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Concepts

Domain Name / Domain

See Domains.

DNS

The Domain Name System is a name management system for computing devices connected to a network, be it public (Internet) or private. It translates text-based domain names to numerical IP addresses.

DNS Delegation

DNS delegation is when a DNS Name Server delegates authority over a part of its namespace to one or more other DNS servers. Delegation can be seen as a pointer to the authoritative name servers for a subdomain. With Dedibox, this can be useful if you want to edit the reverse of IPv4/27 blocks and the IPv6 blocks (/48 - /56 - /64), as that can’t be done directly in the console, but can be achieved by delegating those subnets to your name servers, who will then take on the task of propagating the DNS reverses of your IPs on the Internet.

DNS Name Servers

A DNS Name Server stores the DNS Records for a given domain(s).

DNS Record

A DNS Record holds information translating a domain or subdomain to an IP address, mail server or other domain/subdomain. DNS records for each DNS Zone are stored within files called DNS Zone Files. These are hosted on DNS Name Servers. DNS records act as instructions for the DNS servers, so they know which domain names and IP addresses are associated with each other. DNS records can be of multiple types, called Resource Records.

DNS Zone

A DNS zone hosts the DNS records for a distinct part of the global domain namespace, and is managed by a specific organization or administrator.

DNS Zone File

A DNS Zone File describes a DNS Zone, containing DNS records which constitute mappings between domain names, IP addresses and other resources.

DNS Namespace

DNS domains are all organized in a hierarchy called the DNS namespace. The hierarchy consists of:

  • Top Level Domains: .com or .net, for example.
  • Second-level domains: example.com
  • Subdomains: mysite.example.com or sub.domain.example.com.

IP Address

An Internet Protocol address is a unique address that identifies a device on the internet or a local network. Generally, when we talk about IP addresses, we are referring to IPv4 addresses. However, due to the global shortage of IPv4 addresses, IPv6 addresses have also been in deployment since the mid-2000s.

Resource Records

Information in DNS zones is categorized and organized through a list of DNS record types, called Resource Records (RRs). Each of these records has a type, an expiration time (Time to Live - TTL), a name, and type-specific data for certain types of records.

The most common records are:

  • A record: Address record, it is mostly used to map domain names to the IPv4 address of a specific server
  • AAAA record: IPv6 Address record, it returns an IPv6 address and is mostly used to map domain names to the IPv6 address of a specific server.
  • CNAME record: Canonical name record, an alias of one name to another. The DNS lookup will continue by looking up the new name.
  • MX record: Mail exchange record, it maps a domain name to a list of one or several mail servers for that domain.
  • TXT record: Text record, it is often used to carry machine-readable data such as information for automated domain validation.

Reverse DNS

Reverse DNS, or rDNS, is exactly the opposite of classic forward DNS as we know it. Forward DNS maps a hostname to an IP address. Reverse DNS means we are mapping the IP address to a hostname. This can be very useful, especially if you want to send emails from your server.

Root Server

Root Servers are a type of DNS Name Server pertaining to Top Level domains. They are the first step in the resolution of any domain name, since they contain information about the authoritative DNS servers for each Top Level Domain.

Secondary DNS

Secondary DNS uses zone transfer to automatically transfer DNS zones from a primary DNS server to a secondary DNS server. The secondary server is useful for redundancy, resiliency and load balancing. The zone files on a secondary DNS server are read-only copies of the files on the primary server, and are automatically updated if a file changes on the primary server.