Re: IPv4 flag day

[Arie Vayner via NANOG <nanog () lists nanog org>]

Hi everyone,

There is also a significant set of use cases that currently work better, or
at least more easily, with NAT.

The most common example is small branch sites with dual ISP uplinks. There
are a vast number of these sites deployed using two small provider-assigned
(PA) NAT pools. This setup is widely understood, simple to implement, and
reliable.

Moving these sites to IPv6 via BGP is often not feasible. Many ISP circuits
do not support BGP, and the teams operating these sites lack the time to
navigate that complexity. Furthermore, other IPv6 dual-homing options often
don't align with enterprise requirements or expected complexity (or really
simplicity) levels.

In my view, this is a core reason why IPv6 adoption remains low in the
enterprise space: it requires fundamental paradigm shifts rather than a
simple protocol update.

Thanks,
Arie


On Tue, Jun 16, 2026, 8:10 AM Tom Beecher via NANOG <nanog () lists nanog org>
wrote:

> > Is NAT still such a severe problem that we needed a different protocol?
> > Ask 1000 NANOG engineers, get 1000 different answers. In practice, no.
> > IPv4 still works.
>
>
>  There are also plenty of well established things that NAT causes problems
> for, along with less than desirable protocol and standardization choices
> that have been made because of the existence of NAT.
>
> We've gotten really good at engineering ways to disguise these issues so
> users don't notice them. On one had that's good because user/application
> experiences are better, on the other hand it sucks because people think a
> non-visible problem isn't a problem anymore.
>
> On Tue, Jun 16, 2026 at 10:53 AM Brian Knight via NANOG <
> nanog () lists nanog org> wrote:
>
> > On 2026-06-16 01:33, Saku Ytti via NANOG wrote:
> > > Does anyone feel responsibility for the dual stack mess we've created?
> > > It wasn't here when we found the Internet, and we're going to leave it
> > > here after we leave, does not really jive with the whole leave
> > > campground cleaner than found it ethos.
> >
> > It was the most comprehensive solution for the NAT problem. But NAT
> > became the accepted way we connect to the Internet.
> >
> > World + dog knows how to connect to it, troubleshoot it, look at NAT
> > tables on their edge firewall or router.
> >
> > Is NAT still such a severe problem that we needed a different protocol?
> > Ask 1000 NANOG engineers, get 1000 different answers. In practice, no.
> > IPv4 still works.
> >
> > Economics are a slightly different story, but so far, IPv4 space isn't
> > prohibitively expensive.
> >
> > -Brian
> > _______________________________________________
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> >
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