css thumbnailIn this lesson we will look at understanding the DNS “Domain Name System” and how web addresses work on the internet.

Have you ever wondered how your computer knows how to find the correct web server when you type in a web address?

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When you type in a website, e.g. www.example.org your computer has to perform a lookup to translate that address into something it understands.

The computer looks up “www.example.org” in a big list, and translates the address into an IP Address.

An IP Address is a list of numbers which tells the computer how to find the correct web server for the web site you asked for. An IP address is usually in the form of four numbers separated by dots, for example 127.0.0.1. The maximum for each number is 255, so IP address range from 0.0.0.0 to 255.255.255.255.

(Note: There is a new form of IP addresses known as IPv6 which is six numbers separated by “:” characters. You can think of them as being basically the same idea but longer numbers! So don’t be confused if you see an IP address that doesn’t look like 0.0.0.0 – it’s just an IPv6 address.)

This ‘big list’ where the computer looks up the IP address is called the Domain Name System, which is often shortened to DNS.

When you register a domain name, for example, www.free-online-training-courses.com you have ownership of that address. You can point it at any IP address you like.

The domain name is just a name – it doesn’t come with a web host… for that you have to get a web host! See our earlier lessons on web hosting to understand how to do this.

There are a number of companies which provide access to registering new domain names. When you buy a domain name you can log into the portal the company provides and edit the DNS records for your domain name.

So, perhaps when you register the domain name you have already purchased a web host. And you know that your web host has assigned you the IP address 127.0.0.1.
So you can log into your DNS service and change the IP address associated with your domain name to 127.0.0.1.

This causes the DNS changes to ‘propagate’. This means that the big list of DNS addresses is updated all around the world. Sometimes this takes a few hours.

Then, whenever you type into a browser your domain name, e.g. www.example.org the computer will look up your domain name, find the IP address (127.0.0.1) and then it will ask your web host for your website.

At this point the web server software on your host will respond. And you already understand something about how this works from our earlier lessons!

Now you are beginning to get an idea of the entire workings of the internet and web browsers in more detail. This knowledge will help you greatly as you learn to create websites.


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