Types of DNS Records and Their Purpose (AZ-104)

A

Maps a domain name to an IPv4 address.

example.com → 20.10.1.5

AAAA

Maps a domain name to an IPv6 address.

example.com → 2001:db8::1

CNAME

Maps an alias to another domain name.

www.example.com → example.azurewebsites.net

MX

Specifies the mail server responsible for receiving email.

example.com → mail.example.com

TXT

Stores text values for domain verification, SPF, and other purposes.

example.com → "v=spf1 ..."

NS

Identifies the authoritative name servers for a DNS zone.

example.com → ns1-01.azure-dns.com

SOA

Stores DNS zone authority and administrative information.

Primary name server and zone serial number

PTR

Maps an IP address to a domain name (reverse DNS).

20.10.1.5 → server.example.com

SRV

Specifies the hostname and port for a particular service.

_sip._tcp.example.com → server:5060

CAA

Specifies which certificate authorities may issue TLS certificates for a domain.

example.com → letsencrypt.org

DS

Stores delegation information used to establish DNSSEC trust between parent and child zones.

Parent zone references a child's DNSSEC key digest.

DNSKEY

Publishes a public key used by DNSSEC to validate signed DNS data.

Public signing key for a DNS zone

RRSIG

Contains a DNSSEC digital signature for a DNS record set.

Signature used to validate DNS responses

NSEC / NSEC3

Provides DNSSEC proof that a DNS name or record does not exist.

Authenticated proof of nonexistence

Azure DNS

Hosts DNS zones and resolves domain names using standard DNS records.

Public DNS Zone

Hosts records used to resolve domain names on the public internet.

Private DNS Zone

Resolves domain names within linked Azure virtual networks.

A Record vs CNAME

A points to an IPv4 address; CNAME points to another domain name.

CNAME Restriction

A CNAME cannot coexist with other record types at the same name, and it cannot be used at a zone apex.

TTL (Time to Live)

Determines how long DNS resolvers may cache a record.

Alias Record

An Azure DNS feature that points a supported record set to an Azure resource, such as a public IP address.

Reverse Lookup

Uses PTR records to map an IP address back to a hostname.