How DNS Records Affect IPv4 vs IPv6 Availability (and What to Monitor)

DNS is the foundation of every online service — and it directly controls how users reach your site over IPv4 and IPv6. A small mistake in your DNS setup can make your site unreachable for half of your visitors, even if your servers are perfectly fine.

1. A vs AAAA — The Two Critical Records

DNS connects domain names to IP addresses using records:

A record → points to your IPv4 address (e.g., 203.0.113.5)
AAAA record → points to your IPv6 address (e.g., 2001:db8::5)

Both should be configured if your website supports dual-stack (IPv4 + IPv6) connectivity. Missing or outdated records can lead to partial downtime — where users on one protocol can’t reach your site.

2. Common DNS Issues That Break IPv6

Many IPv6 outages come from DNS errors rather than actual server downtime. Typical examples include:

Forgetting to add or update the AAAA record when moving hosts
DNS TTL (Time-To-Live) set too long, delaying record updates
Using separate DNS providers that serve inconsistent data
Misconfigured CNAME or redirect chains that fail for IPv6

3. Why Monitoring DNS Is Essential

Even if your web server is healthy, users first need to resolve your domain to an IP. A failure in that step makes your site look completely down.

UptyBots checks DNS responses during every monitor test — ensuring that your A and AAAA records are both available, valid, and resolve quickly.

4. Detecting Split Uptime Between IPv4 and IPv6

With dual-stack monitoring, UptyBots runs separate checks for both records. This allows you to instantly see if:

IPv4 responds but IPv6 fails (common with expired AAAA records)
IPv6 resolves but connects to the wrong endpoint
DNS servers return inconsistent results from different regions

These insights prevent “hidden outages” that traditional IPv4-only checks often miss.

5. Best Practices for DNS Reliability

Keep both A and AAAA records active and synchronized
Use a reliable, redundant DNS provider with global nodes
Monitor DNS latency and record expiration regularly
Reduce TTL during migrations to speed up propagation

A properly monitored DNS setup ensures your service is reachable over both protocols — everywhere.