CompTIA A+ Core 1 (220-1201) Cheat Sheet
High-yield review of hardware, ports, Wi-Fi, storage, printers, and troubleshooting patterns for CompTIA A+ Core 1.
On this page
Use this for last-mile review. Core 1 rewards technicians who stay calm, verify the physical and compatibility basics first, and then choose the right tool or component path.
Final 20-minute recall (exam day)
Cue -> best move (scenario map)
| If the question says… | Usually best answer |
|---|---|
169.254.x.x address | DHCP failure path: scope, relay, VLAN, server reachability |
| Names fail but IP works | DNS issue (ipconfig /all, nslookup) |
| Printer smudges/ghosting | Fuser/imaging path issue (laser maintenance parts) |
| Smartphone battery drains fast | Background apps, radios, brightness, health/age check |
| New NVMe not detected | Check M.2 keying/lane support, BIOS/UEFI mode, reseat |
| Slow Wi-Fi in crowded area | 5 GHz or 6 GHz, channel planning, WPA2/3, disable WPS |
| Intermittent network drops | Duplex/speed mismatch, bad cable/connector, duplicate IP |
| “Best redundancy + performance” storage | RAID 10 |
| Need secure remote admin | SSH (not Telnet/RDP exposed broadly) |
| Multiple symptoms after one change | Roll back and apply one-change-at-a-time method |
Must-memorize Core 1 anchors
| Topic | Fast recall |
|---|---|
| Private IPv4 | 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 |
| APIPA | 169.254.0.0/16 (local-only, DHCP miss) |
| Port pairs | DNS 53, DHCP 67/68, RDP 3389, SSH 22, HTTPS 443 |
| Wi-Fi security order | WPA3 -> WPA2 (AES/CCMP) -> WPA (TKIP) -> WEP |
| RAID shorthand | 0 speed, 1 mirror, 5 parity, 10 mirror+stripe |
| Printer process | Processing -> Charging -> Exposing -> Developing -> Transferring -> Fusing -> Cleaning |
Last-minute traps
- Choosing a disruptive fix before basic physical checks (power, cable, link, settings).
- Treating snapshots as backups.
- Leaving WPS/default credentials enabled on SOHO devices.
- Mixing connector standards (M.2 SATA vs NVMe PCIe assumptions).
1) Ports & Protocols (memorize)
| Service | Port/Proto | Notes |
|---|---|---|
| HTTP / HTTPS | 80 TCP / 443 TCP | Web; HTTPS uses TLS |
| SSH | 22 TCP | Secure shell / SFTP |
| FTP / FTPS / SFTP | 20–21 TCP / 990 TCP / 22 TCP | Legacy vs TLS vs SSH |
| SMTP / Submission | 25 / 587 TCP | Outbound email |
| POP3 / IMAP4 (+TLS) | 110 / 143 (995 / 993) TCP | Mail retrieval |
| RDP | 3389 TCP/UDP | Remote desktop |
| DNS | 53 UDP/TCP | Name resolution |
| DHCP | 67/68 UDP | Server/client |
| SNMP | 161/162 UDP | Monitor / traps |
| LDAP / LDAPS | 389 / 636 TCP | Directory |
2) Ethernet Cabling & Standards
| Std | Speed | Max Dist | Cable |
|---|---|---|---|
| 100BASE-TX | 100 Mbps | 100 m | Cat5/5e |
| 1000BASE-T | 1 Gbps | 100 m | Cat5e/6 |
| 10GBASE-T | 10 Gbps | 55 m (Cat6) / 100 m (Cat6a) | Cat6/6a |
3) Fiber & Transceivers
| Type | Mode | Connector | Range |
|---|---|---|---|
| MMF | Multi-mode | LC/SC | Short (LED/VCSEL) |
| SMF | Single-mode | LC/SC | Long (laser) |
Notes: SFP/SFP+ modules match fiber type; clean ends; avoid tight bends.
4) Peripheral & Storage Connectors
- USB: 2.0 (480 Mbps), 3.2 Gen1 (5 Gbps), Gen2 (10), Gen2x2 (20). USB-C supports alt-modes (DP/Thunderbolt).
- Display: HDMI • DisplayPort (DP++) • DVI-D/I • VGA (legacy).
- Storage: SATA (data 7-pin, power 15-pin), M.2 keys (B/M), NVMe over PCIe.
- Thunderbolt 3/4: USB-C, up to 40 Gbps.
5) Wi-Fi Standards
| Std | Bands | Max PHY (theoretical) | Notes |
|---|---|---|---|
| 802.11n (Wi-Fi 4) | 2.4/5 | ~600 Mbps | MIMO |
| 802.11ac (Wi-Fi 5) | 5 | ~6.9 Gbps | MU-MIMO, wide channels |
| 802.11ax (Wi-Fi 6/6E) | 2.4/5/(6E) | >9 Gbps | OFDMA, dense env. |
6) Wi-Fi Security & SOHO Hygiene
- Security order (best→worst): WPA3 → WPA2 (AES/CCMP) → WPA (TKIP) → WEP (avoid).
- SOHO basics: change defaults, WPA2/3-Personal, strong passphrase, firmware updates, disable WPS.
7) IPv4, DHCP & DNS Essentials
- Private ranges: 10.0.0.0/8 • 172.16.0.0–172.31.255.255 (/12) • 192.168.0.0/16
- APIPA: 169.254.0.0/16 → DHCP failure (local-only).
- Quick tells: Names fail but IP works → DNS issue; duplicate IP → intermittent drops.
8) Network Triage (first moves)
- APIPA: Check DHCP scope/reachability/relay, VLAN, gateway/DNS.
- No network: Verify link light, NIC enablement, cabling/port.
- Wi-Fi slow: Prefer 5/6 GHz, right channel width, reduce interference; disable WPS.
9) RAID Levels
| RAID | Disks | Benefit | Notes |
|---|---|---|---|
| 0 | 2+ | Performance | No redundancy |
| 1 | 2 | Redundancy | 50% capacity |
| 5 | 3+ | Redundancy + perf | 1 disk fault tolerant |
| 10 | 4+ | Redundancy + perf | Mirrored stripes |
10) Filesystems & Storage Health
- FS: NTFS (permissions, quotas, EFS), exFAT (flash), FAT32 (legacy).
- SMART warnings: Back up, replace drive.
- M.2/NVMe: Seat fully; confirm BIOS/UEFI detection; check boot order.
11) Printers — Laser Process & Fixes
Order: Processing → Charging → Exposing → Developing → Transferring → Fusing → Cleaning
| Symptom | Likely Cause | First Step |
|---|---|---|
| Streaks/lines | Drum/toner/fuser residue | Clean/replace unit |
| Ghosting | Drum/fuser not discharging | Replace drum/fuser |
| Jams | Rollers/path/humidity | Clear path; clean rollers |
| Faint/uneven | Low toner/transfer | Replace toner; check transfer roller |
12) Displays & Graphics
| Symptom | Cause | Quick Action |
|---|---|---|
| No signal | Loose cable / GPU not seated | Reseat cables/GPU; check input |
| Artifacts/tearing | Driver or cable | Update driver; swap cable/port |
| Dim image | Backlight/power | Adjust brightness; test external |
| Color shift | Profile/cable | Reset profile; try HDMI/DP |
13) Mobile Devices
- Connectivity: Tethering vs hotspot; Wi-Fi calling.
- Accessories: NFC, Bluetooth profiles (A2DP/HFP).
- Triage: Safe mode (Android), DFU/Recovery (iOS), clear app cache/data, battery health.
14) Virtualization & Client Cloud
- Type 1 vs Type 2 hypervisors (bare-metal vs hosted).
- VM resources: vCPU, memory ballooning, vNICs.
- Snapshots ≠ backups (short-term only).
- Cloud use: Storage sync (OneDrive/Drive), thin clients, basic VDI awareness.
15) Windows CLI & Tools
| Need | Tool/Command | Use |
|---|---|---|
| IP stack | ipconfig /all | DHCP/DNS/gateway check |
| Reachability | ping, tracert | Latency, path issues |
| Name resolution | nslookup | DNS testing |
| Shares | net use | Map drives; creds |
| Disk | chkdsk, diskpart, defrag | Filesystem/partition |
| System health | sfc /scannow, DISM /Online /Cleanup-Image /RestoreHealth | Image repair |
| Logs | Event Viewer | System/Application issues |
16) ESD/Safety & Troubleshooting Method
ESD & safety: Strap to ground, antistatic mat, handle by edges, ESD bags; surge/UPS; toner cleanup with cold water/ESD-safe vac.
Method (always show this logic):
- Identify the problem (gather, duplicate, what changed).
- Establish a probable cause (theory).
- Test the theory → confirm root cause.
- Plan and implement the fix.
- Verify full functionality; implement prevention.
- Document findings/actions/outcomes.
Golden rules: Start least intrusive, change one thing at a time, preserve data and user impact awareness.
Quiz
Loading quiz…
From here, go to the FAQ for deeper scenario explanations or use the resources page for official exam details and safe lab references.