The /24 is as small as it will get before it cuts into profits for the tiny bit of administration it would take to announce /25, /26.
This argument is almost as old as my kids.
Is it fair or just, probably not, but that's they way the consensus seems to want it.
Richard
Richard Golodner
Infratection IT Services
-------- Original message --------
From: William Herrin <bill@herrin.us>
Date: 10/11/22 16:00 (GMT-06:00)
To: Matthew Petach <mpetach@netflight.com>
Cc: nanog@nanog.org
Subject: Re: any dangers of filtering every /24 on full internet table to
preserve FIB space ?
> Wouldn't that same argument mean that every ISP that isn't honoring
> my /26 announcement, but is instead following the covering /24, or /20,
> or whatever sized prefix is equally in the wrong?
>
> What makes /24 boundaries magically "OK" to filter on,
Hi Matthew,
/24 is the consensus filtering level for Internet-wide routes and it
has been for decades. It became the consensus as a holdover from
"class C" and remains the consensus because too many people would have
to cooperate to change it. Indeed, a little over a decade ago some
folks tried to change it to /19 and then /20 for prefixes outside "the
swamp" and, well, they failed. Likewise, more than a few folks
announce /26's to their immediate transit providers and they simply
don't move very deep into the system -- nobody has any expectation
that they will.
> To wrap up--I disagree with your assertion because it depends entirely
> on a 'magic' /24 boundary that makes it OK to filter more specifics smaller
> than it, but not OK to filter larger than that and depend instead on covering
> prefixes, without actually being based on anything concrete in BGP or
> published standards.
Got any better reasons besides disliking the consensus?
Regards,
Bill Herrin
--
For hire. https://bill.herrin.us/resume/