I could be wrong but i think i remember internet bgp backbones not
advertising any thing smaller than a /19 or /20.
_
Jason Price
On Thu, 25 Jan 2001, John Neiberger wrote:
> An addendum:
>
> I checked several Sprint locations and they are all using the Sprint path.
> The only Sprint location that is using the verio path is the "Sprint NAP"
> location on the Broadwing LG site. In fact, from Broadwing's site, every
> place says that it's using the Verio path, which is interesting.
>
> Just about every place else I check now, though, shows that the Sprint path
> is being chosen which is how I intended it. I'd rather not have had to
> prepend our AS to the Verio side because I'd like our customers who use
> Verio to take the Verio path. As it stands, it appears that they are taking
> the Sprint path, as well.
>
> Oh well, a-tweaking I will go!
>
> John
>
> > We have connections to Sprint and Verio and I had BGP up and running with
> > Sprint for a couple of weeks. It appeared to me that they were
> advertising
> > our specific /24, 205.243.23.0, along with the rest of their
> advertisements.
> > Today, I turned up a BGP session with Verio, again just advertising our
> /24.
> >
> > Soon afterward, with the help of lookingglass sites I noticed that
> > everywhere I checked was using the Verio path, including Sprint! I know
> > that a common cause of this would be if Sprint were not advertising our
> > more-specific /24, but Verio was. This would create a more specific
> match
> > through Verio. However, I don't think this is the case.
> >
> > Next, I prepended our AS, 19105, twice on the Verio side and then checked
> > the LG sites again. Now, all were using the Sprint path. Next, I tried
> > reducing the number of prepends to one and again most places--including
> > Sprint--were using the Verio path.
> >
> > What would cause this behavior? Even with no prepends, it looks like the
> AS
> > path for a lot of these locations (NAPs) was the same length. If so, and
> > both ISPs are advertising our /24 like they're supposed to be, why would
> I
> > have to prepend our AS twice to force routers to choose the Sprint path?
> >
> > I think I just may have thought of a reason. If there were locations
> that
> > were aggregating Sprint's routes before advertising them to peers, that
> > would cause this behavior. But if that were the case, why would
> prepending
> > an AS matter at all? The Verio path would always be preferred because it
> is
> > most specific, right?
> >
> > Arg.... I *thought* I understood this!
> >
> > Any ideas?
> >
> > Thanks,
> > John
> >
> >
> >
> >
> >
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>
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