Customers fume as BT introduces IP sharing

BT engineer

BT trials Carrier Grade NAT as stop-gap between IPv4 and IPv6

BT is testing a system that would see broadband customers share IP addresses to avoid the looming IPv4 shortage.

The current IPv4 system is running out of space, and many ISPs and users aren't yet ready to switch to its successor, IPv6.

As a solution, BT is testing a technology called Carrier Grade NAT (CGNAT), which has already been trialed by Plusnet, an ISP owned by BT.

BT said its CGNAT trial would see a single IP address shared between up to 10 customers. "This is the same as the standard practice for mobile broadband connections, using smartphones and tablets today," BT added.

However, CGNAT means you can't set up port forwarding on your router, causing problems for anyone hosting a website or online game. The trial will be tested with customers on BT's "Option 1 Total Broadband" - it's lowest tier, "who on average use the internet the least", the company said.

We do not think these customers will notice any difference at all in their broadband performance

"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," BT said. "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."

However, it appears users are already noticing problems. "It's causing me a real headache, for a start none of my home servers are now accessible via the web, remote access to my PC is also blocked, and XBox Live requires NAT to be open to work correctly so has reduced multiplayer ability," said one user on the BT forums. "If BT has decided to roll out this solution I really hope that it realises the issues it'll cause its customers."

BT didn't say how many users would be affected or how long the CGNAT trial would run.

BT stressed that it's working to move to IPv6 this year, but said customers will need both IPv4 and IPv6 addresses "for the forseeable future".

(Thanks to PC Pro reader Richard Samson for the tip-off)

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