Welcome to IP Addresses

In this room, you'll learn about one of the most important concepts in networking: IP addresses. Every device connected to a network needs an IP address to communicate, just like every house needs an address to receive mail. Whether you're browsing websites, sending emails, or streaming videos, IP addresses make it all possible.

IP addresses are the foundation of how devices find and talk to each other on networks. Without them, the internet as we know it wouldn't exist. Understanding IP addresses is essential for anyone who wants to:

• Set up home or office networks
• Troubleshoot connectivity issues
• Work in IT or cybersecurity
• Simply understand how the internet works

What You'll Learn

By completing this room, you'll understand:

• What IP addresses are and why we need them
• The difference between IPv4 and IPv6 addresses
• How public and private IP addresses work
• How routers use IP addresses to connect networks
• Practical examples of IP addresses in real networks

Prerequisites

Before starting this room, you should know:

• Basic computer operation
• What a network is (devices connected together)
• Basic network devices (routers and switches)
• No prior IP address knowledge needed - we start from scratch!

How to Approach This Room

1. Read each task carefully, concepts build on each other
2. Don't rush, take time to understand each concept
3. Use the visual demonstrations to see concepts in action
4. Try the knowledge check questions to test your understanding
5. Ask yourself: "Does this make sense in real life?"

Optional Video

This optional video covers the fundamental concepts of IP addresses. It's helpful but not required to complete the room.

An IP (Internet Protocol) address is a unique identifier assigned to every device connected to a network. Think of it like a home address for your computer, phone, or tablet. Just as your home address tells the postal service where to deliver your mail, an IP address tells the network where to send data.

The House Address Analogy

Imagine a street with several houses:

• House 1: 192.168.1.101 (Dad's computer)
• House 2: 192.168.1.102 (Mom's laptop)
• House 3: 192.168.1.103 (Kid's tablet)
• House 4: 192.168.1.104 (Smart TV)

Each device needs its own unique "address" so data knows exactly where to go. If two devices had the same IP address, it would be like two houses having the same address, the mail carrier wouldn't know where to deliver!

Basic Structure of IP Addresses

Most IP addresses you'll encounter look like this: 192.168.1.101

This is called "dotted decimal notation" because:

• It has four numbers separated by dots
• Each number can range from 0 to 255
• The dots separate different parts of the address

What IP Addresses Do

IP addresses have two main jobs:

1. Identification: They uniquely identify each device on a network
2. Location: They provide location information so data knows where to go

How Devices Get IP Addresses

Devices can get IP addresses in two main ways:

• Automatic: From a router using DHCP (Dynamic Host Configuration Protocol)
• Manual: Set by a network administrator (called static IP addressing)

For home networks, automatic assignment is most common, your router automatically gives each device a unique IP address when it connects.

Below is the visual demonstration of router providing ip addresses to each connecting device

Simple Home Network Scenario

Imagine setting up WiFi at home:

1. You connect your router to the internet
2. Your phone connects to the WiFi
3. The router gives your phone an IP address (e.g., 192.168.1.105)
4. Now your phone can communicate with other devices and access the internet
5. Each new device gets its own unique IP address

There are two main versions of IP addresses in use today: IPv4 and IPv6. Think of them like different addressing systems, one is the older system we've been using for decades, and one is the newer system designed for the future.

IPv4: The Original System

IPv4 (Internet Protocol version 4) is what you've seen so far. It looks like this: 192.168.1.1

Key characteristics:

• Uses 32-bit addresses
• Written as four numbers separated by dots
• Each number ranges from 0 to 255
• Provides about 4.3 billion possible addresses

Example IPv4 addresses:

• 192.168.1.1 (common router address)
• 8.8.8.8 (Google's public DNS server)
• 127.0.0.1 (your own computer - "localhost")

IPv6: The New System

IPv6 (Internet Protocol version 6) is the newer format. It looks like this: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

Key characteristics:

• Uses 128-bit addresses
• Written as eight groups of four hexadecimal digits
• Groups separated by colons
• Provides 340 undecillion addresses (that's 340 followed by 36 zeros!)

