Re: [Int-area] practical issues with using v4-mapped addresses for nat64

[Julien Laganier <julien.IETF at laposte.net>]

On Wednesday 23 July 2008, Dave Thaler wrote:
> I think your point is that in an IPv6-only network, native IPv4
> obviously won't work, and having v4mapped addresses on the wire won't
> work from the current dual-stack OSs tested.  So you either need them
> fixed or you need them to use some prefix other than the v4mapped
> range.
>
> Hence Brian Carpenter's suggestion to default to v4mapped but allow
> configuration to support some other prefix, which sounds reasonable.
> There's no magic answer that's occurring to me.

FWIW:

faithd, an IPv6-to-IPv4 TCP relay for *BSD, and totd, a DNS proxy and 
translator for IPv6 and IPv4, works by embedding IPv4 addresses into 
IPv6 ones thanks to use of a designated, locally assigned IPv6 prefix:

<http://www.daemon-systems.org/man/faithd.8.html>
<http://www.aioe.org/cgi-bin/man2web?program=totd&section=8>

I'd used that setup in 2003 on an IPv4-free FreeBSD laptop (i.e. no IPv4 
address configured) for daily use (e.g. mail, www, etc.) and it worked 
well.

In case somone has no globally routable IPv6 prefix assigned, it is 
possible to use a ULA prefix. It could also has the "advantage" to 
limit the risk of packets containing these IPv4 addresses embedded in 
IPv6 addresses as destination leaking in the outside Internet.

--julien
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