Question about AS Origin changes

Florian Weimer fweimer at
Fri Mar 25 08:53:16 CDT 2011

* Yaoqing Liu:

> I am wondering if anyone can give me possible reasons for some uncommon BGP
> origin change activity.  What we see is that sometimes the origin for a
> prefix seems to change from a customer AS to it upstream provider and back.
>  In many instances the prefix simply switches back and forth for hours or
> even days and sometimes very rapidly .  Below I’m including an example of
> some of the activities I see.

This is expected if the upstream has a static route for the prefix (or
a route which redistributed from another routing protocol).  This
could be a leftover from a non-BGP setup with the customer.  Or this
could be some sort of backup procedure (perhaps prompted by the
instability of the BGP link).

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

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