IPv4 exhaustion is on everyone’s lips: four out of five Regional Internet Registries have run out of freely available address space. The number of new allocations has stagnated, address markets have taken off, and address-sharing mechanisms (for example, Carrier-Grade NAT) are on the rise as operators try to squeeze the most out of their IPv4 address space. A RIPE Labs guest post by Philipp Richter asks what is really happening in the IPv4 address space? Measuring address space activity at scale is difficult. There’s really no single vantage point that can capture all the activity.