Table of Contents

Learn the fundamental concepts that form the foundation of modern networking.

Core Concepts

TCP/IP Stack

The TCP/IP stack is the practical implementation of networking protocols used on the internet and is organized into four layers:

  1. Link Layer - Physical and logical connection between devices

    • Examples: Ethernet, Wi-Fi, PPP
    • Handles: MAC addressing, frame formatting

  2. Internet Layer - Addressing, routing, and packaging data

    • Examples: IP, ICMP, ARP
    • Handles: IP addressing, routing, fragmentation

  3. Transport Layer - End-to-end communication services

    • Examples: TCP, UDP
    • Handles: Port numbers, flow control, reliability

  4. Application Layer - Process-to-process data communications

    • Examples: HTTP, FTP, SMTP, DNS
    • Handles: Application-specific protocols

IP Addressing

IPv4 Addressing

  • Format: Four octets (0-255) separated by dots
  • Example: 192.168.1.100
  • Private Ranges:
    • 10.0.0.0/8 (Class A) - 16,777,216 addresses
    • 172.16.0.0/12 (Class B) - 1,048,576 addresses
    • 192.168.0.0/16 (Class C) - 65,536 addresses

IPv6 Addressing

  • Format: Eight groups of four hexadecimal digits
  • Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
  • Simplified: 2001:db8:85a3::8a2e:370:7334

Subnetting

CIDR Subnet Mask Hosts Use Case
/24 255.255.255.0 254 Small office
/23 255.255.254.0 510 Medium office
/22 255.255.252.0 1,022 Large office
/16 255.255.0.0 65,534 Enterprise

Common Protocols

Protocol Layer Port Purpose
HTTP Application 80 Web traffic
HTTPS Application 443 Secure web traffic
FTP Application 20,21 File transfer
SFTP Application 22 Secure file transfer
DNS Application 53 Name resolution
DHCP Application 67,68 IP address assignment
SMTP Application 25 Email sending
SSH Application 22 Secure remote access
RDP Application 3389 Remote desktop
TCP Transport - Reliable connection
UDP Transport - Fast connectionless
ICMP Network - Diagnostics (ping)

Basic Troubleshooting

Common Commands

# Test connectivity
ping 192.168.1.1

# Trace route
traceroute google.com  # Linux/Mac
tracert google.com     # Windows

# Check DNS resolution
nslookup google.com
dig google.com         # Linux/Mac

# Display network configuration
ip addr show           # Linux
ipconfig /all          # Windows

# Show routing table
ip route show          # Linux
route print            # Windows
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