Subject: Re: How to use properly ipv6 autoconf over a router interface?
To: None <tech-net@NetBSD.org>
From: David Young <email@example.com>
Date: 05/05/2006 11:52:09
On Thu, May 04, 2006 at 09:52:29PM +0000, Martijn van Buul wrote:
> It occurred to me that David Young wrote in gmane.os.netbsd.devel.network:
> > On Thu, May 04, 2006 at 10:59:07AM +0000, Martijn van Buul wrote:
> >> It occurred to me that David Young wrote in gmane.os.netbsd.devel.network:
> >> > I can easily imagine a scenario where my Powerbook auto-configures as
> >> > a host on a WiFi LAN, but it is a router for my cell and for my PDA on
> >> > a Bluetooth PAN.
> >> I'm smelling IPv6 NAT here.
> > If people only know/think enough about the topic to speak about "smells"
> > and "messiness",
> Maybe I *do* know more of the subject, and I'm merely a few steps ahead of
> But well then, Mr. Guru, please tell me how to address the following
> Really, the only way to make *any* kind of automagic routing possible would
> be address rewriting. IPv6 already autoconfigures link local addresses
> for you, but they'd have to be rewritten to something global. In other words,
> IPv6 NAT. And you may call me names and ridicule me, but really:
You're the one calling names. It was not my intention to ridicule you,
sorry if it came off that way.
Clearly you have thought a lot about the question. So why didn't you
begin with your detailed and informative response (which I trimmed above)
instead of "I'm smelling IPv6 NAT here," which sounds so flippant?
Everyone has leapt to the conclusion that any IPv6 router that
autoconfigures for subnet X on one interface must necessarily advertise
subnet X on its second interface. Suppose the IPv6 router is your
notebook computer. The subnet on the second interface is part of a
/48 at home; your connection to home is a private tunnel. The first
interface auto-configures for an arbitrary IPv6 subnet at work, or at
the coffeeshop, or wherever you are that day. Your notebook forwards
packets from the second interface to the tunnel interface. I believe
this setup is forbidden both by the current standards and by the KAME
IPv6 stack, but maybe I am mistaken. (It looks like IETF's NEMO working
group contemplates just this kind of "mobile router" scenario.) I am
interested to hear your opinion on the matter.
David Young OJC Technologies
firstname.lastname@example.org Urbana, IL * (217) 278-3933