Reverse lookups
11IPv4 reverse lookup uses an ordinary DNS question in the IN-ADDR.ARPA tree.
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Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
DIAGRAM§ 5.2.1 ↗
RFC 1034 · § 5.2.1EXAMPLE
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Return naming information.
Treat this as DNS data rather than authentication.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
Reverse the address labels, then query PTR.
- The reverse name for 192.0.2.20 is 20.2.0.192.in-addr.arpa.
- Reverse DNS uses standard PTR queries, not the historic optional inverse-query opcode.
- A reverse answer does not by itself prove who controls a connection or that forward and reverse mappings agree.
This RFC predates IPv6 reverse lookup. The example uses a documentation-only IPv4 address.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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