IPv6 routing /48s

Christopher Morrow morrowc.lists at gmail.com
Wed Nov 19 22:37:53 UTC 2008

On Wed, Nov 19, 2008 at 5:05 PM, Jack Bates <jbates at brightok.net> wrote:
> 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 v6 addrs are just regular v6 addrs as far as the network is
concerned. if you put a 6to4 addr on your server you are saying that
you don't have native v6 transport to that host(s) and that you are
reachable via the 6to4 tunnel your host presumably has configured.

Content providers MIGHT put 6to4 addrs on their servers so that they
appear to be 'closer' to their clients, or so they might better
control the pathing between client/server... but that's really no
different than a non-6to4 addr as far as the applications and network
are concerned.

> 6to4 never seemed like a viable method for content providing, though its use

it doesn't seem clear that 6to4 buys the content provider much on
their side of the pipe, sure.

> 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.

6to4 is just an ip, 128bits long, but an ip... no differentiation is
made in the network for 6to4 vs 'normal v6'... unless someone's
putting up acls, or blackholing 6to4's /16, of course.

> 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.

can you explain this a little more? is it possible your v6 packets hit
something like 6pe inside HE and exit to NTT without hitting a

> 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.

'6to4 aware' doesn't compute...


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