IP Addressing

What Is an IP Address?

IP stands for:

Internet Protocol

An IP address is a unique number assigned to a device on a network.

Every device connected to:

• The internet
• A local network (like home Wi-Fi)

has an IP address.

Example:

192.168.1.10

This is called an IPv4 address.

IPv4 Structure

IPv4 addresses look like this:

192.168.1.10

It has four numbers separated by dots.

Each number:

• Ranges from 0 to 255
• Is called an octet
• Is 8 bits in binary

Example in binary:

11000000.10101000.00000001.00001010

You do not usually need to work with the binary form, but internally that is how computers understand it.

Public vs Private IP Addresses

There are two main types:

Public IP

• Used on the internet
• Assigned by your Internet Service Provider

Private IP

• Used inside local networks
• Not directly visible on the internet

Common private IP ranges:

192.168.x.x
10.x.x.x
172.16.x.x to 172.31.x.x

Example:

192.168.1.5

That is usually a home device.

Localhost

There is a special IP address:

127.0.0.1

This is called localhost.

It means:

"This computer."

It allows a machine to talk to itself.

IPv6

IPv4 has limited addresses (about 4.3 billion).

Because the internet grew so much, a newer system was created:

IPv6

Example:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

IPv6:

• Uses hexadecimal numbers
• Is much longer
• Supports far more devices

Most modern systems support both IPv4 and IPv6.

Subnet Mask (Basic Idea)

A subnet mask determines:

Which part of the IP address identifies the network

Which part identifies the device

Example:

IP address:

192.168.1.10

Subnet mask:

255.255.255.0

This usually means:

• 192.168.1 → Network
• 10 → Device

You may also see it written as:

192.168.1.10/24

The /24 means 24 bits are used for the network.

How Data Travels Using IP

When you visit a website:

1. Your computer asks DNS for the IP address.
2. DNS returns an IP address.
3. Your computer sends data to that IP.
4. The server responds back to your IP.

This is how communication happens across the internet.

Viewing Your IP Address

On Linux or macOS:

ip addr

Or:

ifconfig

On Windows:

ipconfig

Testing Connectivity

You can test connection to another device using ping.

Example:

ping 8.8.8.8

This sends small packets to check if the destination responds.

On Windows:

ping 8.8.8.8

Example: Basic IP Configuration Output (Windows)

ipconfig

You might see:

IPv4 Address. . . . . . . . . . : 192.168.1.20
Subnet Mask . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . : 192.168.1.1

Default Gateway is usually your router.

Summary of Important Terms

IP Address

Unique number identifying a device.

IPv4

32-bit address format like 192.168.1.10

IPv6

128-bit address format like 2001:db8::1

Public IP

Used on the internet.

Private IP

Used inside local networks.

Subnet Mask

Defines network portion vs device portion.

Gateway

Device that connects your network to another network.