DNS, IP addresses, and how a browser finds a server

Module Overview

Before you touch a server, you need to understand what the internet is actually doing when someone visits your website.

Most developers have gaps here - they deploy code without understanding the journey it takes from a browser to a server and back. These gaps become expensive when something breaks.

By the end of this module you will:

• Understand how DNS translates a domain name into an IP address
• Know what happens inside every HTTP and HTTPS request
• Choose the right hosting model for your use case
• Compare VPS providers available in South Africa
• Provision your first live VPS

Lesson 1: DNS, IP Addresses, and How a Browser Finds a Server

Every Device Has an Address

Every device connected to the internet has an IP address - a unique numerical identifier.

Example:

196.22.1.45

IPv4 addresses are four groups of numbers from 0 to 255. IPv6 is the newer format with a larger address space, written as eight groups of hexadecimal values.

The Problem DNS Solves

Humans cannot remember IP addresses. Domain names are the solution.

DNS (Domain Name System) is a globally distributed database that maps domain names to IP addresses.

academyai.co.za  >  196.22.1.45

The DNS Resolution Journey

When you type a domain into your browser:

1. Browser checks its local DNS cache
   > Found? Use it. Done.

2. Browser asks the operating system's DNS resolver
   → Found in OS cache? Use it. Done.

3. OS queries the configured DNS server (usually your router or ISP)
   >  Found? Return it. Done.

4. If not cached, a full recursive lookup begins:

   a. Query a Root Name Server
      >  Returns the address of the .co.za TLD name server

   b. Query the .co.za TLD name server
      >  Returns the address of the domain's authoritative name server

   c. Query the authoritative name server (your DNS host, e.g. Cloudflare)
      >  Returns the A record: the actual IP address

5. Browser connects to the IP address

The entire process typically completes in under 100 milliseconds.

TTL - Time to Live

Every DNS record has a TTL value in seconds. This is how long resolvers cache the record before re-querying.

`academyai.co.za `   A    196.22.1.45    TTL: 3600

A TTL of 3600 means DNS changes take up to one hour to propagate globally. Lower it to 300 before making DNS changes, then restore it afterwards.

Key DNS Terms