Subject: Re: HEADS UP! Default value of ip6_v6only changed
To: NetBSD OS PMC <>
From: Perry E. Metzger <>
List: tech-net
Date: 10/28/2003 09:25:08
NetBSD OS PMC <> writes:
> The default value of ip6_v6only (sysctl net.inet6.ip6.v6only) has
> been changed.  The new value brings us closer in line with current
> RFC-defined behavior and practices.
> Itojun still has significant concerns about the new default behavior.
> His concerns have been well-documented in

He's not the only one. The rule of least surprise is violated by this
(we have two protocols stacks that are now mysteriously linked), and
this causes substantial pain to many of us. There is also very
widespread opposition to such behavior in the IPv6 community.

Might I suggest that Core convene a group of v6 experts to re-consider
the question? It might also be reasonable to request a more current
opinion from the appropriate IETF working group -- I suspect that they
would no longer support mapping by default.

By the way, as a matter of process, it might be useful if core announced
that it was considering changes like this and explicitly solicited
input. If I had known that you were considering this, I would have
spoken up. I had assumed the recent discussion on the subject was just
the usual argumentation -- I didn't know you were going to make a decision.

Perry E. Metzger