DNS Records

Record Types

A (Address Record) - Maps a domain to an IPv4 address.

• Key Note: This is the most common DNS record for resolving domain names to IPv4 addresses.

example.com. IN A 93.184.216.34

AAAA (IPv6 Address Record) - Maps a domain to an IPv6 address.

• Key Note: Works like an A record but for IPv6 addresses.

example.com. IN AAAA 2606:2800:220:1:248:1893:25c8:1946

CNAME (Canonical Name Record) - Aliases one domain to another (i.e., maps a subdomain to a primary domain).

• Key Note: Used when you want multiple domain names to point to the same destination.

www.example.com. IN CNAME example.com.

MX (Mail Exchange Record) - Specifies mail servers for a domain.

• Key Note: Has a priority number, where a lower value means higher priority.

example.com. IN MX 10 mail1.example.com.

SOA (Start of Authority Record) - Contains administrative information about the domain.

• Key Details:
  • Primary Name Server: Specifies the authoritative DNS server.
  • Admin Email: Contact email for DNS administrator.
  • Serial Number: Helps secondary servers determine updates.
  • Refresh/Retry/Expire/Min TTL: Defines update and cache settings.

example.com. IN SOA ns1.example.com admin.example.com

PTR (Pointer Record) - Reverse DNS lookup (maps an IP address back to a domain).

• Key Note: Used in reverse DNS for verifying email servers.

34.216.184.93.in-addr.arpa. IN PTR example.com.

TXT (Text Record) - Stores text-based information, often for security and verification.

• Key Note: Commonly used for SPF, DKIM, DMARC and domain verification.

example.com. IN TXT "v=spf1 include:_spf.google.com ~all"

NS (Name Server Record) - Specifies authoritative name servers for a domain.

• Key Note: Indicates which DNS servers store the domain’s records.

example.com. IN NS ns1.exampledns.com.

SRV (Service Record) - Specifies services and their locations (used for VoIP, SIP, LDAP).

• Key Details:
  • Priority: Determines order of preference.
  • Weight: Load balancing between servers.
  • Port: Defines the service port.

_sip._tcp.example.com. IN SRV 10 60 5060 sipserver.example.com.

CAA (Certificate Authority Authorization Record) - Specifies which Certificate Authorities (CAs) can issue SSL/TLS certificates.

• Key Note: Helps prevent unauthorized SSL certificate issuance.

example.com. IN CAA 0 issue "letsencrypt.org"

SPF (Sender Policy Framework Record) - Specifies authorized mail servers for a domain.

• Key Note: Stored in TXT records, prevents email spoofing.

example.com. IN TXT "v=spf1 ip4:192.168.0.1/16 -all"

NAPTR (Naming Authority Pointer Record) - Used for advanced redirection and service discovery (e.g., VoIP).

• Key Details:
  • Order & Preference: Define priority.
  • Flags: Determine how records are interpreted.
  • Service & Regex: Define redirection behavior.

example.com. IN NAPTR 100 10 "u" "E2U+sip" "!^.*$!sip:info@example.com!" .

Final Notes

✅ Core Records: A, AAAA, CNAME, MX, SOA, PTR, TXT, NS ✅ Specialized Records: SRV, CAA, SPF, NAPTR ✅ Security Use: CAA, SPF, TXT (DKIM, DMARC) ✅ Email Handling: MX, SPF, PTR

Check out the link to my original notes below. It was important to me to break down and understand the examples of each record.