exhausted DHCP scope. The device can only communicate on the local link, not beyond it.

Which command-line tools test latency and trace the path to a remote host, and what does each show?

ping tests reachability and round-trip latency to a host using ICMP. tracert (Windows) / traceroute (Linux) shows each router hop along the path and the latency at each, helping locate where connectivity slows or fails. pathping combines both.

What are the causes and fixes for poor or intermittent wireless connectivity?

Causes: weak signal/distance, interference (other APs, microwaves, $2.4\ \text{GHz}$ congestion), channel overlap, or wrong band. Fixes: move closer or add an AP/repeater, change to a less congested channel (1/6/11) or the $5\ \text{GHz}$ band, update drivers, and check antenna connections.

What are the symptoms and causes of laser printer faults: a repeating spot/mark, smudged toner, and ghost/faded images?

Repeating spots at regular intervals = a defect on the drum or roller. Toner that smudges or rubs off = a failed fuser (not bonding toner). Faded/ghost images = low toner, a worn drum, or fuser/charge issues. Vertical streaks indicate a scratched drum or debris on the corona wire.

What causes paper jams in printers and what are key preventive steps?

Causes: worn/dirty pickup rollers, wrong or damp paper, overfilled tray, debris, or a faulty fuser/feed assembly. Prevention: use the correct paper weight, store paper dry, don't overfill, clean rollers, and ensure the paper path is clear and components (separation pad, rollers) are in good condition.

For an inkjet printer producing lines or gaps in output, what maintenance steps should you perform?

Run the printer's nozzle/head cleaning cycle to clear clogged nozzles, then run a print-head alignment and nozzle-check pattern. Replace empty or dried cartridges. If cleaning fails repeatedly, the print head may need replacement. Use the printer regularly to prevent ink drying.