If you are a BT Total Option 1 Broadband customer and have been having issues where some services like Xbox Live have not been working, then it is possible you have been taking part in the Carrier Grade NAT pilot (CGNAT) that BT Retail is running.
"The number of IPv4 internet address worldwide is running out, meaning that all ISPs must come up with a solution to keep new fixed broadband customers connected until IPv6 addresses become widely adopted.
BT is introducing a technology called Carrier Grade Nat (CGNAT) to help address this issue, which means that certain customers will share an IP address with up to nine other customers. This is the same as the standard practice for mobile broadband connections, using smartphones and tablets today.
We have decided that we will pilot this new technology with our Option 1 Total Broadband customers who on average use the internet least. We believe they are the least likely group of customers to experience any issues or disruptions due to CGNAT, which can interfere with complex online activities like hosting servers at home. We do not think these customers will notice any difference at all in their broadband performance, but if any of these customers did have any resulting issues, we would be happy to restore their connection to an individual IP address.
BT is also working to introduce IPv6 internet addresses during 2013, but customers will need both IPv4 and IPv6 addresses for the foreseeable future."BT Retail statement on Carrier Grade NAT pilot
Carrier Grade NAT means that an Internet connection gets a private range IP address, with the NAT hardware ran by the provider sharing the public IP address between a number of customers. This effectively means that people are behind a double NAT scenario, which breaks a number of services and also means that people wanting to run a small server or log into a network IP camera will find these are not accessible from outside their home network.
Plusnet was involved in a trial earlier in 2013 to look at the same thing. The suggestion is that while providers are getting ready to roll-out IPv6 they realise that many websites will still be running on IPv4 and therefore IPv4 is not going to vanish overnight.
BT has a FAQ on the Carrier Grade NAT to help with queries as the change is introduced to more Option 1 customers. The key to finding out whether you are already using the CG-NAT solution is to use a whois site that displays the Organistion that your public IP address is registered to, and if this is shown as CG-NAT then you are on the pilot already. If you are finding the CG-NAT to be a problem then by contacting BT support you can opt back to a public IP address for your connection.
Update 4th May To make it easier for those who want to opt out of the trial, this is the page to use to contact BT and request removal from the CG-NAT/IP Address Translation pilot.
Update 7th May We have double checked that the CG-NAT trial only affects Option 1 customers, and BT have confirmed this to be the case, there will be some BT employee's with Option 3 who are also on the trial. So if you are not on an Option 1 product and believe you affected by this CG-NAT/IP Sharing trial then do get in touch with us and we will investigate further.