How to
troubleshoot Internet access failures encountered by some Point-to-Point
Protocol over Ethernet (PPPoE) users connected to an optical network unit
(ONU). The fault is caused by subscriber line interference.
Fault
Description
Error 678 occasionally occurs
when PPPoE users connected to an ONU perform dialup for Internet access. The
service can be temporarily restored after the user ports or the ONU is reset.
However, the fault recurs after the device runs for a period of time.
No control board fault, reset, or
loss of signal (LoS) alarms are generated on the ONU.
NOTE:
Card-type ONU devices,
such as the MA5616
and the MA5612,
support EIUA and EIUC service boards to provide fast Ethernet (FE) user ports.
Alarm Information
FE ports report port up and port
down alarms.
Possible Causes
- The control board is faulty.
- The uplink port is faulty.
- The upstream optical fiber is disconnected.
- The EIUA board is faulty.
- The subscriber line is faulty.
- Log in to the ONU remotely to check the running status of the device. It is found that the ONU is running properly without having reset repeatedly. This indicates that the control board, uplink port, and upstream optical fiber on the device work properly.
- Replace the EIUA board with another one delivered in the same batch. It is found that the fault persists, indicating that the fault is not caused by EIUA board problems.
- Run the display port statistics portid command to query the port statistics. It is found that the FE ports have received and transmitted a large number of cyclic redundancy check (CRC) error frames and conflict errors. This indicates that there is a subscriber line interference source around the device.
- Remove all network cables connected to the ONU and connect only one port to a PC to perform a test. It is found that the Internet access service is restored, indicating that the fault is caused by a subscriber line interference.
- Use a multimeter to measure the voltages between the device shell and lines 1, 2, 3, and 6 in the network cable. The measured voltages are all 100 V. Check the subscriber lines. It is found that the power cable of the device is bundled with the network cable. Remove lines 4, 5, 7, and 8 from the network cable because these lines produce strong electrical interference to the device. It is found that the service is restored.
- In this case, removing lines 4, 5, 7, and 8 from the network cable prevents the device from being affected by strong electrical interferences.
- The anti-interference abilities of EIUA boards manufactured after 2012 are improved a lot. When similar subscriber line problems occur, you are advised to replace the original board with one manufactured after 2012 to enhance the anti-interference ability of the device.
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