bird 3.2.0 - Malformed AS_PATH attribute - AS_SET segment (1) at 26
Hello all, With Fedora 43's bird 3.2.0-1 rpm installed on an x86_64 system, I'm seeing that several routes are being dropped from a full feed with the log messages below. Using Fedora's bird 3.1.4-1 does not seem to have any issues with the same BGP config and peer. Is this a known bug? What additional information can I provide to aid in the debugging? This is a backup transit connection that is not yet in full production use (but will be soon), so I can help with debugging and testing for now. Cheers, -ben Feb 4 14:42:49 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 14 Feb 4 14:42:49 router bird[24317]: upstream: Invalid route 76.165.0.0/16 withdrawn Feb 4 14:42:49 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 18 Feb 4 14:42:49 router bird[24317]: upstream: Invalid route 204.10.20.0/22 withdrawn Feb 4 14:42:49 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 14 Feb 4 14:42:49 router bird[24317]: upstream: Invalid route 213.186.96.0/19 withdrawn Feb 4 14:42:49 router bird[24317]: upstream: Invalid route 94.178.0.0/15 withdrawn Feb 4 14:42:49 router bird[24317]: upstream: Invalid route 37.52.0.0/14 withdrawn Feb 4 14:42:50 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 26 Feb 4 14:42:50 router bird[24317]: upstream: Invalid route 208.68.112.0/21 withdrawn Feb 4 14:42:50 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 18 Feb 4 14:42:50 router bird[24317]: upstream: Invalid route 147.92.87.0/24 withdrawn Feb 4 14:42:50 router bird[24317]: upstream: Invalid route 52.129.48.0/24 withdrawn Feb 4 14:42:50 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 18 Feb 4 14:42:50 router bird[24317]: upstream: Invalid route 15.20.64.0/18 withdrawn -- "Thought is the essence of where you are now."
Hello Benjamin, On Wed, Feb 04, 2026 at 03:52:27PM -0500, Benjamin LaHaise wrote:
With Fedora 43's bird 3.2.0-1 rpm installed on an x86_64 system, I'm seeing that several routes are being dropped from a full feed with the log messages below. Using Fedora's bird 3.1.4-1 does not seem to have any issues with the same BGP config and peer. Is this a known bug? What additional information can I provide to aid in the debugging? This is a backup transit connection that is not yet in full production use (but will be soon), so I can help with debugging and testing for now.
Feb 4 14:42:49 router bird[24317]: upstream: Malformed AS_PATH attribute - AS_SET segment (1) at 14 Feb 4 14:42:49 router bird[24317]: upstream: Invalid route 76.165.0.0/16 withdrawn
This is a known feature, mandated by RFC 9774, Section 3:
Unless explicitly configured by a network operator to do otherwise (e.g., during a transition phase), BGP speakers:
- MUST NOT advertise BGP UPDATE messages containing AS_SETs or AS_CONFED_SETs and - MUST use the "treat-as-withdraw" error handling behavior per [RFC7606] upon reception of BGP UPDATE messages containing AS_SETs or AS_CONFED_SETs in the AS_PATH or AS4_PATH [RFC6793].Per the above specifications, this document updates [RFC4271] and [RFC5065] by deprecating AS_SET (see [RFC4271], Section 4.3) and AS_CONFED_SET (see [RFC5065], Section 3), respectively.
It is still possible to `allow as sets` explicitly, if you really need to keep them. Maria -- Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
participants (2)
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Benjamin LaHaise -
Maria Matejka