Maybe we should buy some of these and donate them to BT?
As strange as it seems to advertise a cable that "supports IPv6", it's very closely related to BT's problem.
When British Telecom states, as they did, that "BT currently supports IPv4 on it's[sic] Broadband products and does not support IPv6", that makes no more sense than saying "this cable does not support IPv6".
BT are paid to transport PPP data between the ISP and the end users. The contents of the PPP frames should be irrelevant — whether they be IPv4, IPv6 or anything else. Whether they're web traffic, email, IRC or anything else. Whether they're Russian, Polish, French, English or any other language... British Telecom are completely incompetent if they claim that some of these things are "supported" but others aren't. They are supposed to be providing a simple data transport — just like the cable — and they have no business caring about what gets carried over the transport.
The low-level transport really shouldn't care what's being carried across it, unless someone really went out of their way to fuck up. In fact it looks like Cisco did just that, on this occasion, and the muppets at British Telecom are too stupid to comprehend what's going on.
This is apparently a known Cisco problem, and I hear second-hand reports that it was actually expected to be fixed in the IOS version(s) that BT are using. If that's the case, Cisco get bonus fuckwit points — not only did they have such an inexcusable bug in the first place, but they also failed to fix it properly.
BT now say that they are "looking into this problem and will be holding a conference call with [their] suppliers". I wish them the best of luck with that. This particular supplier doesn't seem particularly competent either, judging by my recent experience of trying to report shameful security holes in some of their other products.
In the meantime, those subscribers lucky enough to be connected to Juniper's products instead of Cisco's should find that the service works just fine. BT use a mixture of both.