Question

What is the Fully Qualified Domain Name (FQDN)

Answer 1

Structure of the FQDN
Example of an FQDN
The FQDN in Windows
FQDN on macOS
FQDN on Linux

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What is the Fully Qualified Domain Name (FQDN)

The term Fully Qualified Domain Name (FQDN) refers to the complete and unique address necessary to have a presence on the Internet. It is made up of the host name and the domain name and is used to locate and access specific hosts on the Internet using name resolution..

The structure of the FQDN is determined by the domain name system (DNS) and is made up of labels. Each label corresponds to the name of a level in the domain namespace and is separated from the next by a period. It must consist of between 1 and 63 characters, which can be numbers, letters and hyphens (although hyphens cannot really be used when starting a label) and the total characters of the FQDN must not exceed 255.

The Fully Qualified Domain Name consists of at least three labels: the top-level domain , the domain name, and the host name , although subdomains are sometimes included as well. When a domain name does not contain all the necessary labels to make up the FQDN, it is referred to by the PQDN acronym for? Partially Qualified Domain Name ?, which often means that it only consists of the host name. Sometimes "Fully Qualified Host Name" (FQHN) is also used to refer to the FQDN along with the IP address..

Below you can see exactly how the Fully Qualified Domain Name is structured.

Index

1. Structure of the FQDN
2. Example of an FQDN
3. The FQDN in Windows
4. FQDN on macOS
5. FQDN on Linux

Definition

The term Fully Qualified Domain Name (FQDN) refers to the full address of any object present on the Internet. "Fully qualified" indicates that all levels of the domain are specified, which guarantees unique identification. This fully qualified domain name, which can only be mapped to an IP address, contains the host name and domain name, including the top-level domain..

Structure of the FQDN

To better understand the hierarchy of names of the Fully Qualified Domain Name, pay attention to its structure from right to left. The further to the right a label is, the higher it is in the hierarchy representation of the tree diagram . At the highest hierarchical level you can see the root label , so called because it is considered the "root" of the DNS system. It is an empty area and is preceded by a period. However, it is not necessary to add this point in current browsers, since they already do it themselves.

The top - level domain , also known by the acronym TLD (top-level domain) is in the second highest hierarchical level. Some examples are: "es", "com" or "net". To resolve an address, the nameserver searches the directory starting at the specified TLD, and from there it moves to a lower hierarchical level. Once it has been identified and to access the specified page, the host whose name is indicated in the last label of the hierarchy (host name) is contacted.

Schematic representation of the structure of the Fully Qualified Domain Name

Example of an FQDN

The following example illustrates the structure of a Fully Qualified Domain Name:

hosting.ionos.es.

[Hostname]. [Domain]. [TLD]. [Root]

The directory on a nameserver includes the last point to the right of the FQDN.

The root domain label after period remains empty. In our example, the top-level domain ".es" corresponds to the geographic top-level domain, also known by the acronym ccTLD (country code-top level domain). In front of them are generic TLDs like .com or .org, also referred to as gTLD (generic top-level domain).

The top-level domain is followed by the domain name , also known as a second-level tag or second-level domain. In the example it corresponds to "ionos". On the far left we have the host name as a third level label: in our example it is "hosting".

Additional labels for subdomains can be inserted between the second-level domain and the hostname, indicating child areas of the domain. They would then receive the name of third-level domains, fourth-level domains, etc. Their number is only limited by the maximum allowed total length of the FQDN, that is, 255 characters. An example: in the fictional FQDN hosting.example.ionos.es "example" would be a subdomain of "ionos.es" and "hosting" would again be the hostname.

The FQDN in Windows

In Windows, you can find the Fully Qualified Domain Name under the name "Full Computer Name". To find it in Windows 10, you have to type "Control Panel" in the Windows search box. Then click on "System and Security" and then on "System". In the penultimate section of this page you will find the full computer name, which is made up of the computer name (host name) and the domain, also indicated. If the computer was not connected to a domain, only the local host name would be displayed. In Windows 7 you can access this screen by right-clicking "Computer" in the Start menu and selecting "Properties".

The FQDN is displayed as "Full computer name" in Windows Control Panel

It is also possible to access the Windows FQDN through the command line. To do this, enter the following line and press the? Enter? Key:

  echo %COMPUTERNAME%.%USERDNSDOMAIN%  

The Fully Qualified Domain Name of the device will then appear. If the computer is not connected to a domain, the unmodified variable "% USERDNSDOMAIN%" will be displayed after the computer name.

FQDN in Windows with the command line

FQDN on macOS

As long as the computer is connected to a domain, the FQDN of your macOS device will be displayed when you enter the following command line in the terminal and confirm with? Enter ?:

  nombre de host -f  

FQDN on Linux

In Linux, the same command indicated in macOS is also entered on the command line:

  nombre de host -f  

Although it is also possible to use the following command:

  nombre de host --fqdn  

After confirming with? Enter ?, you will receive the Fully Qualified Domain Name, which in case of not being connected to a domain, will show only the host name.

Linux: the FQDN is obtained in the terminal by means of two different commands

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