Re: NAT66 and the subscriber prefix length

From: Tim Durack (no email)
Date: Tue Nov 18 2008 - 14:03:11 EST

  • Next message: Geoff Huston: "Re: IPv6 routing /48s"

    On Fri, Nov 14, 2008 at 2:28 PM, Mikael Abrahamsson <>wrote:

    > On Fri, 14 Nov 2008, 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:
    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.)

    We have also started offering residential Internet to those living on
    campus, which has been very popular (no suprise.) If I'm expected to assign
    a /48 per residential user, I'm already out of address space. Should I be
    requesting a /32? Is it acceptable to carve the /32 up a little for IPv4
    style multi-homing?

    I'd rather come to terms with this now before I do any meaningful


  • Next message: Geoff Huston: "Re: IPv6 routing /48s"

    Hosted Email Solutions

    Invaluement Anti-Spam DNSBLs

    Powered By FreeBSD   Powered By FreeBSD