The TL;DR is that IPv4 means there's only 4 billion IP addresses, which modern 1-10Gbps backhaul links can ticker-tape through in a few minutes. IPv6's 18,446,7

The TL;DR is that IPv4 means there's only 4 billion IP addresses, which modern 1-10Gbps backhaul links can ticker-tape through in a few minutes. IPv6's 18,446,744,073,709,551,616 IP address limit will sadly make broad scanning utterly infeasible going forward until users have 1Tbit connections or so :( But for now we can do this with the v4 parts that are left: https://www.youtube.com/watch?v=nX9JXI4l3-E https://www.youtube.com/watch?v=nX9JXI4l3-E Also, some crazy person good-haxed a bunch of routers and modems back in 2012 and made http://census2012.sourceforge.net/paper.html http://census2012.sourceforge.net/paper.html (without access to fast connections and before the advent of masscan and other straightforward tools, too). Of note is that the "Unallocated" grey areas in the the analysis images are a curious illustration of how much less-full the IPv4 internet was just ~9 years ago.