RE: IPv4 flag day

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

Well, you have the same problem with v4 or v6.

In this scenario we’re talking about, you have two separate IPv4 ranges (one per provider) anyway. So the mechanisms 
are all still entirely the same.

But as I was noting, there’s ULA addressing, so you’re not renumbering at all when you move ISPs internally, NPT 
handles that on the front end for you.

In enterprise, well, you don’t have this concern, you’ll be using BGP on your links. Or tunneling to 
datacenters/central appliances, or what have you.


From: Aaron C. de Bruyn <aaron () heyaaron com>
Sent: Friday, June 19, 2026 3:22 PM
To: North American Network Operators Group <nanog () lists nanog org>
Cc: sronan () ronan-online com; Marco Moock <mm () dorfdsl de>; Gary Sparkes <gary () kisaracorporation com>
Subject: Re: IPv4 flag day


On Fri, Jun 19, 2026 at 12:06 PM Gary Sparkes via NANOG <nanog () lists nanog org<mailto:nanog () lists nanog org>> 
wrote:
Internal clients are 1:1 NPT'd to provider addresses, and on failover, the internal addressing doesn't change, but all 
the traffic flips to the other provider's addresses.

And now we've got to have a mechanism to update external DNS for the SMB or Enterprise that hosts their own MX, a 
remote access server, and all those SSH port forwards the IT guys use to remotely access/manage stuff.

I thought I was promised an IPv6 where there were so many dang addresses that every business could have their own 
*public* /48 with enough room left over to allocate a /48 to every molecule on the planet or whatever.

I don't want to renumber everything because I ditch one ISP and switch to another.
In IPv4 I don't have to thanks to RFC1918 space.
In IPv6 I guess I have fc00::/7 that gets allocated "pseudo-randomly".

So in IPv6 I either have to renumber because I ditched some ISP for another...or I have to pay for my addressing space 
and my ISPs have to support routing my address space, right?

-A


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