IPv6 routing /48s

Jack Bates jbates at brightok.net
Wed Nov 19 22:05:20 UTC 2008

Nathan Ward wrote:
> The problem here is XPSP2/Vista assuming that non-RFC1918 = 
> unfiltered/unNATed for the purposes of 6to4.
> Well, deeper problem is that they're using 6to4 on an end host I suppose 
> - it's supposed to be used on routers.

While I don't doubt that the 6to4 is broken in such circumstances, how 
many IPv6 content providers are using 6to4 addressing and not 2001:: 
addressing? 6to4 by default on xp and vista, in my experience, is only 
used if a) talking to another 6to4 address or b) there is no IPv4 
address available.

6to4 never seemed like a viable method for content providing, though its 
use at the eyeball layer is somewhat iffy given that it's primary use is 
for other 6to4 addresses. If prefix policies are altered to use it for 
2001:: addressing, problems start arising quickly.

A good example is that traceroutes through my he.net tunnel using 6to4 
source addresses do not get replies through he.net's network, presumably 
due to their routers not being 6to4 aware and having no route to 
respond. Responses pick up again after picking up a network such as NTT 
that is 6to4 aware. My 2001:: addressing works just fine the entire route.

I'm sure there's quite a few networks that aren't 6to4 aware, hindering 
6to4 connectivity to non-6to4 addresses.


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