IPv6 Ignorance

Matthew Kaufman matthew at matthew.at
Mon Sep 17 15:18:52 UTC 2012


On 9/17/2012 5:28 AM, John Mitchell wrote:
> I think people forget how humongous the v6 space is...
>
> Remember that the address space is 2^128 (or 
> 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses) to put 
> the in perspective (and a great sample that explained to me how large 
> it was, you will still get 667 quadrillion address per square 
> millimetre of the Earth’s Surface.

Yes. But figure an average subnet has, what, maybe 5 hosts on it? (Sure, 
there's some bigger ones, but a whole lot of "my router, my PC, and 
maybe my printer" networks too.

So even if you could use all the top bits (which you can't, as many 
combinations are reserved), that's more like 92,233,720,368,547,758,080. 
And if you lop off the top three bits and just count the space currently 
assigned to Global Unicast, that's 11,529,215,046,068,469,760. Which is 
0.02 per square mm of the earth's surface. Or just over 2 per square 
centimeter.

Powers of two get big fast... but they get small fast too.

Matthew Kaufman



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