Question : ADSL Sub Interface down on router

I have been experiencing some issues recently at locations where we have routers with ADSL Interfaces as the primary interface. Basically it seems that the primary interface is up and does not appear to drop, but the sub interface is showing as down/down. I have tried reloading the device, but this does not appear to have resolved the issue.

Does any one have ideas as to what might be causing this issue and how to resolve the problem?

Answer : ADSL Sub Interface down on router

Did you have any joy with your service provider?