The prediction that one day we will run out of IPv4 addresses is often seen as a warning with little substance to it, and many providers appear to see little point in implementing IPv6 at this time. The predictions though may becoming true, as Plusnet moves to start a Carrier Grade NAT trial, to help conserve the number of IPv4 addresses they need.
"We need a bit of help with some testing over the next few weeks. As many people will probably know there's a finite number of IP addresses in the world and there aren't many left. In order to ensure that people have access to the Internet during the transition to the new world of IPv6 ISPs like ourselves are looking at options including Carrier Grade NAT. Even if the world switched on IPv6 today there would still be people and applications that don't work under IPv6, some games consoles for example. As such everyone will still need an IPv4 address for the foreseeable future."Plusnet seeking customers to trial carrier grade NAT
Carrier Grade NAT has been used by mobile operators in the past, and the result for ADSL and fibre connections is that the router in the home would be handed a private network IP address. This creates several problems (1) services that rely on port forwarding/UPnP will not work (2) if the private IP range is the same as routers LAN side this can cause routing issues (3) services like VPN that use a public IP for security checks may fail.
"All ISPs should be providing proper IPv6 first, and using NAT purely as a stop-gap. This will allow innovation to continue and use the end to end design of IP, and it will mean services using IPv6 will 'just work'.
At AAISP we have been providing IPv6 for over 10 years now, and we expect to be able to provide at the very least a single fixed IPv4 address per line without carrier grade NAT for many years to come."Comment from Adrian Kennard of AAISP
Hopefully Plusnet will implement IPv6 swiftly, the BT Wholesale platform supports dual stack IPv4 and IPv6 connections already. None of the major broadband providers in the UK support IPv6 yet, and while there is no compelling IPv6 application as yet, by starting to switch now the providers can avoid a big confusing rush in a couple of years.
One of the common problems for the consumer is that some hardware, particularly current generation games consoles do not support IPv6, if the next generation consoles do then the problems of configuring NAT may at last be consigned to history, but only if broadband providers support IPv6.
A slight chicken and egg situation does exist and that is support for IPv6 in consumer routers, but the situation is improving and the buying power of the larger providers will quickly change that.
Update 4pm: Adrian Kennard has written a longer blog article going into greater depth about the problems carrier grade NAT can introduce.