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DNS troubleshooting: a structured approach

2026-09-20 · A generalised guide to investigating hostname resolution failures.

A device may reach an IP address but fail to reach the corresponding hostname. That is one clue, not proof of a DNS issue.

First checks

1. Confirm the scope: one device, one service or multiple users?
2. Verify the current IP address, default gateway and configured DNS servers.
3. Compare name resolution using the configured resolver and an appropriate known-good resolver.
4. Check whether the service is reachable by IP and whether firewall, proxy or application settings affect the result.
5. Verify any recent DNS record or server changes with the responsible team.

Example commands

On Windows:

ipconfig /all
nslookup example.com
Resolve-DnsName example.com
Test-NetConnection example.com -Port 443

Use the correct internal hostname only in an authorised environment. Avoid publishing private infrastructure identifiers. This article is a general learning note, not an employer incident report.