Use AS paths to detect loops
03AS_PATH records autonomous-system traversal information and supports loop detection.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
DIAGRAM§ 5.1.2 ↗
RFC 4271 · § 5.1.2EXAMPLE
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03
Exclude the looping candidate rather than forwarding around the loop.
Exclude the looping candidate rather than forwarding around the loop.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
RFC 1771RFC 4271 Appendix A
The revision explicitly allows multiple instances of the local AS in AS_PATH for inter-AS traffic engineering and clarifies tie breaking.
Read the updated RFC section ↗A speaker generally rejects a route containing its own AS as specified by the decision process.
- A speaker generally rejects a route containing its own AS as specified by the decision process.
- Prepending one’s own AS more than once can influence other systems’ path preferences; it does not authenticate the path.
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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