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13.09.2021 FQDN – Definition, structure, syntax and examplesThere is much more behind a domain than one imagines. They conceal a unique technical cosmos. Their resolution in the domain name system (DNS) is a complex process, as each computer, each domain and each IP address must be unambiguously identifiable. How does this work? This is where the so-called fully qualified domain name (short FQDN) comes into play.Fully qualified domain name – a definition The term fully qualified domain refers to a domain name that fully specifies the unique and exact location of a domain name within the DNS. The DNS provides the syntax. An FQDN is made up of individual labels that are each delimited by a dot and represent the different levels of the FQDN. [hostname].[domain].[tld] -> [www].[internetx].[com] The FQDN is relevant whenever a connection to the host is established. The DNS server resolves the hostname to its IP address by querying the DNS database. So, an FQDN shows the absolute path to a host and displays its IP address in a complete form that is legible to users. There are a few rules for these so-called “absolute addresses”:
How is a fully qualified domain name structured?The hierarchy levels of an FQDN are read from right to left. The root label, also known as the null label, takes the highest hierarchy level and is therefore, as the name suggests, the root of the DNS system. It consists of an empty string and is indicated with a simple full stop. As all browsers now add this dot automatically, users no longer need to enter it. The further right it is positioned, the higher the level held in the DNS. So the domain holds a higher level than a subdomain. Let’s take a look at the structure of an FQDN by using www.internetx.com as an example:  Root domainWhile most people are aware of the reading direction for domain names, the root domain usually remains hidden. It is the basis of the DNS system and is also called null or root label. It is made up of an empty zero-length string consisting of a single octet of zeros. In an FQDN, which strictly follows syntax, it is simply indicated by a dot. Technically, a top-level domain is therefore in actual fact also a subdomain of the root domain. The root domain itself is automatically added by browsers, which is why they are generally not included in the FQDN. Top-level domainIn our example, the top-level domain is ".com". Under this domain extension, the actual desired domain name can be selected in accordance with the guidelines of the respective registry. Second-level domainThe second-level domain constitutes the address referred to as “domain”. Occasionally, the registry specifies that the second-level domain is predetermined and the selectable name is located on the third level – as is the case with .uk domains. Under .uk, domains can only be registered under the extensions .co.uk, .org.uk etc. but not directly under .uk. The same applies to domains under the Australian top-level domain. Starting March 2022, it will be possible to register second-level domains as domain names directly under .au. Until then, only third-level registrations are possible, e.g. under .com.au. HostnameAs mentioned before, FQDNs are read from right to left. Between the second-level domain and the hostname, further subdomains may be included, numbered consecutively as third-level domain, fourth-level domain and so on. Farthest left, the hostname follows at the end. In our example https://www.internetx.com/domains/, the hostname is “www.” So, while a host name is always a subdomain, a subdomain is not necessarily already the hostname. What is the difference between FQDN, FQHN and PQDN?Via a fully qualified hostname (FQHN), a query reaches a unique and unambiguously identifiable computer. Its address is indicated through an IP or an FQDN. An example: The computer with the name “mycomputer” can either be reached via the FQDN mycomputer.internetx.com or via an IP address, such as the fictive example 85.236.36.86. By contrast, the partially qualified domain name (PQDN) is a relative name for a domain. It does not provide the complete path to the top-level domain. The name “mycomputer” is the PQDN in our example mycomputer.internetx.com. A tip for further reading: 3 domain strategies for your multilingual website architecture Looking for interesting domains to add to your portfolio? Don’t have an AutoDNS account yet? You should get one today. Read here to find out why. Domain management with AutoDNS Welcome back!How is FQDN resolved?Domain Name System Name Resolution
An alternative to the hosts file is to use a DNS Server. DNS Servers store FQDN-to-IP address translations. A computer runs the DNS client called the DNS resolver, which is configured with the IP address of the DNS Server.
What is the process of resolving a hostname or FQDN to an IP address?Host Name Resolution is the process by which a host determines the IP address of another host given its host name or fully qualified domain name (FQDN) on a TCP/IP network.
What type of DNS record is used for resolving an IP address to a hostname FQDN?The A record is one of the most commonly used record types in any DNS system. An A record is actually an address record, which means it maps a fully qualified domain name (FQDN) to an IP address.
How do I use FQDN instead of IP address?Using a FQDN instead of an IP address means that, if you were to migrate your service to a server with a different IP address, you would be able to simply change the record in DNS rather than try and find everywhere that the IP address is used.
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How does the domain name system (dns) resolve fully qualified domain names (fqdn) to ip addresses?
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