IPv4 addresses are 32-bit while IPv6 addresses are 128-bit. Customers can get a /64 allocation of IPv6 addresses provisioned to every one of their SoftLayer servers. A /64 block of IPv6 addresses contains 18,446,744,073,709,551,616 distinct addresses. The entire IPv4 address space is 4,294,967,296 distinct addresses.
It's easy to get lost in a sea of numbers when you start talking about IPv4 and IPv6 address space. With the exhaustion of IPv4 address space and the big push toward IPv6, everyone's talking about address blocks, usage justification and dual stack compatibility, but all of those conversations presuppose a certain understanding of why IP addresses are the way they are. Someone can say, "The IPv6 pool is exponentially larger than the IPv4 pool," but that statement needs a little context when you hear that providers like SoftLayer are provisioning a free /64 IPv6 allocation of 18,446,744,073,709,551,616 addresses to a single server. If the entire IPv4 pool on the Internet is 4,294,967,296 addresses and we're giving away that many IPv6 addresses to a single server, a simple question logically follows: Are the Internet authorities being irresponsible when they're allowing such huge numbers of IPv6 addresses to be assigned to individual servers without a demonstrated need for that many addresses?
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