Domain Name System (DNS)

Learn the basics of the Domain Name System (DNS) and configure a domain name for your server with Gandi.net.

You will need

A server with a public IP address
A Gandi account that is the administrator or technical contact for a domain

Recommended reading

Unix Networking

On this page

Presentation

DNS zone

A DNS zone is a subset of the domain name space for which administrative responsibility has been delegated to a single manager.

DNS zone file

As the manager of a DNS zone, you can modify the DNS zone file, a text file which describes that zone. It contains mappings between domain name and IP addresses and other resources, in the form of resource records.

A resource record is described by one line in the following format:

name   ttl   record class   record type   record data

The meaning of each field is:

name - Subdomain name (or @ for the domain itself).
ttl - Time during which DNS resolution of this record should be cached.
record class - Namespace of the record information, usually IN for the Internet.
record type - Type of record.
record data - Record data (depending on the record type).

DNS record types

There are multiple record types. These are some of the most common:

Type	Description	Function
`A`	Address record	Maps a domain name to an IPv4 address.
`AAAA`	IPv6 address record	Maps a domain name to an IPv6 address.
`CNAME`	Canonical name record	Alias of one name to another (e.g. `www`).
`MX`	Mail exchange record	Maps a domain name to a list of message transfer agents.
`SOA`	Start of authority	Authoritative information about the zone, e.g. primary name server & email of the domain administrator.
`TXT`	Text record	Arbitrary machine-readable data.

DNS record example

Let’s look at a real example which you might find in a zone file:

name   ttl   record class   record type   record data
@      1800  IN             A             18.213.200.101

Assuming this is the zone file for the domain example.com, here is how to read that record:

It is an Internet record (IN).
The @ name indicates that it concerns the domain example.com itself.
It is an A record, meaning that it maps example.com to the IPv4 address 18.213.200.101.
It defines a cache time of 1800 seconds (30 minutes) during which clients will not perform DNS resolution again if they have the mapping already.

DNS subdomain record example

Let’s look at another example:

name   ttl   record class   record type   record data
blog   300   IN             A             3.120.180.32

Assuming this is the zone file for the domain example.com, here is how to read that record:

It is an Internet record (IN).
It concerns the subdomain blog.example.com.
It is an A record, meaning that it maps blog.example.com to the IPv4 address 3.120.180.32.
It defines a cache time of 300 seconds (5 minutes) during which clients will not perform DNS resolution again if they have the mapping already.

Managing DNS on Gandi.net

Buying a domain name

Most web hosting companies like Gandi allow you to easily check whether a domain name is available, i.e. whether there is already a manager for that subset of the DNS hierarchy, or if you are free to buy it for yourself.

Check out their shop to see if your dream domain name is available.

Configuring a domain

Once you have bought a domain name, you access its management interface from your account:

Configuring the domain’s DNS zone

Gandi offers many services such as email accounts or SSL certificates. The one that interests us is the management of the domain’s DNS zone:

By default, Gandi displays the DNS zone in a human-readable table.

Seeing the raw DNS zone text

Advanced users can also see and edit the real DNS zone file:

Adding a DNS record

The interface allows you to very easily add a DNS record. For example, this screenshot shows how to add an example subdomain pointing to the IP address 1.1.1.1:

ArchiDep

Architecture & Deployment