Activists are again lobbying for more than 250 million unused IPv4 addresses to be released for use, potentially tackling the IPv4 exhaustion problem. However, the proposal has been tried and failed before, and again faces formidable opposition. The unused addresses are known as the “240/4” block and comprise most of the IPv4 addresses from 240.0.0.0 to 255.255.255.254 – a space that encompasses upwards of 268 million addresses, or about six percent of the entire IPv4 number space. For some pers...