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Re: IPv6 end user addressing
From: William Herrin <bill () herrin us>
Date: Sat, 6 Aug 2011 14:28:41 -0400

On Fri, Aug 5, 2011 at 12:17 PM, Brian Mengel <bmengel () gmail com> wrote:
In reviewing IPv6 end user allocation policies, I can find little
agreement on what prefix length is appropriate for residential end
users.  /64 and /56 seem to be the favorite candidates, with /56 being
slightly preferred.

Hi Brian,

/64 is *strongly* discouraged. I'd go so far as to say that when we
look back 3 years from now, anybody who assigned /64's to end user
networks will be considered short-sighted bordering on foolish. Assign
a /128 if you know the downstream is exactly 1 host (not a LAN, not a
PC with virtual machines, exactly one computer) or else assign at
least a /60.

I am most curious as to why a /60 prefix is not considered when trying
to address this problem.  It provides 16 /64 subnetworks, which seems
like an adequate amount for an end user.

Every time someone needs more than the standard assignment, you have
to make a custom assignment with the manpower cost to make it and
maintain it. This will happen often with /64, occasionally with /60
and rarely with /56.

On the flip side, /56 allows for 16M end-users in your /32 ISP
allocation. After which you can trivially get as many additional /32's
as you want. Is there any reason you want to super-optimize to get
268M end-users squashed in that /32?

Bill Herrin

William D. Herrin ................ herrin () dirtside com  bill () herrin us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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