Please note that this is not too technical content.

Networks: What I Actually Learned (Not from Cisco)

1. Addressing
2. Internet
3. Subnetting
4. Routing

Today, almost everyone has an internet connection. Also, there might not be a day without us using the internet. This includes organizations, from governments to schools, your social media interactions, and your online game. Even though fewer people have wondered about what the internet is. Who owns it? or how does it work. Many will live their lives without knowing what is the rules of the ISP they are paying bills to.

So here's what I've picked up from 42 projects, debugging my own setup, and building web apps.

IP Addressing: Your Device's ID

An IP address is basically an identity for a device on the internet. Like a phone number, but for computers.

You've heard of IPv4 and IPv6. IPv4 is still everywhere. It has about 4 billion addresses, which sounded huge back in the day, but now it's not enough. That's why we have IPv6, but most people and companies still use IPv4 because switching is slow.

The real trick is that not every IP is public. Private IPs live inside your home or school network. They can't be reached directly from the outside. That's fine, because your router handles the translation.

Subnetting: Slicing the Network

Why subnet? Two reasons.

First, to save IPs. Instead of giving a whole class A range to a small office, you give just what they need.

Second, to organize. Think of a company: finance team in one subnet, engineering in another. It keeps things clean and secure.

In Netpractice (a 42 project), there was an exercise with two hosts and two routers. They had almost the same address range, which confused the routers. Subnetting fixed it by separating them into different logical networks.

CIDR notation like /24 just means: out of 32 bits, we reserve 24 for the network part. The remaining 8 bits are for devices inside that network.

No binary math needed. You just need to know that bigger number after slash = smaller network.

Routing: Getting Packets Where They Need to Go

A router doesn't magically know where everything is. It has a routing table.

When a packet arrives, the router checks its destination against the table. If there's a match, it sends the packet to the next hop. If not, it does nothing (or sends it to a default gateway, if one is set).

Think of a routing table entry as a signpost: "If you're going to network X, go via this next router."

The gateway is simply the door that connects your local network to other networks (including the internet). When your device wants to talk to something outside, it sends the traffic to the gateway.

Who Actually Owns the Internet?

No one person or company. The internet is a network of networks.

ISPs (Internet Service Providers) give you access. They connect to larger ISPs, which connect to global backbone networks. Together, that's the internet.

So when you pay your ISP, you're paying for a pipe to join this massive, decentralized system.

What Taught Me This Stuff

Theory is fine, but projects made it stick.

• Netpractice: the whole project is all about filling and connecting networks, filling routing tables. No Cisco CLI, just logic.
• Born to Be Root: I had to set up a Linux server with proper partitions and network config. You learn quickly when things don't work.
• Inception: Docker and Docker Compose taught me how containers talk to each other over internal networks. Service names become hostnames. That's DNS in action.
• Web dev: When you deploy a backend and a database, you have to make sure they can reach each other. That's routing and addressing in real life.

I've also debugged real issues. Once, a website was blocked by the network manager at school. VPN fixed it. Another time, a site wouldn't respond, so I changed my DNS server. Small things, but you only know they work if you understand what's happening underneath.

Of course I will not mention that I studied the Network+ certificate!

The Takeaway

You don't need to be a network engineer to understand how the internet works. You just need to break things and fix them a few times.

Next time your internet goes down, don't just restart the router. Ask yourself: Is it addressing? Routing? DNS? The ISP?

You might be surprised how often the answer is simple.