AS_PATH Parser
Parse BGP AS_PATH text, flag legacy set segments deprecated by RFC 9774, and calculate its decision-process path length.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
Summary
How it works
Parses bare ASNs as AS_SEQUENCE, braces as AS_SET, parentheses as AS_CONFED_SEQUENCE, and square brackets as AS_CONFED_SET. RFC 9774 deprecates AS_SET and AS_CONFED_SET: unless explicitly configured otherwise for a transition, BGP speakers must not advertise UPDATEs containing these segments and must apply treat-as-withdraw when receiving them in AS_PATH or AS4_PATH. This offline parser still accepts and marks the set forms so historical dumps can be inspected; parsing them does not mean they are recommended or normally permitted in modern BGP operation. For decision-process length, each AS_SEQUENCE member counts once, each AS_SET counts once, and confederation segments do not count outside their confederation. A final AS_SET has multiple possible origin ASNs, so none is selected as uniquely authoritative. Repeated ASNs are highlighted as possible loops; this is structural inspection, not a live route verdict.