[FROG] Optional attribute error peering BGP with BIRD

Donald Sharp sharpd at cumulusnetworks.com
Thu Jul 11 08:54:58 EDT 2019

Derrick -

>From the pcap this looks like FRR is sending an empty NLRI and
according to RFC 2858:

   An UPDATE message that carries no NLRI, other than the one encoded in
   the MP_REACH_NLRI attribute, should not carry the NEXT_HOP attribute.
   If such a message contains the NEXT_HOP attribute, the BGP speaker
   that receives the message should ignore this attribute.

So the enclosed pcap looks correct too me as that we are sending a
default route to our peer to be pointed back at us.


On Thu, Jul 11, 2019 at 7:49 AM Derrick Lim <derrickltl at gmail.com> wrote:
> Hello everyone,
> I’m having an issue with FRR running on Cumulus (4.0+cl3u10), which is
> peering BGP to BIRD (2.0.2, also tried 1.6.3).
> When certain routes from FRR are advertised to BIRD (I configured them
> through vrf leaking on FRR, but not sure if that matters, or its just
> something with the routes), BIRD terminates the BGP session with an
> `Optional attribute error` (on BIRD 2.0.2, different error on 1.6.3)
> when receiving the BGP UPDATE message.
> I’m not sure if this an FRR or BIRD issue, so I'm hoping someone here
> could take a look if the UPDATE message from FRR could possibly be
> malformed, or is BIRD handling this in an odd way.
> I've attached the tcpdump as well as error logs from BIRD, along with
> the bird.conf, as well a portion of the FRR config.
> is the host running BIRD.
> is the host running FRR.
> Regards,
> Derrick
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