NAT66 and the subscriber prefix length

Tim Durack tdurack at gmail.com
Tue Nov 18 13:59:53 CST 2008


On Tue, Nov 18, 2008 at 2:33 PM, Crist Clark <Crist.Clark at globalstar.com>wrote:

> >>> On 11/18/2008 at 11:03 AM, "Tim Durack" <tdurack at gmail.com> wrote:
> > On Fri, Nov 14, 2008 at 2:28 PM, Mikael Abrahamsson <swmike at swm.pp.se
> >wrote:
> >
> >> On Fri, 14 Nov 2008, michael.dillon at bt.com wrote:
> >>
> >>  Not long ago, ARIN changed the IPv6 policy so that
> >>> residential subscribers could be issued with a /56
> >>> instead of the normal /48 assignment. This was done
> >>> so that ISPs with large numbers of subscriber sites
> >>> would not exhaust their /32 (or larger) allocations
> >>> too soon. Since these ISPs are allowed to assign
> >>> a /56 to residential subscriber sites, their initial
> >>> IPv6 allocation will last a lot longer and they won't
> >>> have to apply for an additional allocation while
> >>> everyone is getting up to speed with an IPv6 Internet.
> >>>
> >>
> >> We returned our /32 for a /25 (with /22 being reserved) and current plan
> is
> >> to hand out /48s to everybody (unless they need even more space, then
> >> they'll have to apply).
> >>
> >> So, doing /56 to end users just because you happen to have a /32 right
> now
> >> sounds like a bad plan, it doesn't take that many hours to get a larger
> >> space if you can justify it (which wasn't that hard for us).
> >>
> >> We received our /32 (as a /35 I think) back in 2000 or so, policy has
> >> changed since then, with RIPE it's not that hard to get a much larger
> space
> >> with a long term growth plan. My hope is that we'll make do with this
> /22
> >> space for at least 5-10 years (67 million customer /48s is quite a lot),
> >> unless something really big happens, and then we'll just have to get an
> even
> >> larger space.
> >>
> >> So message should be that /48 to end users is the way to go, and this
> >> should suit residential and SME market without any additional
> administrative
> >> overhead depending on customer size.
> >>
> >> --
> >> Mikael Abrahamsson    email: swmike at swm.pp.se
> >>
> >>
> > This raises questions for me: we are a mixed enterprise/campus
> environment.
> > Recently got a /45 assigned, so we have a /48 per site (it was some work
> to
> > convince ARIN that fancy subnetting to make a /46 stretch a little
> further
> > made no sense.)
>
> A /45? I thought all allocations were on nibble borders for
> IP6.ARPA considerations.
>
>
2620:0000:/23 is PI. ARIN makes assignments to end user sites of anywhere
between /48 and /40, depending on your justification.

ARIN wanted to give us a /46 for 5 sites, which made no sense. We pushed
back for a /45, and that's what they gave us. Still not convinced it's going
to be enough.

Tim:>



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