Quick Reference Sheet

The essentials from Getting Started in IT, organized by cert. This is the free slice — the platform's Condensed Study Guide goes chapter-by-chapter with the full Real World Priority ratings.

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Troubleshooting Methodology (CompTIA's 6 Steps)

#	Step
1	Identify the problem
2	Establish a theory of probable cause
3	Test the theory to determine cause
4	Establish a plan of action, then implement it
5	Verify full system functionality, implement preventive measures
6	Document findings, actions, and outcomes

Exam Trap: The exam presents scenarios out of order and asks "what's the NEXT step" — memorize the order, not just the steps.

RAM Types

DDR3 — 240-pin, older desktops DDR4 — 288-pin, most common current desktop/laptop RAM DDR5 — newest standard, higher bandwidth SODIMM — laptop form factor (any DDR generation)

Storage & Connectors

Type	Notes
HDD	Spinning platter, SATA connector, slowest, cheapest per GB
SATA SSD	Same SATA connector as HDD, much faster, no moving parts
NVMe SSD	M.2 slot, uses PCIe lanes directly, fastest consumer option
USB-C	Reversible connector; speed depends on the standard behind it — the shape alone tells you nothing about speed

Exam Trap: M.2 is a slot/form factor, not a speed. An M.2 drive can be SATA or NVMe — don't assume M.2 always means fast.

Windows Command Line Essentials

Command	Does
ipconfig /all	Full network config
ipconfig /flushdns	Clear DNS cache
ping	Test reachability
tracert	Trace hop path

Command	Does
sfc /scannow	Repair system files
chkdsk	Check disk for errors
gpupdate /force	Force policy refresh
netstat -an	Active connections/ports

Mobile Device Connectivity

Bluetooth — short range, peripherals NFC — inches, tap-to-pay Wi-Fi Direct — device to device, no router Cellular (LTE/5G) — carrier data

Real World: Rated a 3 in the book — you won't be swapping RAM types daily, but knowing what a client actually has before you order parts saves a return-shipping headache every single time.

The OSI Model

7ApplicationHTTP, DNS, SMTP — user-facing protocols

6PresentationEncryption, encoding, compression (TLS lives here)

5SessionOpens/manages/closes a connection

4TransportTCP (reliable) vs UDP (fast) — ports live here

3NetworkIP addressing and routing — packets

2Data LinkMAC addresses, switches, frames

1PhysicalCables, signals, NICs — actual bits

Memory trick: "Please Do Not Throw Sausage Pizza Away" — top to bottom, Physical → Application.

Ports You'll Actually Be Tested On

Port	Protocol
20/21	FTP (data/control)
22	SSH
23	Telnet
25	SMTP
53	DNS
67/68	DHCP
69	TFTP
80	HTTP

Port	Protocol
110	POP3
143	IMAP
161/162	SNMP
389	LDAP
443	HTTPS
445	SMB
3389	RDP
8080	HTTP (alt)

Exam Trap: HTTPS is 443, not 80 — near-identical pairs like this are the exam's favorite trick.

Subnet Cheat Table

CIDR	Mask	Usable Hosts
/24	255.255.255.0	254
/25	255.255.255.128	126
/26	255.255.255.192	62
/27	255.255.255.224	30
/28	255.255.255.240	14
/29	255.255.255.248	6
/30	255.255.255.252	2

Real World: Rated a 2 — subnet calculators exist for a reason. Know the math well enough to verify a calculator, not necessarily hand-calculate a /27 at 2am.

Private IP Ranges

Class	Range	Default Mask
A	10.0.0.0 – 10.255.255.255	255.0.0.0
B	172.16.0.0 – 172.31.255.255	255.255.0.0
C	192.168.0.0 – 192.168.255.255	255.255.255.0

Wireless Standards

Standard	Band	Notes
802.11n	2.4/5 GHz	Wi-Fi 4
802.11ac	5 GHz	Wi-Fi 5
802.11ax	2.4/5/6 GHz	Wi-Fi 6 / 6E

Exam Trap: Rated a 1 in the book — exam-only knowledge. Memorize the table, don't lose sleep over it.

Connectivity Troubleshooting Tools

Cable tester — verify wiring continuity Toner probe — trace a cable through a wall Loopback plug — test a port in isolation Punch-down tool — terminate cable into a jack/patch panel

The CIA Triad

Principle	Means
Confidentiality	Only authorized people can see the data
Integrity	Data hasn't been altered, tampered, or corrupted
Availability	Systems and data are accessible when needed

Exam Trap: Every scenario question maps back to one of these three. If you're stuck, ask "which one of the three is actually being violated here?"

AAA Framework

Authentication — proving who you are Authorization — what you're allowed to do Accounting — logging what you actually did

Common Attack Types

Attack	What it is
Phishing	Deceptive email/message to trick a user into acting
Spear phishing	Phishing targeted at a specific person
Whaling	Phishing targeted at an executive
Man-in-the-middle	Attacker intercepts traffic between two parties
DDoS	Overwhelm a system with traffic from many sources
Ransomware	Encrypts data, demands payment to restore it
SQL injection	Malicious SQL inserted through an input field
Brute force	Trying every possible password combination

Real World: Ransomware defense is rated a 4 — you will deal with this, or at minimum prepare for it, at some point in your career. This is not exam-only knowledge.

Encryption Basics

Type	Key behavior
Symmetric	One shared key, both encrypt and decrypt. Fast (e.g., AES).
Asymmetric	Public/private key pair. Slower, used for exchange/signing (e.g., RSA).
Hashing	One-way — not encryption. Verifies integrity (e.g., SHA-256).

Exam Trap: Hashing isn't encryption — you can't "decrypt" a hash. It's a one-way fingerprint used to verify nothing changed.

Security Controls by Type

Preventive — firewalls, MFA Detective — IDS, logging Corrective — backups, patching Deterrent — warning banners, cameras Compensating — a workaround when the ideal control isn't feasible

Incident Response Steps

#	Phase
1	Preparation
2	Identification
3	Containment
4	Eradication
5	Recovery
6	Lessons learned

Real World: Patch management and BitLocker are both rated 4s in the book. These aren't theoretical — they're what actually keeps you off the front page after a breach.

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