Network Engineering
BGP AS Path Reference
Search BGP AS path concepts — path format, prepending for traffic engineering, private ASN ranges, AS sets in aggregation, and path selection in the BGP decision process.
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About this tool
BGP AS Path Reference
The BGP AS Path Reference covers AS path format, prepending, private ASN ranges, AS set notation, confederation sequences, and AS path's role in BGP route selection.
• Look up AS path prepending syntax before configuring traffic engineering
• Find private ASN ranges that should be stripped before eBGP export
• Understand AS set notation in aggregated route announcements
• Reference AS path selection position in the BGP decision process
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FAQ
What does this tool tell you?
The BGP AS Path Reference covers AS path format, prepending, private ASN ranges, AS set notation, confederation sequences, and AS path's role in BGP route selection.
What affects the result most?
AS path format: space-separated list of ASNs — leftmost is most recently added, rightmost is origin. AS path length: shorter path preferred in BGP route selection (step 6 of decision process). AS path prepending: artificially lengthening path to make route less preferred — traffic engineering.
How should I use the result?
Use this tool to orient quickly to the concepts, field names, or values you are about to look up in a full specification or vendor documentation. It summarizes the common cases; the authoritative source remains whichever standard or vendor doc defines the values themselves.