RE: IPv4 flag day

[Gary Sparkes via NANOG <nanog () lists nanog org>]

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. 

-----Original Message-----
From: Aaron C. de Bruyn via NANOG <nanog () lists nanog org> 
Sent: Friday, June 19, 2026 3:55 PM
To: North American Network Operators Group <nanog () lists nanog org>
Cc: Marco Moock <mm () dorfdsl de>; Aaron C. de Bruyn <aaron () heyaaron com>
Subject: Re: IPv4 flag day

On Fri, Jun 19, 2026 at 12:47 PM Marco Moock via NANOG < nanog () lists nanog org> wrote:

> Am 19.06.26 um 21:21 schrieb Aaron C. de Bruyn:
> > I don't want to renumber everything because I ditch one ISP and 
> > switch to another.
>
> Get your own prefix from RIR and let your ISP route it to your. If you 
> switch the ISP, let the new ISP route it to you. It is even possible 
> to have 2 ISPs that route the same prefix to you - without having you own ASN.

A SMB doesn't have to do that in IPv4 using RFC1918 and NAT.
Pretty sure there's a cost to get a /48 from an RIR and probably costs with the various ISPs to route to you.

While I'll admit I'm not an IPv6 expert by any means, it doesn't seem like there's a clean path from:
"I have a stable internal network addressing scheme under IPv4 that's independent of whatever random ISP I'm using  and 
it sucks I have to use NAT, but it's easy" to "There are enough addresses for everyone to have their own internet, so 
I'll come up with my own /48 (or get one for free like I had in IPv4) and simply 'connect' to my ISP and it works...no 
NAT and no port forwarding required...just nice simple firewall rules".

-A
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