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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