Explain an unreachable destination
03Type 3 reports reasons such as unreachable networks, hosts, protocols, or ports.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
RFC 792 · Destination Unreachable MessageEXAMPLE
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03
Quote the original header and data prefix so the sender can identify the traffic.
Quote the original header and data prefix so the sender can identify the traffic.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
The code qualifies the failure; not all unreachable conditions have the same meaning.
- The code qualifies the failure; not all unreachable conditions have the same meaning.
- The original error includes the IP header and at least the first 64 data bits of the triggering datagram.
The drawing is a simplified worked example. Follow the linked RFC and its updates for implementation requirements.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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