On Tue, Oct 11, 2022 at 1:15 PM Matthew Petach <mpetach@netflight.com> wrote:
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/