Chapter 37. IPv6

You’ve no doubt heard the news stating that we will run out of IP addresses in the next half hour or so. Forgive my glibness, but I’ve been hearing this for 10 years or more.


As I was editing this edition for publication, the Number Resource Organization (NRO) reported that as of February 3, 2011, the free pool of IPv4 address space has been depleted. You can read all about it here:

There are a finite number of IP addresses, and they were horribly mismanaged when the Internet was young. Network Address Translation (NAT), Classless Internet Domain Routing (CIDR), and Variable Length Subnet Masks (VLSM) changed all that, and we got some breathing room. That was about 10 years ago, and the news is once again reporting that we’re about to run out of IP addresses. While everyone panics, I try to remind nervous CEOs that this is only an issue with publicly routable IP addresses. Still, given that there are a finite number of these addresses, we’ll hit the wall sooner or later.

IPv4 (the currently well-known standard) uses 32-bit addresses. This translates to 4,294,967,296 (4.2 × 109) IP addresses, though large blocks of them are considered either reserved or unroutable. For example, 16 million of them are contained within the private address space. Let’s say, for the sake of argument, that there are four billion public IP addresses. Are we really running out of them? Where have they gone?


If you’re not familiar ...

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