nanog mailing list archives

Re: BGP prefix filter list


From: Tom Beecher <beecher () beecher cc>
Date: Wed, 15 May 2019 15:20:42 -0400

At a previous company , about 10-ish years ago, had the same problem due to
equipment limitations, and wasn't able to get dollars to upgrade anything.

The most effective thing for me at the time was to start dumping any prefix
with an as-path length longer than 10. For our business then, if you were
that 'far away' , there wasn't any good reason for us to keep your route.
Following default was going to be good enough.

It's still a reasonable solution I think in a lot of cases to filter out a
lot of the unnecessary prepend messes out there today.

On Wed, May 15, 2019 at 7:45 AM Baldur Norddahl <baldur.norddahl () gmail com>
wrote:

Hello

This morning we apparently had a problem with our routers not handling
the full table. So I am looking into culling the least useful prefixes
from our tables. I can hardly be the first one to take on that kind of
project, and I am wondering if there is a ready made prefix list or
similar?

Or maybe we have a list of worst offenders? I am looking for ASN that
announces a lot of unnecessary /24 prefixes and which happens to be far
away from us? I would filter those to something like /20 and then just
have a default route to catch all.

Thanks,

Baldur



Current thread: