A step-by-step DNS troubleshooting checklist for domains, websites, email, nameservers, SSL and propagation checks.

Quick wins from this guide
  • Follow a repeatable process
  • Avoid checking the wrong DNS zone
  • Know when the issue is not DNS

1. Confirm the exact hostname

Check whether the problem affects the root domain, www, a subdomain, mail or another hostname. example.com and www.example.com can have different records and different problems.

2. Confirm authoritative nameservers

Before editing records, confirm which nameservers are authoritative. If the registrar points to nameservers at one provider but you are editing records somewhere else, nothing will change publicly.

3. Check the relevant record

For websites, check A, AAAA and CNAME records. For email, check MX and TXT records. For SSL issuance, check A/AAAA and CAA records. For reverse DNS, check PTR with the IP provider.

4. Compare public resolvers

Compare results from multiple resolvers if you suspect caching. Use DNSNow for a quick check and command line examples such as dig @1.1.1.1 example.com A and dig @8.8.8.8 example.com A.

5. Move beyond DNS

If DNS is correct, check the web server, SSL certificate, redirects, firewall rules, application logs and hosting configuration. For more terminal practice, use the Linux Troubleshooting Hub on CommandLineQuiz.

Quick commands to try

dig example.com A
dig example.com MX +short
host -t TXT example.com

Practise the command line side

DNSNow gives you quick web checks. For hands-on Linux command practice, use CommandLineQuiz dig Command Builder, the Linux Troubleshooting Hub and the Bash Scripting Hub.

FAQs

What should I check first in DNS?

Start with the exact hostname and authoritative nameservers, then check the record type relevant to the issue.

How do I know if I edited the wrong DNS zone?

Compare public NS records with the DNS provider you edited. If they do not match, you probably changed a zone that is not authoritative.

When is the problem not DNS?

If records resolve correctly to the expected destination, the issue may be web server, SSL, firewall, application or mail server configuration.

Sources and further reading