Network Fundamentals

Table of Contents 1. Overview 2. OSI Model 3. IP Addressing 4. Subnetting Basics 5. Routing Essentials 6. Network Security 7. Further Reading

1. Overview

The foundation of modern communication relies on networking. This article introduces core concepts, terminology, and best practices for designing, implementing, and troubleshooting computer networks.

2. OSI Model

The OSI (Open Systems Interconnection) model divides network functions into seven layers:

1. Physical
2. Data Link
3. Network
4. Transport
5. Session
6. Presentation
7. Application

3. IP Addressing

IP addresses uniquely identify devices on a network. IPv4 uses 32‑bit addresses (e.g., 192.168.1.10), while IPv6 uses 128‑bit addresses (e.g., 2001:db8::1).

4. Subnetting Basics

Subnetting divides a larger network into smaller, manageable segments.

# Example: Subnetting a /24 network into four /26 subnets
Network: 192.168.1.0/24
Subnet 1: 192.168.1.0/26  (hosts 1‑62)
Subnet 2: 192.168.1.64/26 (hosts 65‑126)
Subnet 3: 192.168.1.128/26 (hosts 129‑190)
Subnet 4: 192.168.1.192/26 (hosts 193‑254)

5. Routing Essentials

Routers forward packets between networks using routing tables. Common routing protocols include OSPF, BGP, and RIP.

6. Network Security

Key security measures:

Firewalls – filter inbound/outbound traffic.
VPNs – encrypt traffic over public networks.
ACLs – define permitted traffic based on IP/port.
IDS/IPS – detect and prevent intrusions.