DNS Record Types

Also Known As

TL;DR

Explanation

Key record types: A (domain → IPv4 address), AAAA (domain → IPv6 address), CNAME (alias → another domain name, cannot coexist with other records at apex), MX (mail server + priority), TXT (arbitrary text — SPF, DKIM, domain verification), SRV (service location with port and protocol), NS (authoritative nameservers), SOA (zone authority), CAA (which CAs may issue certificates). ALIAS/ANAME records (provider-specific) solve the CNAME-at-apex limitation for load balancers. TTL controls caching duration.

Diagram

flowchart TD
    DOMAIN[example.com] --> TYPES{DNS Record Types}
    TYPES -->|A| A_REC[A Record<br/>domain to IPv4<br/>93.184.216.34]
    TYPES -->|AAAA| AAAA_REC[AAAA Record<br/>domain to IPv6]
    TYPES -->|CNAME| CNAME_REC[CNAME<br/>alias to another domain<br/>NOT at apex]
    TYPES -->|MX| MX_REC[MX Record<br/>mail server + priority]
    TYPES -->|TXT| TXT_REC[TXT Record<br/>SPF DKIM verification]
    TYPES -->|NS| NS_REC[NS Record<br/>authoritative nameservers]
    subgraph Common_Mistakes
        APEX[CNAME at apex invalid<br/>use ALIAS or A record]
        MX_C[MX pointing to CNAME<br/>RFC violation]
    end
style A_REC fill:#238636,color:#fff
style MX_REC fill:#1f6feb,color:#fff
style TXT_REC fill:#d29922,color:#fff
style APEX fill:#f85149,color:#fff

Common Misconception

Why It Matters

Common Mistakes

• CNAME at the apex — use ALIAS/ANAME or A records for the root domain.
• MX record pointing to a CNAME — MX must point directly to an A record, not a CNAME.
• Forgetting CAA records — without CAA, any CA can issue certificates for your domain.
• TTL too high before a planned change — set TTL to 300 (5 min) days before the change, not minutes before.

Code Examples

# Invalid CNAME at apex — breaks entire domain:
example.com.    IN CNAME   myapp.elb.amazonaws.com.
# This is invalid — CNAME at apex prevents SOA and NS records
# Result: entire domain stops resolving

# MX pointing to CNAME — RFC violation:
example.com.    IN MX 10   mail.example.com.
mail.example.com. IN CNAME alias.mailprovider.com.  # Invalid!

# Correct record usage:
# Apex: use A record or ALIAS (Route 53):
example.com.    IN ALIAS   myapp.elb.amazonaws.com.  # Route 53 ALIAS

# Subdomain: CNAME is fine:
www.example.com. IN CNAME  myapp.elb.amazonaws.com.

# MX with direct A record:
example.com.    IN MX 10   mail.sendgrid.net.  # Points directly, no CNAME chain

# TXT for SPF + domain verification:
example.com.    IN TXT 'v=spf1 include:sendgrid.net ~all'
example.com.    IN TXT 'google-site-verification=abc123'

References

• ↗ https://www.cloudflare.com/learning/dns/dns-records/

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