Quick Study Note — Networking Basics
Concise 2-page summary for quick revision. Good for uploading to StudyLib.
1. OSI and TCP/IP Models (quick)
OSI (7 layers): Application, Presentation, Session, Transport, Network, Data Link, Physical.
TCP/IP (4 layers): Application, Transport, Internet, Link. TCP is reliable (connection-oriented); UDP is
connectionless (faster).
2. Common Protocols
HTTP/HTTPS: Web traffic. HTTPS uses TLS for encryption.
DNS: Domain Name System — resolves names to IPs.
DHCP: Dynamic Host Configuration Protocol — assigns IP addresses.
SSH: Secure remote shell.
3. IP Addressing & Subnetting (essentials)
• IPv4: 32-bit (e.g., 192.168.1.10). IPv6: 128-bit (hexadecimal).
• CIDR notation: e.g., /24 means 255.255.255.0 mask (256 addresses total, 254 usable).
• To find network: bitwise AND IP with subnet mask. Hosts per subnet = 2^(32-mask) - 2 (IPv4 traditional).
4. Routing & Switching (high level)
• Switch: operates at Data Link (MAC addresses), used to connect devices in same LAN.
• Router: operates at Network layer (IP routing between networks).
• Gateway: device that routes between different protocols/networks.
5. Common Commands (Linux/Windows)
ping — check reachability; traceroute / tracert — path to destination; ip a / ifconfig — show interfaces;
netstat — network connections; nslookup / dig — DNS queries.
6. Security Basics
• Use strong encryption (TLS/SSH). Implement firewalls to control traffic. Use VLANs to segment
networks. Keep firmware and OS patched.
7. Quick Study Tips
• Memorize OSI layer order and common protocols per layer. Practice subnetting problems with /24, /25,
/26 masks. Familiarize with basic CLI network commands.
Cheat-sheet: OSI mnemonic — 'All People Seem To Need Data Processing' (Application →
Physical).
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