In the RTN910/950 V1R1 (5.76.01.33) with the link configured as 1+1 HSB, the near end taking the clock from the E1-1, the far end from the Stand By IF has the first priority and the Main IF working when a BER test is running it shows synchronization alarms.
Set the Main IFU as the first clock priority.
Taking into account that the IFU and the CXPAR board have an independent clock unit and that the controller board clock synchronizes with the IF board clock unit, the RTN first clock priority port/board must be the same as the active port/board.
After some tests ran with the same result we procedure to verify the Following:
1. Clock priority of the BER tester: It was configured as internal
2. Clock priority from the near end side: It was configured with the E1-1 to E1-4
3. Clock status from the near end side: it was synchronizing from the E1-1
4. Clock priority from the far end side: It was configured with the 5-IFU (Stand By)
5. Clock status from the near end side: it was synchronizing from the 5-IFU
6. Far end IFU active board: It was working with the MAIN board
Always configure both IFs in the priority list of the RTN and configure the main IF as first priority.