Longest prepend( 255 times) as path found

William Herrin bill at herrin.us
Sat Aug 27 05:24:03 UTC 2022

On Thu, Aug 25, 2022 at 10:58 AM Tom Beecher <beecher at beecher.cc> wrote:
> If I was running an edge device with a limited FIB, perhaps
>I might drop it to save memory. If I had beefier devices, perhaps
>I would just depref it.

Hi Tom,

Neither of these answers make much sense to me. If you're using a
default route to overcome a limited FIB, you want a more reliably
chosen set of routes to filter than the stray error route that
shouldn't have reached you.

Nearly all paths on the Internet are still under 64 hops wide (packet
TTL of 64) so finding a non-customer route with more than double that
number of elements in the AS path suggests someone tried to do
something fancy in a local environment and it leaked. Not only is it
reasonably safe to discard such routes, long AS paths have been
responsible for triggering bugs in multiple BGP implementations.
Failing to filter it may actually be harmful to folks downstream from

Bill Herrin

For hire. https://bill.herrin.us/resume/

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