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.
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Use this for last-mile review. Star weak rows and re-drill with practice.
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 | Charge -> Expose -> Develop -> Transfer -> Fuse -> Clean |
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 /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
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From here, go to the FAQ for deeper scenario explanations or use the resources page for official exam details and safe lab references.