> I feel like this blog does not accurately describe how large the ipv6 address space even after accounting for it being reduced by 2^64 for the host portion of

> I feel like this blog does not accurately describe how large the ipv6 address space even after accounting for it being reduced by 2^64 for the host portion of the address. One way of thinking about it: * Stars in the Milky Way: 400 Billion * Galaxes in the universe: 2 Trillion So (4x10^11)x(2x10^12)=8x10^23 stars in the universe. * Size of IPv6 address space: 3.4x10^38 Find the ratio between addresses and stars: * 3.4x10^38 / 8x10^23 IPv6 offers about 430 trillion times more addresses than estimated stars in the universe. From Tom Coffee's presentation "An Enterprise IPv6 Address Planning Case-Study" * https://www.youtube.com/watch?v=7Tnh4upTOC4 https://www.youtube.com/watch?v=7Tnh4upTOC4 Perhaps in more human terms: on the surface of the Earth (including oceans), there are 8.4 IPv4 addresses per km^2. Not counting the oceans, that would be 28 IPv4 addresses per km^2 land. IPv6 gives 10^17 addresses per mm^2 (yes, square millimeter). In terms of volume, 10^8 IPv6 addresses per mm^3 throughout the Earth. Another way of looking at it: *math property: x^y = x^(a+b) = (x^a)x(x^b) * IPv4 addresses are 32 bits (2^32) * 2^32 ~ 4.3 billion * So the IPv4 Internet has ~4.3B devices on it * IPv6 subnets are 64 bits, /64 (2^64) So, an IPv6 2^64 subnet is the same as (2^32)x(2^32), which means (4.3B)x(IPv4 Internet). I.e., a single IPv6 subnet can hold the equivalent of four billion (IPv4) Internets.