practice task

Separate DNS Failure From Server Failure

Users say a site is down, but the server may still be answering. You need to compare public DNS with a forced request to the expected IP.

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Try first

dig +short example.com && curl -I https://example.com/

Goal

Confirm whether the hostname resolution path or the web server response path is failing.

Expected output

DNS should return the public address currently used by clients, and curl should return HTTP headers. A forced --resolve request can prove the target server answers even when DNS points elsewhere.

Teaches

Test name resolution and direct server response separately. A healthy server can still be unreachable through bad DNS.

Common mistake

Treating one successful curl from the server itself as proof that public DNS and external routing are correct.

command set

Commands to know

dig +short example.com
curl -I https://example.com/
curl --resolve example.com:443:203.0.113.10 -I https://example.com/

Watch this command run

Example output from a temporary Linux lab

command replay example output

Your Site Is Not Down. DNS Might Be Lying.

Review the related command card and compare your expected output with the command replay.

Watch command run