DNS troubleshooting

How to Troubleshoot DNS Errors (Workflow & Tools)

Understand the most common DNS error messages, isolate where the failure happens, and follow a clear sequence using the right diagnostic tools to fix it fast.

Run a DNS lookup

Quick summary

  • Identify whether the issue is local, recursive, or authoritative.
  • Compare answers across resolvers and record types.
  • Check propagation against the previous TTL.
  • Verify nameservers in WHOIS match what's actually serving.

Where DNS errors usually originate

  • Local cache — your OS or browser holds an old answer.
  • Recursive resolver — your ISP or 1.1.1.1 / 8.8.8.8.
  • Authoritative nameserver — where the record is actually published.
  • Registrar — wrong nameservers delegated.

Most common DNS error messages

  • DNS_PROBE_FINISHED_NXDOMAIN — record not found.
  • SERVFAIL — DNSSEC or upstream failure.
  • ERR_NAME_NOT_RESOLVED — same root cause as NXDOMAIN, browser-side.
  • Stale CNAME / wrong A record after migration.

Quick local fixes before deeper diagnostics

  • Flush DNS: ipconfig /flushdns (Windows) or dscacheutil -flushcache (macOS).
  • Switch your resolver to 1.1.1.1 or 8.8.8.8.
  • Test on mobile data to bypass your router.
  • Try a private/incognito browser window.

Troubleshooting workflow

Run through these steps in order. Each step links to the right diagnostic tool.

  1. 1

    Run a DNS lookup

    See A, AAAA, CNAME, MX, NS, and TXT records as published.

    Open DNS Lookup
  2. 2

    Reverse-check the IP

    Confirm the IP resolves back to the expected hostname.

    Open Reverse DNS
  3. 3

    Verify nameservers in WHOIS

    Make sure the registrar points to the right nameservers.

    Open WHOIS Lookup
  4. 4

    Test reachability with ping/traceroute

    Once DNS resolves, confirm the host is actually reachable.

    Open Ping / Traceroute

Recommended next steps

DNS Lookup

Reverse DNS

WHOIS Lookup

HTTP Ping

Traceroute

Fix connection errors

Frequently asked questions

What does DNS_PROBE_FINISHED_NXDOMAIN mean?

The resolver couldn't find an A/AAAA record for that hostname. Either the domain doesn't exist, was just registered, or DNS hasn't propagated yet.

How long does DNS propagation actually take?

Usually 5 minutes to a few hours. The TTL of the previous record sets the maximum delay; resolvers may cache for that long.

Why does the site work on mobile data but not Wi-Fi?

Different resolvers cache different answers, or your router is using a stale or hijacked DNS server. Try 1.1.1.1 or 8.8.8.8.

What's the difference between A, CNAME, and MX records?

A points a name to an IPv4. CNAME aliases one name to another. MX tells the world where to deliver email for that domain.

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