Outages on BT Wholesale are generally rare, but from looking at our BQM graphs for a number providers reveals a widespread issue affecting customers on providers like Zen, IDNet, Eclipse Internet and Plusnet around 11:15am today.
For some connections the fault appears to be resolved, but there are signs that some connections are still offline. In some cases an IP address that is not in the normal providers range has been assigned e.g. 172.16.3.223. This generally happens when you are connected to the local telephone exchange, but the link inside the BT Wholesale network that authenticates your login with your provider is broken.
AAISP Incidents Page contains more detail on the problem and is updated as the situation develops, which at 12:15 was that 20CN services are back, but 21CN is still offline for those affected.
For business users, it reflects the importance of keeping a backup connection, that uses a different wholesaler at least, e.g. a LLU service.
Update 1:35pm: It would appear that the majority of 21CN based connections are now back up and connected properly.