Subject: [BEHAVE] NAT66 and dynamic Ipv6 allocations

From: Roque Gagliano <[email-masked]>
Date: Wed, 26 Nov 2008 16:55:04 -0200

Hi,

I was thinking about this 66 NAT and I have an example where it may  
actually be useful to me today.

At home I have a 6to4 configuration using DD-WRT and some special  
scripts. The problem is that my service provider changes my IPv4  
address every 12 hours, or every time that I re-connect. I worked at  
that specific provider, so I know that they have some "business"  
driven reasons to do so. The problem is that now, my 6to4 prefix  
changes over time. To solve this problem I configured a short radvd  
AdvValidLifetime. So, still my PCs IPv6 addresses changes every 12  
hours. So I was thinking that it could be a good idea to have a NAT66  
in order to maintain local addresses in the inside side.

So, what his made me think is about the necessity of a NAT66 when  
having (for any reasons) dynamic IPv6 allocations by ISPs. It could  
make sense to maintain long living IPv6 addresses in the inside side,  
while the ISP is playing with your public side.

Regards,

Roque
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From: Brian E Carpenter <[email-masked]>
Date: Thu, 27 Nov 2008 10:30:03 +1300

Roque,

> So, what his made me think is about the necessity of a NAT66 when having
> (for any reasons) dynamic IPv6 allocations by ISPs. It could make sense
> to maintain long living IPv6 addresses in the inside side, while the ISP
> is playing with your public side.

What's wrong with the standard IPv6 solution to this, i.e., use a ULA
prefix for internal traffic, and only use a global prefix, in your
case 6to4, for external traffic?

   Brian

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From: Peter Dambier <[email-masked]>
Date: Thu, 27 Nov 2008 01:04:47 +0100

Thank you Brian,

for ULA.

That is just the missing math to proof NAT66 wont work.

Here in germany you dont get IPv6 connectivity today.

The house visavis and my house cannot ISATAP because
we are both imprisoned behind NAT44 but they have ULA1
and I have ULA2 and via a wireless bridge we can
communicate IPv6, high speed no router needed.

Now, in order to hit the fan, our ISP has sent us
two little packages containing even smaller boxes
to replace our NAT44 with NAT66.

I never got my box working nor did the people from
the house over the street until those people from
the computer shop at the end of the street adviced
us to keep both boxes unplugged.

The story gives a perfectly new meaning to uPnP.
Unplug and it plays :)

But how can I configure the firewall with my
box unplugged? After all I dont know what password
that computer shop is using.

Nevertheless I still have a problem.
How can I follow this constantly changing 6to4 address?

   Peter

> case 6to4, for external traffic?

- --
Peter and Karin Dambier
Cesidian Root - Radice Cesidiana
Rimbacher Strasse 16
D-69509 Moerlenbach-Bonsweiher
+49(6209)795-816 (Telekom)
+49(6252)750-308 (VoIP: sipgate.de)
mail: [email-masked]
http://iason.site.voila.fr/
https://sourceforge.net/projects/iason/
http://www.cesidianroot.net/
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From: Keith Moore <[email-masked]>
Date: Thu, 27 Nov 2008 01:51:22 -0500

> case 6to4, for external traffic?

I've never figured out how applications are supposed to know, absent
explicit configuration for every application, whether traffic is
"internal" or "external".  In particular for any multiparty application
that does referrals, it doesn't suffice to simply choose the source
address based on the destination address.  What matters is whether all
of the application's peers are "internal" or "external" and the
application may not know that a priori.

Keith

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From: Iljitsch van Beijnum <[email-masked]>
Date: Thu, 27 Nov 2008 13:40:09 +0100

On 26 nov 2008, at 19:55, Roque Gagliano wrote:

> my PCs IPv6 addresses changes every 12 hours. So I was thinking that  
> it could be a good idea to have a NAT66 in order to maintain local  
> addresses in the inside side.

With IPv6, the routers can push out a new prefix using router  
advertisements so the new addresses are used for new sessions  
immediately, although the old sessions will of course use the old  
addresses and break, but that will happen with NAT, too. So NAT  
doesn't really buy you anything here in a home setup where everything  
is autoconfigured.

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From: Brian E Carpenter <[email-masked]>
Date: Fri, 28 Nov 2008 13:58:45 +1300

> application may not know that a priori.

Sure, because we only did half a job on defining what "scope" means.
As far as I can see, in the end there is no alternative to trial
and error in the most complex cases.

    Brian