IPv4 address shortage
Another proposal was to assign the class E IPv4 addresses, which are 240.0.0.0 - 255.255.255.254, for use on the public Internet. These addresses are currently reserved for "future" or "experimental" use. This would only add about 268 million addresses to the IPv4 Internet - not enough to prevent running out of addresses. Another issue with this approach is that most operating systems (including Windows), routers, servers, and other equipment block these addresses, as they assume that they are invalid. Using these addresses would require updating every computer, router, and server to recognize them as valid - effort which would better be spent on deploying IPv6.