Re: DHCP v6 for IPv4 Delegated prefrefix - Wan IPv6 Only to be routed with RFC8950

[Maria Matejka via NANOG <nanog () lists nanog org>]

Hey, Douglas,

On Mon, Nov 10, 2025 at 07:52:06AM -0300, Douglas Fischer via NANOG wrote:

> [...]
>
> 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.

You mean sending delegated prefixes from the DHCPv6 server? I'm very
much afraid that the client-side implementations do not expect that,
but on the other hand, this is something definitely worth trying and
persuading the clients to implement.

> I feel there's a good chance I'm reinventing the wheel. And this is already
> handled in some DHCPv6 options.

I have not found any but I'm not a DHCP expert.

So with that, my guess would be to look into at least OpenWRT but also
poke CPE device manufacturers about this, because I'm afraid that this
is ultimately going to need an implementation anyway, maybe even a draft
explicitly specifying that sending an IPv4 prefix inside OPTION_IAPREFIX
is actually a thing.

Have a nice day!  
Maria

-- 
Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
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