DNS Record Types

DNS records are entries in a zone file that map domain names to various kinds of data. Each record has a type, a name, a value, and a TTL (time-to-live).

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A Record (Address)

Property	Value
Maps	Domain → IPv4 address
Example	piyushgarg.dev → 1.2.3.4
Use case	Direct IP resolution for a domain or subdomain

The A record is the most commonly used DNS record. It directly resolves a hostname to an IPv4 address. When a browser queries a domain, the authoritative server typically returns an A record (or a CNAME that eventually resolves to one).

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CNAME Record (Canonical Name / Alias)

Property	Value
Maps	Domain → another domain
Example	magic.piyushgarg.xyz → google.com
Use case	Creating aliases that follow the target’s IP dynamically

How CNAME Resolution Works

magic.piyushgarg.xyz  → CNAME → google.com  → A record → 5.6.7.8

1. Client asks for magic.piyushgarg.xyz.
2. DNS returns a CNAME pointing to google.com.
3. Client makes another DNS query for google.com.
4. google.com’s A record returns 5.6.7.8.
5. Both domains effectively resolve to the same IP.

Why Use CNAME?

Scenario	Benefit
Outsourcing to Vercel / Cloudflare / CDN	Provider changes IP → your alias follows automatically
Multiple subdomains pointing to same service	Update target once, all aliases follow
Avoid hardcoding IPs	Dynamic resolution; no 2-AM outage when provider migrates

“If Vercel changes their IP at 2 AM, your CNAME follows it automatically. If you hardcoded an A record, your site is down until you wake up.” — Day 30 CKA Video

Restrictions

• A CNAME cannot coexist with other records on the same name (e.g., you can’t have both a CNAME and an MX record for mail.example.com).
• The root/apex domain (e.g., example.com) typically cannot have a CNAME (DNS RFC restriction); use an ALIAS or ANAME record at the apex if your provider supports it.

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MX Record (Mail Exchange)

Property	Value
Maps	Domain → mail server(s)
Example	somecompany.com → mail.somecompany.com (priority 10)
Use case	Receiving email for a custom domain

MX records tell mail transfer agents (MTAs) where to deliver email for a domain. They include a priority value (lower = preferred). Multiple MX records provide failover.

Used when setting up:

• Google Workspace (G Suite)
• Microsoft 365
• Self-hosted mail servers

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NS Record (Name Server)

Property	Value
Maps	Subdomain → authoritative DNS server
Example	abc.piyushgarg.xyz → ns.something.com
Use case	Delegating a subdomain to a different DNS provider or self-hosted DNS

How NS Delegation Works

1. Parent zone (piyushgarg.xyz) has an NS record: abc.piyushgarg.xyz → ns.something.com.
2. Any query for *.abc.piyushgarg.xyz is forwarded to ns.something.com.
3. ns.something.com runs a DNS server on UDP port 53 and responds with the final IP.

“If you want to build your own DNS server, you run a machine with port 53 open and tell your users to add an NS record pointing to you.” — Day 30 CKA Video

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TXT Record (Text)

Property	Value
Maps	Domain → arbitrary text string
Example	example.com → "v=spf1 include:_spf.google.com ~all"
Use case	Domain verification, SPF, DKIM, DMARC, arbitrary metadata

TXT records are human-readable text entries. Common uses:

• Domain ownership verification (Google Search Console, SSL providers)
• SPF records — specify which mail servers can send email for the domain
• DKIM / DMARC — email authentication and anti-spoofing

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SRV Record (Service)

Property	Value
Maps	Service + protocol → hostname + port
Example	_sip._tcp.example.com → sipserver.example.com:5060
Use case	Service discovery (SIP, XMPP, LDAP, etc.)

Less commonly used for web traffic, but important for VoIP, messaging, and internal service discovery.

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Record Type Summary

Record	Maps To	Typical Use
A	IPv4 address	Direct domain → IP
CNAME	Another domain	Aliases, outsourcing, CDNs
MX	Mail server	Custom email hosting
NS	DNS server	Subdomain delegation
TXT	Text string	Verification, SPF, DKIM
SRV	Host:port	Service discovery

Source

• 40 — What Is DNS With @piyushgargdev