Networking Basics I Wish I Knew Sooner
You can’t secure what you don’t understand. When I started in cybersecurity, I realized I had huge gaps in my networking knowledge. I could configure a router, but I didn’t truly understand how data flows through networks. This post breaks down the networking fundamentals that every cybersecurity professional needs to know.
The OSI Model (Simplified)
The OSI model is like a blueprint for how data travels across networks. Here’s how I think about it:
📋 The 7 Layers (Top to Bottom)
- Application - HTTP, HTTPS, FTP
- Presentation - Encryption, Compression
- Session - Session Management
- Transport - TCP, UDP
- Network - IP, Routing
- Data Link - Ethernet, MAC
- Physical - Cables, Wireless
TCP vs UDP
Understanding the difference between TCP and UDP is crucial for security analysis:
🔄 TCP (Transmission Control Protocol)
- Connection-oriented
- Reliable delivery
- Error checking
- Flow control
- Used by: HTTP, HTTPS, SSH
⚡ UDP (User Datagram Protocol)
- Connectionless
- Fast delivery
- No error checking
- No flow control
- Used by: DNS, DHCP, Streaming
IP Addressing Made Simple
IP addresses are like phone numbers for computers. Here’s what you need to know:
🌐 IPv4 Addresses
Format: 192.168.1.100 (4 numbers, 0-255 each)
Private Ranges:
- 10.0.0.0 - 10.255.255.255
- 172.16.0.0 - 172.31.255.255
- 192.168.0.0 - 192.168.255.255
Subnet Masks: /24 = 255.255.255.0 (256 addresses)
Common Ports You Should Know
Ports are like apartment numbers in a building (IP address). Here are the most important ones:
Web Traffic
- 80 - HTTP
- 443 - HTTPS
- 8080 - HTTP Alt
System Services
- 22 - SSH
- 23 - Telnet
- 53 - DNS
- 67/68 - DHCP
- 25 - SMTP
- 110 - POP3
- 143 - IMAP
- 993 - IMAPS
DNS: The Internet’s Phone Book
DNS (Domain Name System) converts human-readable names to IP addresses:
- Query: You type “google.com”
- DNS Lookup: Your computer asks DNS server for IP
- Response: DNS returns “142.250.191.14”
- Connection: Your computer connects to that IP
Network Security Implications
Understanding networking helps you understand attacks:
🚨 Common Attack Vectors
- Port Scanning: Checking which ports are open
- DNS Spoofing: Redirecting DNS queries to malicious servers
- Man-in-the-Middle: Intercepting traffic between two parties
- ARP Poisoning: Corrupting ARP tables to redirect traffic
- DDoS: Overwhelming services with traffic
Tools That Help
These tools helped me understand networking better:
- Wireshark: See actual network traffic
- nmap: Scan networks and discover services
- ping/traceroute: Test connectivity and routing
- netstat: See active connections on your machine
- tcpdump: Command-line packet capture
Practical Exercise
Try this simple exercise to see networking in action:
🔬 Hands-On Lab
- Open Wireshark and start capturing
- Open a web browser and visit a website
- Stop the capture and look at the packets
- Find the DNS query and HTTP request
- Notice the TCP handshake (SYN, SYN-ACK, ACK)
Why This Matters for Security
You can’t effectively secure a network if you don’t understand how it works. Knowing networking fundamentals helps you:
- Identify suspicious traffic patterns
- Understand how attacks work
- Configure firewalls and security tools
- Investigate security incidents
- Design secure network architectures
💡 Key Takeaway
Don’t try to memorize everything at once. Start with the basics—TCP/IP, common ports, and DNS. Build your understanding gradually through hands-on practice. The goal isn’t to become a network engineer, but to understand enough to be an effective security professional.