DNS Records Explained: Types, Purpose, and Failure Scenarios

#dns

DNS (Domain Name System) is the layer that connects human-readable domains (like example.com) to actual services such as web servers, mail servers, or CDNs. Every domain relies on different types of DNS records, and missing even a single one can lead to website outages or email failures.

This article explains the main DNS record types, why each one matters, and which mistakes are commonly made when setting them up or migrating between providers.

Common DNS Record Types

Record Type	Purpose	Example	What Happens If Missing
A	Maps a domain to an IPv4 address	`example.com → 123.45.67.89`	Website will not load
AAAA	Maps a domain to an IPv6 address	`example.com → 2606:4700::abcd`	IPv6 users may not reach the site
CNAME	Makes one domain an alias of another	`www.example.com → example.com`	Aliases or subdomains may stop working
MX	Specifies which server handles incoming email	`example.com → aspmx.l.google.com`	Email sending and receiving will fail
TXT	Stores text data like SPF, DKIM, or verification tokens	`v=spf1 include:_spf.google.com ~all`	Emails may get rejected or marked as spam
NS	Tells the internet which DNS provider is authoritative for the domain	`ns1.dnsprovider.com`, `ns2.dnsprovider.com`	The entire domain becomes unreachable because no DNS server is responsible for it
SOA	Technical details about the DNS zone — includes primary nameserver and zone metadata	Usually auto-generated by the DNS provider	DNS may not function properly; most providers enforce SOA automatically so you rarely configure this manually

Most Error-Prone Situations

1. Migrating Between DNS Providers

When switching DNS from one provider to another (e.g., Namecheap → Route53), the new provider must contain every record from the previous provider before switching nameservers.

Missing records commonly include:

Root A record (example.com)
CNAME for www.example.com
MX, SPF, or DKIM TXT records (causing email delivery failures)
Wildcard records (e.g. *.example.com)

2. Forgetting the Root Domain

It’s common to configure subdomains like api.example.com or app.example.com but forget to add a record for the root domain itself (example.com). Many users type only the base domain, so the root must always have an A or redirect record.

3. Incorrect TTL Values

TTL (Time To Live) controls how long DNS records are cached.

High TTL during testing or migration causes delays in propagation.
Low TTL in production may cause unnecessary DNS lookups and latency.

A good practice is:

Stage	Recommended TTL
Migration / Testing	30–300 seconds
Stable Production	300–3600 seconds

How to Verify DNS Correctness

Use tools like:

dig example.com
dig NS example.com
dig MX example.com

Or online tools:

Verification checklist:

✔ Root domain resolves
✔ www resolves if used
✔ Subdomains resolve
✔ Email (MX/TXT) records are intact
✔ Nameservers match the intended DNS provider

Conclusion

DNS configuration may seem straightforward, but it is highly sensitive. Each record type serves a specific purpose, and overlooking even one can disrupt website access, email services, or third-party integrations.

Before switching nameservers or making DNS changes:

Export all records
Recreate them carefully
Verify using DNS lookup tools
Only then apply changes

A proper DNS setup is invisible when correct and immediately noticeable when wrong.

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