What is a DNS zone and which DNS types exist?

The Domain Name System (=DNS) is divided into many separately managed areas. With the help of DNS zones, a distinction is made between the individual areas so that a query can be correctly assigned. A DNS zone is usually managed by companies or administrators themselves. It represents, so to speak, an administrative area that enables precise control of the DNS components.

For the administration of a DNS zone a name server is necessary, whereupon the zone is stored in a zone file. Usually, at least 2 name servers are used for a domain to increase availability in case of server failures. These are called primary and secondary nameservers respectively. The zone file is stored on the primary nameserver and then transferred to the secondary nameserver.

A DNS zone contains several resource records, which are used to link the various services offered by a domain or subdomain to the domain name. The resource records are divided into different types, which are entered into the zone depending on the service offered.

How is a DNS zone structured?

In order to create a DNS zone, further information is required in addition to the resource records, which is contained in the zone header:

• Template Name

  ---

  Enter the name of the template here to be able to distinguish it from others later.
• Primary DNS

  ---

  Enter here the primary DNS server to be accessed first in case of a request.
• Email

  ---

  Enter your email address here.
• Serial

  ---

  This is the serial number of the zone. This is automatically incremented by one with each change. (Will be set automatically.)
• Refresh

  ---

  This is the number of seconds between refresh requests from secondary and slave name servers. (Will be set automatically.)
• Retry

  ---

  This is the number of seconds the secondary or slave name server waits before retrying, if the last attempt failed. (Will be set automatically.)
• Expire

  ---

  This is the number of seconds a primary or secondary name server waits before considering the data stale, if the primary name server is unreachable. (Will be set automatically.)
• Minimum

  ---

  This value was previously used to determine the minimum TTL and is used for negative caching. This is the default TTL if the domain does not specify a TTL. (Will be set automatically.)
• TTL

  ---

  This is the number of seconds a domain is cached locally before it expires and is returned to authoritative name servers for updated information. (Will be set automatically.)

What types of DNA exist?

A-Record
The "A" stands for address and is the most commonly used DNS type because it associates a domain name with an Internet address. With an A record, you can forward a domain or subdomain to a specific IPv4 address.

AAAA record
Similar to the A record, the AAAA also forwards to an IP, but this type can only be used for IPv6 addresses.

CNAME record
A "Canonical Name" or CNAME record can be used in place of an A or AAAA record when a domain or subdomain is an alias for another domain. CNAMEs must point to a domain name and cannot include an IP address.

MX record
An MX record (or also called a "Mail Exchange Resource Record") is used exclusively for a domain's e-mail service. It specifies the host name under which the domain's mail server can be reached. Usually, several MX records with different priorities are used for a domain, so that if one mail server fails, another mail server can accept the incoming message.

TXT record
A freely definable text can be stored in a DNS zone in a TXT record. Originally, TXT records were intended to allow administrators to enter human-readable notes in the DNS zone. However, this type is now also used for other purposes, such as preventing e-mail spam (SPF, DKIM, DMARC) or verifying domain ownership. A domain can have a large number of TXT records.

SRV record
With the help of a SRV record (=Service Resource Record) it is specified in a DNS zone which IP-based services are offered by a domain. This type often occurs, for example, if you want to use Microsoft services such as Office365 or SIP services with your domain. An SRV record consists of the service as the source as well as the destination in the form of the priority, weighting, port and the destination server.

CAA record
To protect your own website from misuse, it can be useful to include a CAA entry (="Certificate Authority Authorization") in the DNS settings of your own domain. This DNS type determines which certificate authorities are authorized to issue an SSL certificate for a domain. You can find more information about the CAA record in our FAQ article "What is a CAA record and do I have to use it?".

NS record
This DNS type is used to specify the name servers.