Symptom: Physical layer of E1-F port of AR28-40 is not up.
Topology: AR28-40----2M----ROUTER. E1-F port of the router has five timeslots including 1, 3, 4, 5, and 7. E1-F port of AR28-40 uses 1-31 timeslots by default.
Change the configurations for E1-F of AR28-40 and encapsulate the timeslot of 1, 3, 4, 5, and 7, solving the problem.
The problem is caused by difference in timeslot configurations of equipment at both sides of E1 link.