Example IPv6 addresses:

• 2001:4860:4860::8888 (Google's IPv6 DNS)
• fe80::1 (link-local address)
• ::1 (IPv6 localhost)

Below is the visual explanation of IPv4 and IPv6

Why Do We Need IPv6?

The main reason is simple: we're running out of IPv4 addresses! With only 4.3 billion possible IPv4 addresses and billions of devices connecting the internet (computers, phones, tablets, smart devices, IoT devices), we need more addresses.

Comparison Table: IPv4 vs IPv6

Feature	IPv4	IPv6
Address Size	32 bits	128 bits
Address Format	Decimal numbers (192.168.1.1)	Hexadecimal with colons (2001:db8::1)
Number of Addresses	~4.3 billion	340 undecillion (extremely large)
Address Separation	Dots (.)	Colons (:)
Example	10.0.0.1	2001:0db8:85a3::8a2e:0370:7334
Common Use Today	Most home networks	Growing in use, especially on mobile networks

Real-World Scenario

When you connect to the internet:

• Your home network probably uses IPv4 (like 192.168.1.x)
• Your mobile data might use IPv6 (many cellular networks use IPv6)
• Most websites support both IPv4 and IPv6
• Your device can use both at the same time

The Address Exhaustion Problem

Imagine a city with only 100 possible house numbers. As more houses get built, you eventually run out of numbers! That's what happened with IPv4. IPv6 solves this by providing essentially unlimited addresses, enough for every grain of sand on Earth to have its own IP address!

IP addresses come in two types: public and private. Understanding this distinction is crucial for understanding how home and office networks connect to the internet.

Public IP Addresses: Your Internet Identity

A public IP address is your address on the internet. It's like your home's street address that the postal service uses.

Key points:

• Assigned by your Internet Service Provider (ISP)
• Unique across the entire internet
• Visible to websites and services you visit
• Your router uses this to communicate with the internet

Example: When you visit a website, it sees your public IP address (like 203.0.113.45).

Private IP Addresses: Your Local Network Identity

A private IP address is used inside your local network. It's like room numbers inside your house.

Key points:

• Used only within your local network (home, office, school)
• Not unique globally, many networks use the same private addresses
• Not directly accessible from the internet
• Assigned by your router to your devices

Example: Your phone might have 192.168.1.105 inside your home network.

Why Do We Need Both Systems?

We use both systems because:

1. Conservation: There aren't enough public IPv4 addresses for every device
2. Security: Private IPs aren't directly accessible from the internet
3. Organization: Easy to manage local networks separately

Common Private IP Address Ranges

These IP ranges are reserved for private networks:

Range	Example	Typical Use
10.0.0.0 to 10.255.255.255	10.0.0.1	Large office networks
172.16.0.0 to 172.31.255.255	172.16.0.1	Medium organizations
192.168.0.0 to 192.168.255.255	192.168.1.1	Home networks (most common)

Note: Any device can use these private ranges internally, but they can't be used on the public internet.

How NAT Works (Simplified)

NAT (Network Address Translation) is the magic that makes this work. Think of it like an office receptionist:

• All employees (private IPs) give their mail to the receptionist
• The receptionist puts the office address (public IP) on all outgoing mail
• Incoming mail comes to the office address
• The receptionist knows which employee each piece is for

Your router does the same thing, it keeps track of which device requested what and makes sure responses go to the right place.

Below is the visual demonstration of how a private IP address is converted to a public IP address by a router.

Security Benefit

Private IP addresses provide a security layer:

• Devices with private IPs aren't directly accessible from the internet
• Hackers can't directly attack 192.168.1.105 from the internet
• They only see your router's public IP address
• Your router acts as a firewall protecting your devices

Home Network Scenario

Your home network setup:

1. ISP gives your router a public IP: 203.0.113.45
2. Your router creates a private network: 192.168.1.x
3. Your phone connects: gets 192.168.1.101 (private)
4. Your laptop connects: gets 192.168.1.102 (private)
5. Both devices use 203.0.113.45 (public) when browsing the internet
6. Websites only see 203.0.113.45, not your individual device addresses

Routers are the devices that connect different networks together and direct traffic between them. Think of a router as a postal sorting facility: it looks at the destination address (IP address) on each package (data packet) and decides where to send it next.

