DNS Troubleshooting: A Step-by-Step Guide for Website Owners

DNS problems are uniquely frustrating because they're often intermittent, invisible from your own device (thanks to local caching), and can make a perfectly healthy server look completely down to the outside world. If your site is unreachable and you've ruled out the server itself, DNS is usually the next place to look. Here's a systematic way to work through it.

Understand Why DNS Issues Are So Confusing

DNS records propagate across the internet gradually and get cached at multiple layers — your ISP, your operating system, your browser, and various DNS resolvers around the world. This means a DNS problem can look completely different depending on who's checking: your site might be perfectly reachable from your office (cached) while being totally broken for visitors in another region (not cached, or resolving to outdated records).

Step 1: Verify the Actual DNS Records

Start by checking what your DNS records currently say, using a tool that queries authoritative servers directly rather than relying on cached results:

dig yourdomain.com A
dig yourdomain.com NS
dig yourdomain.com CNAME

Confirm the A record points to the correct IP address, and that NS records point to the correct nameservers. A surprising number of "my site is down" incidents trace back to someone editing the wrong record, or a domain registrar reverting nameservers during an unrelated change.

Step 2: Check From Multiple Locations

Because of caching and propagation delays, always verify DNS resolution from multiple geographic locations, not just your own device. Tools like whatsmydns.net show you how your domain resolves from dozens of locations worldwide simultaneously — this quickly reveals whether you have a genuine record problem or just a local caching/propagation delay.

Step 3: Confirm TTL Values Aren't Working Against You

Time To Live (TTL) determines how long DNS resolvers cache a record before re-checking it. If your TTL is set to 24 hours and you just changed an A record, don't expect the change to be visible everywhere immediately — some resolvers will keep serving the old value until their cache expires.

For planned changes (like a server migration), lower your TTL to something short (like 300 seconds) a day or two in advance. This way, when you actually make the change, it propagates quickly instead of taking up to a full day.

Step 4: Check for Expired Domain Registration

It sounds obvious, but domain expiration is a surprisingly common cause of sudden "DNS failures" — the domain simply stopped resolving because the registration lapsed. Check your registrar account directly rather than assuming this isn't the issue.

Step 5: Verify Nameserver Configuration

If you recently moved hosting providers or DNS management services, confirm your domain's nameservers actually point to the correct provider. A common mistake is updating DNS records in one place (say, your new host's DNS panel) while your domain's registrar still points to the old nameservers entirely — meaning your changes have no effect at all.

Step 6: Check for DNSSEC Misconfiguration

If DNSSEC is enabled and misconfigured (for example, after a nameserver change without updating DS records at the registrar), some resolvers will refuse to resolve your domain entirely as a security precaution, even though the underlying records are technically fine. This is a less common issue but a particularly confusing one when it happens, since the failure mode looks like general DNS breakage.

Monitor DNS Continuously

DNS issues don't always announce themselves clearly — sometimes it's a partial failure (some resolvers work, others don't) that looks like intermittent flakiness rather than an outright outage. Ongoing DNS monitoring that checks resolution from multiple locations on a schedule catches these gradual or partial failures much faster than waiting for user reports.

The Bottom Line

Most DNS problems come down to one of a handful of causes: an incorrect record, a propagation delay, an expired domain, or a nameserver mismatch. Working through them in order — records, propagation, registration, nameservers — will resolve the vast majority of DNS incidents without needing to guess.