The Venetian carnival tradition is most famous for its distinctive masks. Photograph by Frank Kovalchek via Wikimedia Commons (CC BY 2.0).

History of Venetian Carnival Masks

TCP/IP Subnet Masking Explained

A Brief History of TCP/IP

Back in the ancient days of the internet (a.k.a. the 1970s), a bunch of brilliant people at DARPA were trying to connect computers across different networks.

They came up with TCP/IP, a communication protocol that made sure computers could talk to each other without getting confused.

Think of it as the internet’s universal translator.

Now, as networks grew, engineers realized that assigning a unique IP address to every device on Earth was going to be a nightmare (and IPv6 hadn’t saved us yet).

So, subnetting was introduced to break large networks into smaller, more manageable chunks. Enter subnet masks—the unsung heroes of the networking world.

More about TCP/IP on Wikipedia

What’s a Subnet Mask? (And Why Should You Care?)

A subnet mask is like an address filter that determines which part of an IP address belongs to the network and which part belongs to the host (a fancy way of saying “device”).

It helps organize networks, improves security, and reduces network congestion.

A typical subnet mask looks something like this:
255.255.255.0

But what does that actually mean? Time to break it down.

Understanding Octets (No, Not an Alien Species)

An IP address is made up of four octets (groups of 8 bits), separated by dots. Example:

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192.168.1.10

Each octet can have a value between 0 and 255 because 8 bits = 2^8 = 256 possible values.

Now, a subnet mask tells us which part of the address is the “network” and which part is the “host.” Example:

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IP:      192.168.1.10
Subnet:  255.255.255.0

• The 255 parts mean “this belongs to the network.”
• The 0 part means “this belongs to the host.”

In this case, the network is 192.168.1.0, and all addresses from 192.168.1.1 to 192.168.1.254 belong to this network.

Subnetting on Wikipedia

Example: Why Does Subnetting Matter?

Let’s say you run a cyber café (because apparently, it’s 2005 again), and you have 100 computers. You could:

1. Get a gigantic network where every computer sees every other computer’s traffic (terrible for security).

2. Use subnetting to divide them into smaller groups, like:

   • 192.168.1.0/25 → For wired PCs
   • 192.168.1.128/25 → For Wi-Fi users

This keeps things clean and efficient.

CIDR Notation (Because Dots Weren’t Confusing Enough)

Instead of writing subnet masks like 255.255.255.0, we use CIDR (Classless Inter-Domain Routing) notation:

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192.168.1.0/24

The /24 means 24 bits are reserved for the network. The remaining bits (8 bits) are for hosts.

Common CIDR Blocks

So, if you see something like /30, that means you only have 2 usable IP addresses (great for point-to-point connections).

Real-World Subnetting Example

Let’s say your ISP gives you a public IP block:
200.100.50.0/28

That /28 tells us:

• Network: 200.100.50.0
• Subnet mask: 255.255.255.240
• Total addresses: 16
• Usable addresses: 14 (2 are reserved for network & broadcast)

You can assign these 14 IPs to your web servers, routers, or secret hacking lab.

Conclusion

Subnet masking is one of those things that seems boring until you realize it’s what keeps the internet running smoothly. Whether you’re setting up a home network or managing a corporate data center, knowing how subnet masks work will save you from network chaos.

Key Ideas

Reference Links

• Internet Protocol Suite (TCP/IP)
• Subnetting
• CIDR