Smaller than a /24 for BGP?

Wed Jan 25 04:12:47 UTC 2023

I have two thoughts in relation to this:

1) It's amazing how many threads end up ending in the (correct) summary
that making an even minor global change to the way the internet works
and/or is configured to enable some potentially useful feature isn't likely
to happen.

2) I'd really like to be able to tag a BGP announcement with "only use this
announcement as an absolute last resort" so I don't have to break my
prefixes in half in those cases where I have a backup path that needs to
only be used as a last resort.  (Today each prefix I have to do this with
results in 3 prefixes in the table where one would do).

And yes. I know #2 is precluded from actually ever happening because of
#1.   The irony is not lost on me.

On Tue, Jan 24, 2023, 7:54 PM John Levine <johnl at iecc.com> wrote:

> It appears that Chris J. Ruschmann <chris at scsalaska.net> said:
> >-=-=-=-=-=-
> >How do you plan on getting rid of all the filters that don’t accept
> anything less than a /24?
> >
> >In all seriousness If I have these, I’d imagine everyone else does too.
>
> Right. Since the Internet has no settlements, there is no way to
> persuade a network of whom you are not a customer to accept your
> announcements if they don't want to, and even for the largest
> networks, that is 99% of the other networks in the world. So no,
> they're not going to accept your /25 no matter how deeply you believe
> that they should.
>
> I'm kind of surprised that we haven't seen pushback against sloppily
> disaggregated announcements.  It is my impression that the route table
> would be appreciably smaller if a few networks combined adjacent a
> bunch of /24's into larger blocks.
>
> R's,
> John
>
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