DNS & DOMAINS
DNS records provide structured information used by the Domain Name System. Depending on the record type, they can map names to addresses, identify mail servers, create aliases, publish verification information, or describe network services.
A domain can contain many records of different types, and DNS providers may present those records differently in their management interfaces.
Common DNS Record Types
| Type | Purpose | Typical Data |
|---|---|---|
A |
Maps a hostname to an IPv4 address. | IPv4 address |
AAAA |
Maps a hostname to an IPv6 address. | IPv6 address |
CNAME |
Creates an alias pointing to another hostname. | Target hostname |
MX |
Identifies mail servers responsible for a domain. | Priority and hostname |
TXT |
Stores text associated with a DNS name, often used for verification or policy data. | Text string |
NS |
Identifies authoritative name servers for a DNS zone. | Name server hostname |
SOA |
Contains administrative information about a DNS zone. | Zone metadata |
PTR |
Provides reverse DNS mapping from an IP address to a hostname. | Hostname |
SRV |
Describes the location of certain network services. | Priority, weight, port, target |
CAA |
Specifies which certificate authorities may issue certificates for a domain. | Issuer policy data |
DNSKEY |
Publishes DNSSEC public key material. | DNSSEC key data |
DS |
Connects DNSSEC information between a parent and child zone. | Key tag, algorithm, digest |
Important DNS Concepts
- TTL: Determines how long a DNS response may remain cached before it needs to be queried again.
- Authoritative server: A DNS server that holds authoritative information for a zone.
- Recursive resolver: A DNS service that queries other DNS servers on behalf of clients.
- Reverse DNS: DNS resolution that maps an IP address back toward a hostname, commonly using PTR records.
- DNSSEC: A collection of mechanisms that allow DNS data to be authenticated using cryptographic signatures.
A Record vs CNAME
An A record directly supplies an IPv4 address. A CNAME instead aliases one hostname to another hostname. This distinction matters because the resolver follows the hostname relationship rather than receiving an IPv4 address directly from the CNAME record.