How Routers Read IP Addresses

When a router receives data, it checks the destination IP address and asks: "Is this for a device on my local network, or should I send it elsewhere?"

Routing decisions are based on:

1. Local network IPs: If the destination is within the router's own network (like 192.168.1.x), it sends directly to that device
2. Other networks: If the destination is outside (like a website's IP), it forwards the data to the next router

Simple Routing Example

Imagine you're at home and visit google.com:

1. Your computer (192.168.1.101) sends data to your router
2. Router checks: "Is 172.217.14.206 on my 192.168.1.x network? No."
3. Router forwards data to your ISP's router
4. ISP's router checks its routing tables
5. Data travels through multiple routers
6. Eventually reaches Google's network
7. Response comes back through the same path

Default Gateway: Your Exit Door

Your router's IP address on your local network is called the "default gateway." It's the door all your devices use to reach the outside world. Typically:

• Home routers: 192.168.1.1 or 192.168.0.1
• This is the first stop for any data going outside your network

Below is the visual demonstration of Network Routing Decisions

Traceroute: Following the Path

A traceroute shows the path your data takes through routers. Simplified example:

1. Your computer → Home router (192.168.1.1)
2. Home router → ISP router (203.0.113.1)
3. ISP router → Regional router (198.51.100.1)
4. Regional router → Google's network (172.217.14.1)
5. Google's network → Google server (172.217.14.206)

Each "hop" is a router making a decision based on IP addresses.

Practical Troubleshooting Scenario

Problem: "I can access local devices but not the internet."

Troubleshooting steps using IP address knowledge:

1. Check if device has a valid IP address (not 169.254.x.x)
2. Ping the router (default gateway): ping 192.168.1.1
   • Success: Local network works
   • Failure: Problem with router or connection
3. Ping a public IP (like 8.8.8.8 - Google DNS)
   • Success: DNS might be the issue
   • Failure: Internet connection problem
4. Check router's public IP (in router settings)
   • No public IP: ISP connection issue
   • Has public IP: Router configuration issue

Routing Decision Table

Destination IP	Router's Decision
192.168.1.105 (local device)	Send directly to device
192.168.1.255 (broadcast)	Send to all local devices
8.8.8.8 (Google DNS)	Forward to ISP
10.0.0.5 (different private network)	Block or forward based on rules

Why This Matters

Understanding how routers use IP addresses helps you:

• Troubleshoot network problems
• Set up home networks correctly
• Understand why some devices can't communicate
• Appreciate how data travels across the internet

Congratulations! You've successfully completed this introduction to IP addresses. Let's review what you've learned and how you can apply this knowledge.

What You've Learned

In this room, you've covered the essential fundamentals of IP addresses:

• What IP addresses are and why every network device needs one
• The difference between IPv4 and IPv6 address formats
• How public and private IP addresses work together
• The role routers play in directing traffic using IP addresses
• Practical scenarios showing IP addresses in action

Key Takeaways

• Every device needs an address: IP addresses uniquely identify devices on networks, similar to how home addresses identify houses
• Two main versions: IPv4 (older, 4-number format) and IPv6 (newer, hexadecimal format)
• Public vs Private: Public IPs are for the internet, private IPs are for local networks
• Router as traffic director: Routers use IP addresses to decide where to send data
• Conservation through sharing: Multiple private devices can share one public IP using NAT

What You Should Now Understand

After completing this room, you should be able to:

• Explain what an IP address is to someone new to networking
• Recognize IPv4 and IPv6 address formats when you see them
• Understand why your phone has a different IP at home vs. on mobile data
• Troubleshoot basic connectivity issues using IP address knowledge
• Set up simple home networks with proper IP addressing