ATM interface state error
Symptom
The interface state of ATM is DOWN.
Solution
Make sure the optical fibers are correctly connected to ATM interface. There should be two optical fibers, one for receiving information and one for sending information. The two are not exchangeable. If they are wrongly connected, the interface state of ATM cannot be UP.
If two routers are connected back-to-back, check if neither of the two ATM interfaces enables internal transmission clock. By default, routers use line clock. If two routers are connected back-to-back, one of them should be configured as internal transmission clock with the clock master command.