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One problem of ipv6 is proponents saying there are 2^128 addresses.

It's really hard to comprehend how many unusable ipv6 addresses are.

Having more than 2^16 hosts on a subnet is pretty much impossible. Sticking with "grain of sand" units, but using volumes all from wolfram alpha:

There's 2^80 usable IPs in the entire ipvv6 space, because of the /64 subnets. That's plenty. But for every subnet, that's 40 cubic metres unusable for every subnet, and a sphere 1mm wide of usable addresses.

My ISP give me a /48. I have under 30 addressable devices over 3 vlans. I'm using 40 cubic miles of space. A ratio of about 10 trillion:1

But that's nothing. The IP allocators are happy to give a bank a /16, or in your "grain of sand" measurements 30 times the volume of the moon.

To match my unused:used ratio of 10 trillion to one, chase manhattan would need 2^70 devices, which is billions of addresses per cell.

All the space that fanboys go on about is almost all unusable, so the extreme examples don't really help at all.






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