DNS record types cheat sheet

Quick Reference

Most common record

IPv6 record

AAAA

Mail routing

Name alias

CNAME

Text / SPF / DKIM

TXT

Authoritative servers

Tip: DNS record types are case-insensitive. A, a, and a all refer to the same record type. TTL (Time To Live) controls how long resolvers cache a record - lower TTL means faster propagation after changes.

Address Records

Records that map a hostname to an IP address. These are the most fundamental DNS records.

Type	Full name	Maps to	Example value	Use case
`A`	Address	IPv4 address	`192.0.2.1`	Point domain to server IP
`AAAA`	IPv6 Address	IPv6 address	`2001:db8::1`	Point domain to IPv6 server
`CNAME`	Canonical Name	Another hostname	`www.example.com`	Alias - redirect one name to another
`ALIAS`	Alias (ANAME)	Another hostname	`example.com`	Root domain alias (not all providers)

CNAME restriction: A CNAME record cannot coexist with other records for the same name. You cannot use CNAME at the zone apex (root domain like example.com) - only on subdomains like www.example.com.

Mail Records

Records that control email routing and authentication for a domain.

Type	Full name	Purpose	Example value
`MX`	Mail Exchanger	Routes email to mail server	`10 mail.example.com`
`TXT`	Text (SPF)	Defines authorized senders	`v=spf1 include:_spf.google.com ~all`
`TXT`	Text (DKIM)	Email signature verification	`v=DKIM1; k=rsa; p=MIGf...`
`TXT`	Text (DMARC)	Email policy enforcement	`v=DMARC1; p=reject; rua=mailto:...`

MX priority: Lower number = higher priority. 10 mail1.example.com is preferred over 20 mail2.example.com. Multiple MX records provide redundancy.

Infrastructure Records

Records that define the DNS zone structure and infrastructure configuration.

Type	Full name	Purpose	Example value
`NS`	Name Server	Authoritative name servers for zone	`ns1.example.com`
`SOA`	Start of Authority	Zone metadata and primary NS	`ns1.example.com admin.example.com 2024...`
`PTR`	Pointer	Reverse DNS - IP to hostname	`server.example.com`
`SRV`	Service	Service location (port + host)	`10 5 443 server.example.com`
`CAA`	Cert Authority Auth	Which CAs may issue SSL certs	`0 issue "letsencrypt.org"`

All DNS Record Types - Full Reference

Complete reference table of all common DNS record types sorted by category.

Type	Full name	RFC	Description
`A`	Address	RFC 1035	Maps hostname to IPv4 address
`AAAA`	IPv6 Address	RFC 3596	Maps hostname to IPv6 address
`CNAME`	Canonical Name	RFC 1035	Alias from one name to another
`MX`	Mail Exchanger	RFC 1035	Mail server for the domain
`TXT`	Text	RFC 1035	Arbitrary text - SPF, DKIM, DMARC, verification
`NS`	Name Server	RFC 1035	Authoritative name servers for zone
`SOA`	Start of Authority	RFC 1035	Zone metadata, serial, TTL defaults
`PTR`	Pointer	RFC 1035	Reverse DNS - IP address to hostname
`SRV`	Service	RFC 2782	Service port and host location
`CAA`	Cert Authority Auth	RFC 8659	Authorized certificate authorities
`NAPTR`	Naming Authority Pointer	RFC 3403	Rewriting rules - used in VoIP/SIP
`TLSA`	TLS Authentication	RFC 6698	Binds TLS certificate to domain (DANE)
`DS`	Delegation Signer	RFC 4034	DNSSEC - links child zone to parent
`DNSKEY`	DNS Key	RFC 4034	DNSSEC public key for zone
`SSHFP`	SSH Fingerprint	RFC 4255	SSH public key fingerprint
`HINFO`	Host Info	RFC 1035	CPU and OS type (rarely used)

SRV Record Format

SRV records define the location of services. The format is more complex than other record types.

_service._proto.name TTL IN SRV priority weight port target

Field	Description	Example
`_service`	Service name (e.g. _https, _sip)	`_https`
`_proto`	Protocol (_tcp or _udp)	`_tcp`
`priority`	Lower = higher priority	`10`
`weight`	Load balancing weight	`5`
`port`	TCP/UDP port number	`443`
`target`	Target hostname	`server.example.com`

Real example: _sip._tcp.example.com 3600 IN SRV 10 5 5060 sip.example.com - routes SIP traffic to port 5060.

Frequently Asked Questions

What is the difference between A and CNAME records?

An A record maps a hostname directly to an IPv4 address. A CNAME record is an alias that maps one hostname to another hostname. CNAMEs are useful for subdomains that should follow the same IP as the root domain, but they cannot be used at the zone apex (root domain).

Why can't I use a CNAME at the root domain?

The DNS specification (RFC 1034 §3.6.2, clarified by RFC 2181 §10.1) prohibits CNAME records from coexisting with other record types at the same name. Since the zone apex always has at least SOA and NS records, a CNAME is not allowed there. Use ALIAS or ANAME records (provider-specific) or an A record instead.

What is TTL and what value should I use?

TTL (Time To Live) is measured in seconds and controls how long DNS resolvers cache a record. Use lower values (300-900 seconds) before planned changes, and higher values (3600-86400 seconds) for stable records to reduce DNS lookup overhead. Common values: 300 (5 min), 3600 (1 hour), 86400 (24 hours).

How do I verify a DNS record was applied?

Use nslookup example.com, dig example.com A, or Resolve-DnsName example.com in PowerShell. Online tools like MXToolbox or Google Admin Toolbox also show current DNS records. Remember that propagation can take up to the TTL value of the previous record.

What is reverse DNS and when do I need it?

Reverse DNS (PTR records) maps an IP address back to a hostname. It is primarily used by mail servers to verify sender identity - many spam filters reject mail from IPs without a matching PTR record. Reverse DNS is managed by your IP address provider, not your domain registrar.

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