IPv6 Ignorance

Valdis.Kletnieks at vt.edu Valdis.Kletnieks at vt.edu
Tue Sep 18 23:06:49 UTC 2012

On Tue, 18 Sep 2012 18:18:28 -0400, William Herrin said:

> In http://lists.arin.net/pipermail/arin-ppml/2010-September/018180.html
> I complained about mapping the full 32-bits of IPv4 address into an
> IPv6 prefix. You responded, "You say that like it's somehow a bad
> thing," and "I'm simply not seeing a problem."
> Have you come around to my way of thinking that using 6RD with a full
> 32-bit IPv4 mapping is not such a hot idea?

They're not in contradiction - you want a /28 so you can do 6RD, ARIN should
let you do that.  You want a /28 so you can do a non-6RD network plan, you
should be allowed to do that too.

But you don't get to deploy 6RD, and then complain that you don't have enough
bits left when you try to do a non-6RD design.

Or you could be a bit smarter and realize that you probably only actually *need*
to use 16 or 20 bits of address for 6RD mapping and leave yourself 16 or 12
for other uses.  AS1312 has 2 /16s, so we only need to map 16 bits of address
and one more to indicate which /16 it was and the rest can be implicit.  Which of
course still loses if you have more than a /8 or so, or if you have 1,495 little
prefixes that are scattered all over the /0....
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