What is a DNS entry and what types are there?

The Domain Name System (DNS) has been used since the mid-1980s to assign a fixed address to a domain according to Internet Protocol Version 4 (IPv4) or Version 6 (IPv6). This is necessary because communication does not rely on an address made up of letters, like a postal address, but solely on a numerical code - similar to a globally unique phone number. It consists of a decentralised network of servers (nameservers), from which a client can retrieve the necessary DNS entry (record) for a domain. These entries store various information, including redirection to IPv4 and IPv6, mail servers associated with the domain, or subdomains.

What is a DNS Entry?

A DNS entry is a simple plaintext line that stores all relevant data in a uniform syntax. When a computer needs to contact a specific domain, for example, to access a website or deliver an email, it queries the relevant DNS entry from the nameserver registered for the network connection. The response consists of one or more of the following records:

• SOA Record: Parameters concerning the nameserver's zone
• NS Record: List of nameservers responsible for queries in a zone
• A-Record: The IPv4 address assigned to a domain
• AAAA Record: The IPv6 address assigned to a domain
• CNAME Record: Redirects a name to another name
• ALIAS Record: Similar to CNAME, but can reuse names multiple times
• MX Record: Mail server responsible for a domain
• PTR Record: Resolves an IP address to a domain
• TXT Record: Custom text entry for DMARC or SPF

How is a DNS Entry Structured?

A DNS entry follows a fixed command syntax defined as a public standard. Its exact content varies slightly between different records but largely follows an identical structure:

() () ()

The information in parentheses is optional and does not need to be defined if it is either not relevant or should be taken from the standard configuration. In particular, Time-To-Live (TTL) - the duration of storage time in the cache - and the class IN for Internet usually do not require manual adjustment. However, mandatory are the domain name, the type of entry, and the content, which consists of an IP address, a reference to another domain, or any text in the case of TXT. Additionally, a nameserver requires a DNS entry for the A-record or the CNAME.

Who is responsible for a DNS entry?

The technical administrator of a web address is responsible for managing the records in the DNS, entering the relevant data into a nameserver they use. Typically, the registrar responsible for managing their domains provides them with their own nameservers. However, it is also possible to use external providers to, for example, increase global performance or minimise the risk of downtime in the event of a Distributed Denial of Service (DDoS) attack. Some well-known operators of global DNS Hosting Services include Cloudflare, FreeDNS, Hurricane Electric Internet Services, or the renowned domain provider Namecheap.

How to create or modify a DNS entry?

Access to the DNS configuration is done through a web interface, which domain owners can find in the customer area of their provider. When booked in conjunction with web hosting or a Virtual Private Server or Dedicated Server, it is usually possible to simply adopt the pre-set DNS entry. Otherwise, the relevant information can be entered via a form that generates a standardised DNS entry from it. During this conversion, a check is also carried out to ensure correct details - for example, whether IP addresses and domains have been correctly specified.

Tip: Also, learn about domain security features such as DNSSEC or Domain Guard.

Image credit:
Markus Winkler on Pixabay