Common DNS Record Types

A DNS zone stores different kinds of resource records, each mapping a name to a specific piece of information. The record type tells you what kind of answer it provides.

The exam expects you to recognize the most common types and what each does. This lesson covers the essentials.

The A record (Address record) maps a domain name to an IPv4 address. It is the most common record and the one most lookups ultimately seek.

For example, an A record might map example.com to 93.184.216.34. When you browse to a name, an A record usually supplies the IPv4 address you connect to.

The AAAA record (quad-A) maps a name to an IPv6 address. It plays the same role as an A record but for the newer 128-bit addresses.

Dual-stack hosts publish both A and AAAA records so clients can connect over whichever protocol they support. The four As hint at IPv6’s four-times-larger address size.

The CNAME record (Canonical Name) creates an alias, pointing one name to another name rather than an address. For example, www.example.com might be a CNAME for example.com.

This lets several names share one target, so updating the underlying address in one place updates them all. A CNAME points to a name, never directly to an IP.

The MX record (Mail Exchanger) specifies the mail servers that accept email for a domain. It includes a priority value so backups can be tried in order.

When someone emails you@example.com, the sending server looks up example.com’s MX records to find where to deliver the mail.

The NS record (Name Server) lists the authoritative name servers for a domain. These are the servers that hold the domain’s records.

NS records are how delegation works: a parent zone uses NS records to point to the servers responsible for a child zone, building the DNS hierarchy.

The PTR record (Pointer) does the reverse of an A record, mapping an IP address back to a name. This is reverse DNS.

PTR records are used in email anti-spam checks and logging, where a server wants to confirm the name behind an address. They live in a special reverse-lookup zone.

The TXT record holds arbitrary text. Today it is widely used for email security and verification, such as SPF, DKIM, and domain-ownership proofs.

For example, an SPF TXT record lists which servers may send mail for a domain, helping receivers detect spoofed email. TXT records are flexible and increasingly important.

The SOA record (Start of Authority) sits at the top of every zone and holds administrative details: the primary name server, contact email, and timers like refresh and the default TTL.

Each zone has exactly one SOA. It defines the zone’s authority and governs how secondary servers stay in sync.

The SRV record (Service) locates the server and port for a specific service, such as VoIP or directory logins. It includes priority, weight, port, and target host.

SRV records let clients automatically discover where a service lives instead of hard-coding a server name and port, and they are heavily used by Active Directory.

Summarize the key records:

• A = name to IPv4; AAAA = name to IPv6
• CNAME = alias to another name
• MX = mail servers; NS = name servers
• PTR = IP to name (reverse); TXT = text/verification

Knowing these covers the vast majority of exam questions.

Match the need to the record.

You learned the common DNS record types.

• A maps a name to IPv4; AAAA maps to IPv6.
• CNAME is an alias to another name (never an IP).
• MX names mail servers; NS names authoritative servers.
• PTR does reverse (IP to name); TXT holds text like SPF/DKIM.
• SOA sits atop each zone with admin and timing details.