[arin-ppml] Opposed to 2010-9 and 2010-12

On Wed, Oct 13, 2010 at 5:18 PM, Mark Andrews <marka at> wrote:
> In message <2376C0DA-2491-40D4-B509-8C643C507A61 at>, Owen DeLong write
>> On Oct 12, 2010, at 8:55 PM, Mark Andrews wrote:
>> > If you have a 2 disjoint /16's spead over, multiple pops, then you
>> > will have 2 6rd prefixes in use both with a IPv4MaskLen of 16.  Only
>> > one of these will be handed out to a specific customer.  If you are
>> > handing out /56's then the 6rdPrefixLen would be 40.  Each of these
>> > 6rd prefixes would be a /40.
>> For the handful  of providers that have only 2 prefixes, that may be.
>> For the vast majority of providers, the common practice (having more
>> than a couple of prefixes) is to map the entire IPV4 space onto
>> a customer prefix size (e.g. /56) yielding a need for a /24 (56-32)
>> prefix for the ISP. Since no ISP has a significant fraction of the
>> IPv4 space, much of that /24 is wasted.
> And doing what I suggests works for any number of prefixes.


In theory, it works for any number of prefixes. So there's this old
joke I heard:

What's the difference between theory and practice?
In theory, there is no difference.

Preparing and maintaining the configuration for one 6rd prefix is easy
enough. Two is not so bad. But a hundred? I wouldn't want to be the
guy stuck with debugging that morass.

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004