Spain, Dr. Jeffry A. spainj at countryday.net
Sat Nov 19 19:23:19 UTC 2011

```If you are concerned about a repeat of the IPv4 address exhaustion problem, this is a different issue. The 64-bit IPv6 interface identifier has to be unique for each device on an IPv6 subnet. Even if you choose the IIDs randomly for, say, 1000 devices, the probability of a duplicate is very low. There are actually 62 bits available, not counting the universal and group bits. The probability is 1 - ( 2^62 x 2^62-1 x 2^62-2 x ... x 2^62-999 ) / ((2^62)^1000) = 1.08 x 10^-13. See "Brithday Problem" http://en.wikipedia.org/wiki/Birthday_problem.

IPv6 address exhaustion would be related to the remaining 64 bits of the address, which identifies the subnet. Ignoring for the moment that not all of this is unicast address space, you still have on the order of one subnet per square centimeter of the earth's surface. I guess this may become a problem, for example, when we are assembling things like houses and cars out of nanobots.

-----Original Message-----
From: bind-users-bounces+spainj=countryday.net at lists.isc.org [mailto:bind-users-bounces+spainj=countryday.net at lists.isc.org] On Behalf Of ?? ??
Sent: Saturday, November 19, 2011 1:48 PM
To: bind-users at lists.isc.org

> Oh, and given you've got 64bits to play with, so long as your random
> numbers are up to scratch no need to worry about collisions.  You'ld
> need to be assigning millions of addresses before you ran into that problem.

Not to be an ass and this is likely a decade too early, but... this is
direct echoes of what I heard 20 years ago.

Does systematic thinking belong in /32+ IPv6 addressing or is it in fact
safe to just random it all away willy-nilly?
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