What is DNS?

I am pretty sure you already saw this term showing up configuring your internet connection, or when you were typing the address of a website incorrectly in your browser. But what is DNS and how does it work?

Another acronym? Yes!

DNS stands for Domain Name System and what it does is really simple (for normal users).

When you surf to letsmakeitsimple.tech, you ever asked yourself the question why you could type this human readable name instead of an IP address?

This is where our friend DNS comes in. The server where this site is running has an IP address of 45.87.81.182. But imagine you had to know this address for all sites you surf to. Not scalable right? You would soon reach the limit of the human being’s memory :).

Forward and reverse DNS lookups

DNS does the translation of human readable names into IP addresses. So your computer know where to connect to. This is called a forward DNS lookup.

But DNS also does the other way around. It can translate IP address to human readable names. This is called a reverse DNS lookup. But …. why would we use this?

One of the most common use of reverse DNS lookups is spam prevention. Mail severs will check if the IP from the sender’s mail server matches the sender’s MX (Mail Exchange) records in his domain.

Do not worry to much about the types of DNS records like A, AAAA, CNAME, … We will cover these extensively in another article.

Hands on practice time!

When you want to play a little bit with DNS, open a command prompt (on a Windows machine) or a terminal session on Mac or Linux and type in ‘nslookup’. You will be prompted with a > From there you can type either an IP or a DNS name and it will gets translated in either an DNS name or an IP address.

Also, don’t worry about the non authoritative part. We will also cover this in another article about DNS.