A new wireless carrier in London, Relish, has announced the deployment of a 4G LTE network. This network is running Carrier Grade NAT to get around problems of IPv4 scarcity. The company announced that they had completed rigorous testing of their CGN implementation and its effect on a range of applications, including online gaming, with no issues to report. Although readers of this blog will not be suprised at this, there are still efforts to demonize CGN through overblown fears of broken applications among those IPv6 advocates who understand the effect of CGN on IPv6 deployment. Understanding that CGN offers address sharing ratios that effectively moot the IPv4 exhaust problem, and that IPv4 exhaust is the only reason for IPv6, leads to the conclusion that successful CGN is the enemy of IPv6. In Relish’s case, as in the case of British Telecom’s CGN implementation, that tiny subset of the customer base which requires a real routable public IPv4 address can request or rent one. Thus every customer’s needs are met and the carrier does not have to acquire more IPv4 space to accommodate growth. Clearly CGN affects the IPv4 market through effects on sellers (who can transition to CGN and sell excess IPv4 inventory) and effects on buyers (who can turn up 1000’s of customers with 10’s of addresses). These effects drive down the price of IPv4 addresses. But if CGN is the ultimate solution preferred by the Internet organism, what is the long term outlook? Perhaps IPv6 transition never happens and the IPv4 network proliferates through CGN. What will the long term value of an IPv4 address be in that dim future?