BGP attributes through IGP

Bryan Ashley bja8180 at
Thu Mar 6 21:58:51 UTC 2014

so this scenario was a much more scaled down version of the actual
topology.  Basically I have a "gap" of routers that I don't manage or have
access to in between mine running eBGP.  We are collecting some metrics and
doing monitoring on the AS-PATH of the routes received, among other
attributes, for both ends so losing some of this information is a problem.
 Again, I know the right answer here is to run iBGP across the IGP and I am
fighting that fight but it got me looking for alternative solutions and
figured I would see if anyone else ever had to come up with a creative
solution before.

On Thu, Mar 6, 2014 at 4:09 PM, Saku Ytti <saku at> wrote:

> On (2014-03-06 10:37 -0500), Bryan Ashley wrote:
> > My searches have come up a little short however I found a couple
> references
> > to using automatic-tag and as-path tag to carry this through.  I cant
> seem
> > to find any Junos reference information on this so wanted to reach out to
> > the ether and see if others have faced this situation before or have any
> > other recommendations on solutions.
> I don't think JunOS supports this.
> It's bit of hack at any rate. It's not transporting AS_PATH, it's
> transporting
> single 16b ASN.
> It's essentially abusing (some what well-defined and interoperable abuse)
> 32b
> tag field for this purpose.
> Maybe you could try to do some of this manually, set some tags, which
> trigger
> 'set then origin x', as-path-expand/prepend might be more challenging.
> Recommendation for solution might be easier with rationale why you need to
> transport origin+aspath over IGP.
> --
>   ++ytti

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