any dangers of filtering every /24 on full internet table to preserve FIB space ?

William Herrin bill at
Tue Oct 11 14:40:54 UTC 2022

On Mon, Oct 10, 2022 at 3:37 PM Matthew Petach <mpetach at> wrote:
> They became even more huffy, insisting that we were breaking the internet by not
> following the correct routing for the more-specific /24s which were no longer present
> in our tables.  No amount of trying to explain to them that they should not advertise
> an aggregate route if no connectivity to the more specific constituents existed seemed
> to get the point across.  In their eyes, advertising the /24s meant that everyone should
> follow the more specific route to the final destination directly.

Hi Matthew,

They were correct. If the /24 was reaching your network, traffic
should not have been following the /20. In your version, they would
have to disaggregate the /20 into 16 /24s just because you didn't want
to honor most-specific path routing. That's not what anybody wants.
Least of all you.

One of my service providers has multiple disconnected sites. At each
site they advertise the Internet's full BGP table to me -except for-
the routes to their other sites. They insist they're doing the right
thing but they're not. The BGP table they send me is not full, and
when I need to talk to many of -their- servers my traffic ends up
routing through one of my other service providers.

I'm not paying them enough to make a big stink about it but if I was
you can bet I'd take them to task.

Bill Herrin

For hire.

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