I am not checking my emails until Nov 14th, 2025. Thanks, Samaneh

On Nov 10, 2025, at 12:35 PM, Vasilenko Eduard via NANOG 
<[email protected]> wrote:

Hi Douglas,
You probably have the portal (that probably connected to the billing system).
Why not to put the  statement "This IPv4 block is delegated to you, and you use 
it as you see fit... And the default IPv4 route is the same IP as the default 
IPv6 route"
On their "personal account" (or whatever you call their personal page)?
It should resolve the address delivery problem.

Of course, many of them would still ask questions, but they would ask questions 
anyway... you could not teach the whole market.
Ed/
-----Original Message-----
From: Douglas Fischer via NANOG <[email protected]>
Sent: Monday, November 10, 2025 13:52
To: [email protected]
Cc: Douglas Fischer <[email protected]>
Subject: DHCP v6 for IPv4 Delegated prefrefix - Wan IPv6 Only to be routed
with RFC8950

Trying to stay focused on IPv4 as a Service...

I dream of being able to build a backbone that is truly IPv6 Only! But even
taking some steps in 464xlat environments, there are still commercial
demands that still impose the use of Dual-Stack. This is the case with clients
who require (and pay for) a routed IPv4 address.
I've been looking for a solution for some time to deliver a routed IPv4 address
to the client, and to do so in a way that doesn't depend on exchanging
information via email and similar means to let the client know which IPv4
block to use.

Note 1: Almost all are business subscribers, and 95% of the time they purchase
the delivery of an IPv4 /32 address as a service.

In cases where we had access to the device, we frequently used DHCP IPv4
Option 121, pointing the routed block (/32, /31, or even /29) with the next-
hop of the route pointing to the same IP address on the subscriber's side of
the /30 link network with private IPs.
The complex part is that the subscriber's "IT Guy" needs to have a minimum
understanding of networking and know that they have to use those IPs as
needed.
In most cases, this is done in a loopback network, to be used as a VPN
endpoint, for NAT... And in very rare cases, routed to the client's internal
network to be used as a loopback for servers and similar things.
We even developed some JerryRig scripts to retrieve this route information
taught via DHCP IPv4 Option 121 and "semi-automate" the use of these IPs in
loopbacks in address lists to facilitate client use. But this is only possible 
on
CPEs where scripting is allowed, and even then it's a big challenge to handle
multiple NOS on CPEs.

My current goal is to find a way to deliver an IPv4 prefix to the subscriber and
tell it, "This IPv4 block is delegated to you, and you use it as you see fit... 
And
the default IPv4 route is the same IP as the default IPv6 route."

Note2: I tried doing this with the 6PE format 0:0:0:0:0:ffff:IPv4_Block.
But I haven't had success with common CPEs.

I feel there's a good chance I'm reinventing the wheel. And this is already
handled in some DHCPv6 options.
And that's precisely why I'm asking my colleagues here if there's already
something that can help me.
If there isn't... Trying to keep the focus on IPv4 as a Service... Would it be 
too
much to dream of setting something like that up?

Note 3: I even considered JerryRiging the JerryRig. That would be a way to
"teach via DHCPv6" that these clients have to establish a BGP session over
IPv6 with IPv4 and IPv6 Address-Families. But I didn't see that this would help
much in putting IPv4 in the loopback of the CPEs. So I left that aside.

Any colleagues with suggestions on how to solve this type of problem?

P.S.: Unfortunately, my customer base is still far from being able to do without
IPv4. And handling things within the client's network IS NOT AN OPTION! Just
like "464XLAT 1:1" isn't an option either due to the specific demands of the
clients.

--
Douglas Fernando Fischer
Engº de Controle e Automação
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