BGP attributes through IGP

Elliot Finley efinley.lists at gmail.com
Thu Mar 6 22:10:42 UTC 2014


iBGP over GRE?



On Thu, Mar 6, 2014 at 2:58 PM, Bryan Ashley <bja8180 at gmail.com> wrote:

> 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 ytti.fi> 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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