We are seeing MTU issues on some 21CN lines this morning where lines are unable to pass more than 1462 byte IP packets. It isn't affecting all lines, and the common factor appears to be that they are on ACC-ALN1 BRASs in London, but not all lines on those BRASs are affected. We have reported the issue to BT Wholesale and they are investigating the issue.
BT have now raised an incident and are investigating.
This has been fixed. We've been speaking to some network guys at BT this evening and helping them find the fault.
BT fixed this last night. We believe BT had equipment in the network that was miss-configured.