Networking Basics for Hackers

Networking Basics for Hackers

March 10, 2025 1 min read Cyber Notes, Networking
#networking #tcp-ip #osi #dns #subnetting

The OSI Model

Layer Name Protocol Examples
7 Application HTTP, DNS, FTP
4 Transport TCP, UDP
3 Network IP, ICMP
2 Data Link Ethernet, ARP
1 Physical Cables, Wi-Fi

TCP vs UDP

  • TCP: Reliable, connection-oriented (3-way handshake: SYN → SYN-ACK → ACK)
  • UDP: Fast, connectionless (used in DNS queries, streaming)

IP Addressing & Subnetting

192.168.1.0/24 = 256 addresses (254 usable)
10.0.0.0/8    = Class A private range
172.16.0.0/12 = Class B private range

Key Tools

  • nmap — Network scanner and port mapper
  • Wireshark — Packet capture and analysis
  • tcpdump — CLI packet capture
  • traceroute / tracert — Path tracing

DNS

nslookup domain.com
dig domain.com ANY

Understanding DNS is critical for reconnaissance in penetration testing.