IPv6 Ignorance

Mark Andrews marka at isc.org
Wed Sep 19 03:43:42 UTC 2012

In message <34689.1348009609 at turing-police.cc.vt.edu>, Valdis.Kletnieks at vt.edu wri
> --==_Exmh_1348009609_2143P
> Content-Type: text/plain; charset=us-ascii
> 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 o
> f
> 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....

But given that 6rd is DHCP this is all fixed with a little bit of programming.
It's not like it's new stuff anyway.  It also only has to be done once for
each address block.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org

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