Subject: Re: [v6ops] Implementation Status of PREF64

From: Lorenzo Colitti <[email-masked]>
Date: Tue, 28 Sep 2021 14:21:20 +0900

On Tue, Sep 28, 2021 at 1:54 PM Owen DeLong <owen=
[email-masked]> wrote:

> No… That’s not what it amounts to.
>
> It amounts to a machine can only use the network _IF_ it completes 802.1x
> Authentication _AND_ the IP address(es) it is using match the DHCP server’s
> expectation of the address it issued to the MAC address in question.
>

Why would you want to do this? IPv6 addresses are plentiful and ephemeral.
What does it matter to some server on the Internet (or, in general,
off-link) if a given host uses 2001:db8:1:2:3::f00 or 2001:db8:1:2:3::b00
or both? Why take the privacy implications of using a fixed IID (because
DHCPv6 can't seamlessly change IIDs) to talk to all off-link destinations
all the time?

> This is better than the DHCP version above because it allows the client to
> use multiple IP addresses and does not need to be re-done when the IP
> address changes.
>
> Sometimes the network administrator doesn’t want the host using multiple
> IP addresses for a variety of reasons.
>

Ok, but that's also harmful for a variety of reasons, and for general
purpose devices, it's not recommended by the IETF. That's exactly what RFC
7934 is about - explaining why it's harmful.

I repeat… Your anti-DHCP religion is NOT HELPING.

Not helping with what? The transition to IPv6? But if so - why bother using
IPv6 if it's just just 128-bit IPv4, with one address per host, no dynamic
address changes (because DHCPv6 can't really support that) and NAT (because
if you can't tell the host that its network configuration has changed, you
need to ensure that the configuration *doesn't* change)? Why use IPv6 to do
that, which requires hosts to implement all the associated complexities
such as NAT traversal, NAT keepalives, etc.? That model works perfectly
well today using IPv4, and I'm pretty sure that OS support for IPv4 isn't
going anywhere any time soon.