IP Addresses: The Internet’s Hidden Street Signs!

5 min readOct 5, 2024

Have you ever wondered how devices on the internet find each other in the vast digital landscape? Enter IP addresses, the unsung heroes of the internet! Let’s dive into the fascinating world of these digital identifiers and uncover their secrets.

What Are IP Addresses?

IP addresses are like the street signs of the internet. They’re Layer 3 addresses assigned by network administrators to identify specific devices on a network. Just as every house on a street needs a unique number, every device on a network needs its own IP address.

Picture this: Oxford Street has five houses, each with a unique number — Oxford 1, Oxford 2, Oxford 3, and so on. You can’t have multiple houses with the same number on the same street. However, you can have a house on Charlie Street with the number Charlie 1. IP addresses work the same way!

The Anatomy of an IP Address

An IP address is a 32-bit number, divided into four octets (8 bits each). It looks something like this: 192.168.1.1. Each octet can range from 0 to 255.

192     .     168     .     1       .     1
11000000 . 10101000 . 00000001 . 00000001

IP Address Classes

Traditionally, IP addresses were divided into five classes. Let’s break them down in detail:

Class A

The first octet’s first bit = 0
Start: 0000 0000 (0)
End: 0111 1111 (127)
Actual range: 1.0.0.0 to 126.255.255.255 (0 is reserved for default network, 127 for loopback)
Network ID: 1st octet
Host ID: 2nd, 3rd, 4th octets

Class B

The first octet’s first two bits = 10
Start: 1000 0000 (128)
End: 1011 1111 (191)
Range: 128.0.0.0 to 191.255.255.255
Network ID: 1st and 2nd octets
Host ID: 3rd and 4th octets

Class C

The first octet’s first three bits = 110
Start: 1100 0000 (192)
End: 1101 1111 (223)
Range: 192.0.0.0 to 223.255.255.255
Network ID: 1st, 2nd, and 3rd octets
Host ID: 4th octet

Class D (Multicast)

The first octet’s first four bits = 1110
Start: 1110 0000 (224)
End: 1110 1111 (239)
Range: 224.0.0.0 to 239.255.255.255

Class E (Reserved for future use)

The first octet’s first five bits = 1111
Start: 1111 0000 (240)
End: 1111 1111 (255)
Range: 240.0.0.0 to 255.255.255.255

Each class has different proportions of network and host portions, allowing for various network sizes. This classification system helped in the early days of the Internet to organize and allocate IP addresses efficiently.

Subnet Masks: The Secret Decoder Ring

Subnet masks are the key to understanding which part of an IP address represents the network and which part represents the host. They look like IP addresses but work differently:

1s in the subnet mask indicate the network portion
0s indicate the host portion

For example: IP Address: 10.1.1.1 Subnet Mask: 255.255.0.0 (11111111.11111111.00000000.00000000 in binary)

This tells us that 10.1 is the network portion (like the street name) and .1.1 is the host portion (like the house number).

CIDR: The Modern Approach

Classless Inter-Domain Routing (CIDR) has replaced the traditional class system, revolutionizing how we think about IP address allocation and subnetting. CIDR notation provides a more flexible and efficient way to define network and host portions of an IP address.

What is CIDR Notation?

CIDR uses a simple notation that appends a forward slash (/) followed by a number to an IP address. This number represents the count of contiguous 1s in the subnet mask, indicating how many bits are used for the network portion.

For example:

10.1.1.1/24 means the first 24 bits are the network portion
This is equivalent to a subnet mask of 255.255.255.0

CIDR and Subnet Masks

CIDR notation directly correlates to subnet masks. Here are some common examples:

/32 → 255.255.255.255 (a single host)
/24 → 255.255.255.0
/16 → 255.255.0.0
/8 → 255.0.0.0

But CIDR allows for much more granular subnetting. For instance:

/19 → 255.255.224.0
/21 → 255.255.248.0

Advantages of CIDR

Variable Length Subnet Masks (VLSM): CIDR allows for subnet masks of any length, not just on octet boundaries. This enables more efficient use of IP address space.
Supernetting: CIDR makes it possible to combine multiple smaller networks into a larger one, simplifying routing tables.
More Flexible Network Design: Network administrators can create subnets that precisely fit their needs, rather than being constrained by class boundaries.
Improved Routing Efficiency: By allowing route aggregation, CIDR helps keep routing tables smaller and more manageable.

How to Read CIDR Notation

When you see an IP address with CIDR notation, remember:

The number after the slash represents the number of contiguous 1s in the subnet mask.
These 1s, starting from the left, define the network portion of the address.
The remaining bits (0s in the subnet mask) define the host portion.

For example, in 192.168.1.0/26:

The first 26 bits are the network portion
The last 6 bits are available for host addresses

This allows for a much more nuanced approach to network design and IP address allocation compared to the rigid class-based system.

The Magic of Routing

When data travels across the internet, it hops from router to router, much like a package being passed between delivery trucks. Routers use the network portion of the IP address to determine the best path, considering factors like:

Load balancing
Bandwidth
Hop count

It’s a complex dance orchestrated by routing protocols, ensuring your cat videos arrive at their destination as quickly as possible!

Public vs. Private IP Addresses

Not all IP addresses are created equal. Some are meant for the public internet, while others are for private networks. Thanks to Network Address Translation (NAT), multiple devices can share a single public IP address, allowing for efficient use of the limited IPv4 address space.

The Future: IPv6

With the explosion of internet-connected devices, we’re running out of IPv4 addresses. Enter IPv6, with its mind-boggling 128-bit addresses, ensuring we won’t run out of unique identifiers anytime soon!

Conclusion

IP addresses are the unsung heroes of the internet, guiding our data through the complex web of networks. From their humble beginnings as class-based identifiers to the modern CIDR notation, they continue to evolve, ensuring our digital world remains connected and addressable.

So the next time you’re browsing the web or sending an email, spare a thought for the hardworking IP addresses making it all possible. They’re why you can find one specific cat video among billions of other cat videos on the internet!