CompTIA A+ Core 1 (220-1201) Cheatsheet — High-Yield Tables & Quick Rules
Fast recall for 220-1201: hardware, mobile, networking, virtualization/cloud, and troubleshooting. Includes port numbers, cables, Wi-Fi standards, RAID levels, display issues, printer flows, ESD/safety, and tool pickers.
On this page
Use this for last-mile review. Skim top to bottom; star weak rows and re-drill with practice.
1) Common Ports (know by heart)
| Service | Port/Proto | Notes |
|---|---|---|
| HTTP / HTTPS | 80 TCP / 443 TCP | Web browsing; HTTPS = TLS |
| SSH | 22 TCP | Secure remote shell / SFTP |
| FTP | 20/21 TCP | Data/control; legacy, unencrypted |
| SFTP / FTPS | 22 TCP / 990 TCP | SSH vs TLS variants |
| SMTP | 25 TCP | Mail transfer (legacy) |
| SMTPS / Submission | 465 or 587 TCP | Modern sending via TLS |
| POP3 / IMAP4 | 110 / 143 TCP | Mail retrieval |
| POP3S / IMAPS | 995 / 993 TCP | TLS-secured retrieval |
| RDP | 3389 TCP/UDP | Remote desktop |
| DNS | 53 UDP/TCP | Name resolution |
| DHCP | 67/68 UDP | Server/client; leases |
| SNMP | 161/162 UDP | Monitor / traps |
| LDAP / LDAPS | 389 / 636 TCP | Directory services |
2) Cables, Connectors & Speeds
Twisted Pair (Ethernet)
| Standard | Speed | Distance | 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 |
Fiber (typical)
| Type | Mode | Connector | Notes |
|---|---|---|---|
| MMF | Multi-mode | LC/SC | Short range (LED/VCSEL) |
| SMF | Single-mode | LC/SC | Long range (laser) |
PC/Peripherals
- USB: A/C; 2.0 (480 Mbps), 3.x (5/10/20 Gbps), USB-C alt-modes (DP/Thunderbolt).
- Display: HDMI, DisplayPort (DP++), DVI (DVI-I/-D), VGA (legacy).
- Storage: SATA data (7-pin) + power (15-pin), M.2 keys (B/M), NVMe over PCIe.
- Thunderbolt 3/4: USB-C connector; up to 40 Gbps.
3) Wireless & SOHO Networking
Wi-Fi Generations (2.4/5/6 GHz)
| 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, wider channels |
| 802.11ax (Wi-Fi 6/6E) | 2.4/5/(6E) | >9 Gbps | OFDMA, better dense env. |
Security order (best→worst): WPA3 → WPA2 (AES/CCMP) → WPA (TKIP) → WEP (avoid).
SOHO Router basics: Change defaults, WPA2/3-Personal, strong passphrase, firmware updates, disable WPS.
4) IP, DHCP, and Basics
- Private IPv4 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 (no DHCP lease; local only).
- Common symptoms:
- APIPA address → DHCP/reachability issue (check cable/switch/router).
- Duplicate IP → Random disconnects; clear static conflicts or reservations.
- DNS wrong → Names fail but pings by IP work.
5) Storage, RAID & Filesystems
| RAID | Disks | Benefit | Notes |
|---|---|---|---|
| 0 (Stripe) | 2+ | Performance | No redundancy |
| 1 (Mirror) | 2 | Redundancy | Halves capacity |
| 5 (Stripe+Parity) | 3+ | Redundancy + perf | One disk can fail |
| 10 (1+0) | 4+ | Redundancy + perf | Mirrored stripes |
Filesystems: NTFS (permissions, EFS, quotas), exFAT (flash), FAT32 (legacy).
SMART warnings → back up, replace drive.
6) Displays & Graphics (Fast Fixes)
| Symptom | Likely Cause | Quick Action |
|---|---|---|
| No signal / POST beep | Loose cable, GPU not seated | Reseat GPU/cables; check input |
| Dim image | Power saving / backlight | Toggle brightness/power; test with external |
| Artifacts/tearing | Driver or cable | Update driver; swap cable/port; vsync |
| Color shift | Profile/cable | Reset profile; test HDMI/DP |
7) Printers (Laser focus + common flows)
Laser steps (order): Processing → Charging → Exposing → Developing → Transferring → Fusing → Cleaning.
Common issues:
- Streaks/lines → Drum/toner issue, fuser cleaning.
- Ghosting → Fuser/drum not discharging; replace unit.
- Paper jams → Path rollers, humidity; use proper media; clean rollers.
- Wireless fail → Re-add via IP; check subnet, DHCP reservation.
8) Mobile Devices
- iOS/Android: Screen types (OLED vs LCD), tethering vs hotspot, MDM basics.
- Accessories: NFC (payments), Bluetooth profiles (A2DP/HFP), Wi-Fi calling.
- Troubleshooting: Safe mode (Android), DFU/Recovery (iOS), app cache/data reset, battery health.
9) Virtualization & Cloud (Core 1 depth)
- Type 1 vs Type 2 hypervisors (bare-metal vs hosted).
- VM resources: CPU, memory ballooning, virtual NICs, snapshots (not backups).
- Cloud models: IaaS/PaaS/SaaS conceptually; elasticity vs scalability.
- Client cloud use: Storage sync (OneDrive/Drive), thin clients, VDI basics.
10) Command-Line & Tools (Windows focus)
| Need | Tool/Command | Notes |
|---|---|---|
| IP config | ipconfig /all | Check DHCP/DNS/gateway |
| DNS test | nslookup / ping | Name vs IP reachability |
| Routes | tracert | Path latency / hop failures |
| Shares | net use | Map drives; check creds |
| Disk | chkdsk, diskpart, defrag | File/partition health |
| System | sfc /scannow, DISM /restorehealth | Repair images |
| Logs | Event Viewer | System/Application logs |
11) ESD, Safety & Environment
- ESD control: Wrist strap to ground, antistatic mat, handle by edges, store in bags.
- Power: Use surge protectors/UPS for critical devices.
- MSDS/SDS awareness; toner cleanup with cold water and no vacuum (unless ESD-safe).
- Lifting/cables: Proper posture; cable management to avoid hazards.
12) Troubleshooting Method (always show this thinking)
- Identify the problem (gather, duplicate, ask what changed).
- Establish probable cause (theory).
- Test the theory → confirm root cause.
- Establish plan of action and fix.
- Verify full system functionality; implement prevention.
- Document findings/actions/outcomes.
Golden rules
- Change one thing at a time; start with the least intrusive step.
- Reproduce the issue consistently before declaring fixed.
- Always think user impact and data preservation first.
13) Quick Pickers
- No network but link light on: IP/DHCP/DNS stack before cabling.
- APIPA address: DHCP scope/reachability (check relay, VLAN, router).
- Random reboots: Thermals, PSU, RAM seating; check event logs.
- Slow file copies on Wi-Fi: 2.4 GHz congestion → move to 5/6 GHz; channel width.
- Laptop hot / throttling: Clean vents, repaste, power plan, background apps.
14) Mini-Glossary
Throughput vs Bandwidth (actual vs theoretical) • Latency (delay) • PoE (power over Ethernet) • NAT (private↔public translation) • QoS (priority) • Duplex (full/half) • UEFI (modern firmware) • PXE (network boot) • VLAN (segmentation).
How to use: If you hesitate on a row, add it to tomorrow’s drill list and re-test with a 15–20 question set focusing that area.