As of January 1, 2011, the number of unused IPv4 addresses stands at 495.66 million. Exactly a year earlier, the number of available addresses was 721.06 million. So we collectively used up 225.4 million addresses in 2010. 242 million, really, if we ignore the unusual circumstance that Interop gave back nearly 17 million addresses.

At first glance, this suggests that we have two more years of IPv4 addresses left. But it’s not that simple: Asia is almost certainly going to run out before year end. And that means really running out, as in: sorry, no addresses for you.

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