One router - Two ASN

Henrique de Moraes Holschuh hmh at
Sat Mar 24 14:23:37 CET 2012

On Sat, 24 Mar 2012, Oleg wrote:
> On Sat, Mar 24, 2012 at 09:00:34AM +0100, Mi??osz Oller wrote:
> > How can I run two asn on one router?
> > 
> > Example:
> > 
> >   ISP1 
> >      |
> > ---------------
> > | AS1 - AS2 |
> > ---------------
> >                |
> >             ISP2
> > 
> > ISP1 is connected to AS1, ISP2 is connected to AS2. How can I configure
> > connection AS1-AS2 with bgp protocol on localhost (neighbor ip and
> > source address)? 
>   What about local option of bgp protocol?

The documentation (or the wiki, I don't recall) mentions that you *may*
have to handle some AS_PATH details manually.  That means it can be
done, but the documentation is annoyingly vague about what you have to
do to get it to work well (and safely).

Anyway, you already have to handle mostly everything manually anyway as
far as enforcing route/attribute sanity on BGP import and export. bird
automates very little as far as eBGP sanity checking goes: it validades
the BGP wire protocol, handles AS4_PATH transparently (annoyingly still
documented as "not supported" in one of the bgp protocol headers), and
probably a few other details, but that's it.  Look at the BGP filtering
example in the Wiki, that thing should be part of the official
documentation, as it ends up documenting stuff that you _must_ always do
in iBGP/eBGP filters...

  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh

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