Re: maximum ipv4 bgp prefix length of /24 ?

[Matthew Petach <mpetach () netflight com>]

On Wed, Oct 4, 2023 at 11:33 PM Mark Tinka <mark@tinka.africa> wrote:

> On 10/5/23 08:24, Geoff Huston wrote:
>
> The IPv6 FIB is under the same pressure from more specifics. Its taken 20
> years to get there, but the IPv6 FIB is now looking stable at 60% opf the
> total FIB size [2]. For me, thats a very surprising outcome in an
> essentially unmanaged system.
>
>
> Were you expecting it to be lower than IPv4?
>
> Mark.

I've dug through the mailman mirror on nanog.org, and there's currently no
post by Geoff Huston saying that:

https://community.nanog.org/search?q=geoff%20huston%20order%3Alatest

But I'll play along.

There's significantly less pressure to deaggregate IPv6 space right now,
because we don't see many attacks on IPv6 number resources.
Once we start to see v6 prefix hijackings, /48s being announced over /32
prefixes to pull traffic, then I think we'll see IPv6 deaggregation
completely swamp IPv4 deaggregation.
Either that, or content sites will simply turn off IPv6 AAAA records during
periods of attack, and let the traffic shift back to IPv4 instead.

When your IPv4 space gets hijacked, there's no fallback; you announce /24s,
because that's all you *can* do.
When your IPv6 space gets hijacked, there's always IPv4 as the fallback, so
there's less pressure to announce /48s for all your space, just in case
someone tries to hijack itl.
Otherwise, we would already be seeing the IPv6 deaggregation completely
overwhelming the IPv4 deaggregation.

Thanks!

Matt