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In rare scenarios involving large AS paths, there may be a loss of BGP adjacency Technical Level
Symptoms
  • In rare scenarios after upgrade, BGP route is not propogated.

  • On Gaia OS, one of the neighbor routers may complain about malformed message, adjacency is also flapping to down.

  • Similar messages can be seen in neighbor's syslog:

    078794: Sep 19 16:49:10.628 AEST: %BGP-SW1-6-MSGDUMP_LIMIT: unsupported or mal-formatted message received from :
    FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 0042 0200 0000 2840 0101 5040 020E 0203
    0000 FE63 0000 16A3 A300 0022 0E40 0304 0AAD 004E C007 0800 00FE 630A AD00 4E10
    9F2B
    078795: Sep 19 16:49:10.628 AEST: %BGP-SW1-6-MALFORMEDATTR: Malformed attribute in (BGP(0) Prefixes: ) received from ,
    078796: Sep 19 16:49:47.128 AEST: %BGP-SW1-3-NOTIFICATION: sent to neighbor 6/4 (Administrative Reset) 0 bytes
    078797: Sep 19 16:49:47.136 AEST: %BGP-SW1-5-ADJCHANGE: neighbor Down User reset


Cause

The path attributes (of routes sent via BGP) are not being recognized by peer in certain circumstances related to the AS_PATH attribute size.  This can cause the receiving system to reject the route and close the BGP connection, in turn removing BGP routes.


Solution
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