Overview - IP addresses (IPv4, IPv6)

What is it?

An IP address is a unique number assigned to every device connected to the internet or a local network. It acts like a home address, telling other devices where to send information. There are two main types: IPv4, which uses four sets of numbers, and IPv6, which uses a longer format with letters and numbers. These addresses help devices find and communicate with each other.

Why it matters

Without IP addresses, devices on the internet would not know where to send data, making online communication impossible. Imagine trying to send a letter without a home address; it would never reach the right place. IP addresses solve this by giving every device a unique location, enabling websites, emails, and apps to work smoothly.

Where it fits

Before learning about IP addresses, you should understand basic networking concepts like devices and data transfer. After this, you can explore topics like DNS (which translates IP addresses to names) and routing (how data travels across networks). IP addresses are a foundational step in understanding how the internet works.

Mental Model

Core Idea

An IP address is a unique digital home address that lets devices find and talk to each other on a network.

Think of it like...

Think of an IP address like a postal address for your house. Just as mail carriers need your home address to deliver letters, computers need IP addresses to send data to the right device.

┌───────────────┐       ┌───────────────┐       ┌───────────────┐
│ Device A      │──────▶│ Router/ISP    │──────▶│ Device B      │
│ IP: 192.168.1.2│      │ IP: 203.0.113.1│      │ IP: 192.168.1.3│
└───────────────┘       └───────────────┘       └───────────────┘

Data flows from Device A to Device B using their IP addresses to find each other.

Build-Up - 7 Steps

1

FoundationWhat is an IP Address?

Concept: Introduce the basic idea of an IP address as a unique identifier for devices on a network.

Every device connected to a network needs a unique number called an IP address. This number helps devices send and receive information correctly. Think of it as a name tag that computers wear so they can find each other.

Result

You understand that an IP address is like a device's unique name on a network.

Knowing that devices need unique identifiers is the first step to understanding how networks organize communication.

2

FoundationIPv4 Address Format Basics

3

IntermediateWhy IPv6 Was Created

4

IntermediateIPv6 Address Format Explained

5

IntermediatePublic vs Private IP Addresses

6

AdvancedHow IP Addresses Enable Routing

7

ExpertIPv6 Address Compression and Notation

Under the Hood

IP addresses work by labeling devices with unique numbers so that data packets can be sent from one device to another. When a device sends data, it includes the destination IP address in the packet header. Routers along the path read this address and forward the packet closer to its destination. IPv4 uses 32 bits for addresses, limiting the number of unique addresses, while IPv6 uses 128 bits, vastly increasing the address space. Internally, devices and routers use binary representations of these addresses to perform fast lookups and routing decisions.

Why designed this way?

IPv4 was designed in the early days of the internet when fewer devices existed, so 32-bit addresses seemed sufficient. As the internet grew, the shortage of IPv4 addresses became a problem, leading to the design of IPv6 with 128-bit addresses to future-proof the system. The design balances uniqueness, routing efficiency, and backward compatibility. The use of hexadecimal in IPv6 makes the long addresses more readable for humans.

┌───────────────┐
│ Device sends  │
│ data packet   │
│ with dest IP  │
└──────┬────────┘
       │
       ▼
┌───────────────┐       ┌───────────────┐       ┌───────────────┐
│ Router reads  │──────▶│ Next router   │──────▶│ Destination   │
│ IP address   │       │ or device     │       │ device        │
└───────────────┘       └───────────────┘       └───────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Do you think IPv4 addresses are still enough for all internet devices? Commit to yes or no.

Common Belief:IPv4 addresses are enough because 4 billion is a huge number.

Tap to reveal reality

Quick: Do you think private IP addresses can be used to communicate directly over the internet? Commit to yes or no.

Common Belief:Private IP addresses can be used to access the internet directly.

Tap to reveal reality

Quick: Do you think IPv6 addresses are just longer IPv4 addresses? Commit to yes or no.

Common Belief:IPv6 is just a longer version of IPv4 with the same structure.

Tap to reveal reality

Quick: Do you think IP addresses identify a device permanently? Commit to yes or no.

Common Belief:An IP address always identifies the same device forever.

Tap to reveal reality

Expert Zone

1

IPv6 supports features like auto-configuration and multicast that simplify network management, which many beginners overlook.

2

The transition from IPv4 to IPv6 involves complex strategies like dual-stack and tunneling to maintain compatibility.

3

Subnetting in IPv6 is vastly different and more flexible than in IPv4, affecting how networks are designed.

When NOT to use

IPv6 is not yet fully supported in all legacy systems or some small networks where IPv4 suffices. In such cases, using IPv4 with Network Address Translation (NAT) is still common. Also, for very simple local networks without internet access, static private IPv4 addresses may be easier to manage.

Production Patterns

In real-world networks, IPv6 is often deployed alongside IPv4 (dual-stack) to ensure compatibility. Large organizations use IPv6 for scalability and security improvements. ISPs assign public IPv6 addresses to customers, while home routers use private IPv4 addresses internally. Network engineers use subnetting and address planning to optimize IP usage and routing efficiency.

Connections

Domain Name System (DNS)

DNS translates human-friendly domain names into IP addresses.

Understanding IP addresses helps grasp how DNS connects names to numbers, enabling easy website access.

Postal Addressing System

Both systems assign unique addresses to locations for delivery purposes.

Knowing how postal addresses work clarifies why IP addresses must be unique and structured.

Telephone Numbering

Telephone numbers and IP addresses both route communication to the correct endpoint.

Recognizing this similarity helps understand the importance of numbering plans and routing.

Common Pitfalls

#1Using the same IP address for multiple devices on a network.

Wrong approach:Device A IP: 192.168.1.10 Device B IP: 192.168.1.10

Correct approach:Device A IP: 192.168.1.10 Device B IP: 192.168.1.11

Root cause:Not understanding that IP addresses must be unique within the same network to avoid conflicts.

#2Trying to access a device with a private IP address directly from the internet.

Wrong approach:Accessing 192.168.1.5 from a public internet connection.

Correct approach:Accessing the device through a public IP address or VPN that routes to the private IP.

Root cause:Misunderstanding the role of private vs public IP addresses and network security.

#3Writing IPv6 addresses without proper compression or with invalid characters.

Wrong approach:2001:0db8:0000:0000:0000:0000:1428:57abg

Correct approach:2001:db8::1428:57ab

Root cause:Lack of knowledge about valid hexadecimal characters and IPv6 compression rules.

Key Takeaways

IP addresses are unique numbers that identify devices on networks, enabling communication.

IPv4 uses a 32-bit format with four decimal numbers, but its limited size led to the creation of IPv6 with 128 bits.

IPv6 addresses are longer and use hexadecimal notation, allowing for many more devices to connect.

Private IP addresses are used inside local networks and cannot be accessed directly from the internet.

Routers use IP addresses to direct data packets, making the internet a vast, interconnected system.