Glossary
DNS
SERVFAIL
A DNS response code meaning the server could not produce a valid answer. A validating resolver returns it when DNSSEC validation fails, which is why a signing mistake looks like a total outage rather than a warning.
Defined in RFC 1035 §4.1.1.
Where this appears
The lessons that use this term, and what each is for.
Domain Security FundamentalsHow DNSSEC breaks in productionDiagnose a SERVFAIL caused by DNSSEC and name the specific failure.DNS Security PractitionerSignatures expireExplain why a zone that was valid yesterday fails today with no change made to it.Domain Security PractitionerA broken chain you cannot fixDecide what to do about a DNSSEC failure in a zone somebody else operates.