[AusNOG] Nearly IPv6 Only Dual Stack Hosts

[Mark Smith]

Hi,

TL;DR: If you want to see how much of the Internet is available over
IPv6, without IPv4, run up a Kea DHCPv4 server with the following
configuration:

 https://ipv6tao.blogspot.com/2025/12/nearly-ipv6-only-dual-stack-hosts.html

There's work going on in the IETF regarding how to both allow IPv4 and
IPv6 to coexist in a network while also phasing IPv4 out for hosts
that don't need it when all of their applications speak IPv6.

I've written up an Internet Draft that takes advantage of a technique
I mentioned on this lighting talk from 2018 - using a subnet mask of
255.255.255.255 - to effectively disable IPv4 via DHCPv4.

"A dirty trick to save a couple of IPv4 addresses on a LAN link"
https://www.ausnog.net/sites/default/files/ausnog-2018/presentations/2.10.2_Mark_Smith_AusNOG2018_Lightning.pdf

The Internet Draft:

"Nearly IPv6 Only Dual Stack Hosts"
https://datatracker.ietf.org/doc/draft-smith-v6ops-nearly-ipv6-only-dualstack-hosts/

I've tested it with various dual stack clients I have e.g. Fedora 43,
Windows 11, Google TV with Chromecast, and it seems to work fine with
them.

I'm curious to find out how things like Mac OS, Iphones and any other
dual IPv4/IPv6 stack hosts work with this Kea DHCPv4 server
configuration:

https://ipv6tao.blogspot.com/2025/12/nearly-ipv6-only-dual-stack-hosts.html

If you provide me with some testing and feedback, I'll put you in the
acknowledgements section of the Internet Draft. There's no guarantee
it will be published as an RFC, however if it is, your name will
permanently be in an IETF RFC.

Thanks very much,
Mark.