Re: IPv4 flag day

[Marco Moock via NANOG <nanog () lists nanog org>]

Am 19.06.26 um 22:23 schrieb Aaron C. de Bruyn:
> On Fri, Jun 19, 2026 at 1:03 PM Gary Sparkes <gary () kisaracorporation com>
> wrote:
>
> > The clean path would be NPTv6 with ULA for the same exact setup.
> >
> > It would slot in and work identically to how the IPv4 deployment is today.
> >
> > Instead of RFC1918, you have ULA addressing. Same concept.
> >
> > Except with NPTv6 you're doing 1:1 and eliminate PAT.
> >
> > Of course, if you're single provider, might as well just use prefix
> > delegation, NPT's real shine is the multi-WAN scenario with no upstream
> > routing protocol that sparked off a lot of discussion.
> >
> > As to changing providers when using prefix delegation, most stuff can
> > auto-update itself, but otherwise it's a simple find/replace exercise in
> > documentation and records when your provider prefix changes as the last
> > half of the address is entirely stable, and the first half is (mostly)
> > provider.
>
> Maybe I need to do a bit more digging as I'm not an expert at IPv6--but
> aren't ULA addresses basically randomly assigned to hosts based on their
> NIC HW address and a few other things?

You should really, really improve your IPv6 knowledge.

> A short example from a very large client I manage:
> They use IPv4 10/8
> The next octet is allocated for the state the office is located in "plus
> 100".  So if they open an office in Alabama (22nd state to join the union),
> it's gonna be 10.122/16.
> The third octet is assigned sequentially.  The first office opened in
> Alabama is 10.122.0.0/24.
> The last octet is static.  Router at .254, linux server at .250, Windows
> (ugh) RDP server at .249, workstations are DHCP between .100 and .199,
> etc...

That is almost impossible for large networks - as the address space if 
often too low. BTDT.

> You can give me nearly any IP from this client and I know the device.
> But ULA gives me: fe80::ae1f:6bff:feb0:3c98/64

You seem to have no clue that ULA and link-local are different.
fd00::/8 is ULA. You can use fd00:random::/48 and then set every bit in 
the last 80 bit.

> Hard-code the address to fe80::122:00000:250/64 (just to know it's a linux
> server in Alabama) and then set up NPTv6...and update a *ton* of DNS info
> so the rest of the world can easily get to the correct machines?

No, you only use fe80 for link-local communication (mostly NDP, some 
discovery protocols), nothing else.


--
Gruß
Marco

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