How does DNS work? Types and operating modes

As part of the anatomy of a URL, as we explained here, there are one important item with lot’s of ramifications: the Domain Name.

The Domain Name in a URL is part of DNS (Domain Name System) which is a name management system for network connected resources. It basically translates human-readable domain names into numerical IP Addresses needed for the purpose of locating and identifying clients and servers throughout a network.

DNS allows data to be stored in the entry, allowing different types of records to be created, all with different purposes, let’s go through them:

Standard Records:


The A record maps a name to one or more IP addresses, when the IP are known and stable,
ex: IN A


Maps a IPv6 address record to a hostname
ex: www IN AAAA 2001:db8::3


Makes one domain name an alias of another. The aliased domain gets all the subdomains and DNS records of the original. Ideal if you want to associate a subdomain to an already existing A record.
ex: to – knowing that “” has a A record pointing to the server IP.


An email-associated record, maps a domain name to the email server for that domain.
ex: 300 IN MX 10

The record says all emails going to should go to the IP behind the record with priority 10.


Implements a IPv4 Reverse Lookup for the IP address of the domain and it’s basically the opposite of a A record. One maps a name to a IP and the other a IP to a name. When you have the PTR record setup, you can get the associated domain/hostname. An A record should exist for every PTR record.

Ex: if an A Record points to, a PTR record would look like: 3600 IN PTR


Allows an administrator to add text to the DNS record, and it’s commonly used to implement a SPF (Sender policy framework) as a method to fight spam. In the TXT record, we can declare a list of authorized hostnames and IP’s from where email can originate from.
Ex: v=spf1 a mx ip4: -all

Use a DNS service provider

Services like Cloudflare make all of this easier: Clean and easy interface plenty of helpful resources, improvements in the website performance, caching, security and it’s free.

You’ll see it’s much easier to manage your DNS settings using a service like this – you can tank me later.