prefix in DFZ - AS3.21 / AS196629 - announced with AS_CONFED_SEQUENCE in AS4_PATH - propagated by 35320

Florian Weimer fweimer at bfk.de
Thu Dec 11 08:34:27 UTC 2008

* Andy Davidson:

> OpenBGPd is therefore dropping the sessions when this update is
> received.  Unideal if this attribute is learned on multiple
> upstreams...
> The impact today is fairly limited as there are relatively few bgp
> speakers honouring the 4-byte ASN protocol extension rules, but as
> code that support these features creeps around the internet, the next
> time this happens the impact could be much greater, so we need to
> understand which implementation of which BGP software caused this
> illegal origination.

Uhm, shouldn't you just ignore invalid AS4_PATH attributes, instead of
dropping the session?  It's a transient, optional attribute, so you
can't rely on your peers to filter it.

Florian Weimer                <fweimer at bfk.de>
BFK edv-consulting GmbH       http://www.bfk.de/
Kriegsstraße 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99

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