How to Troubleshoot Internet Access Failures

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.

Procedure

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

Suggestions and Summary

• 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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MA5603T: TC-C6212 ONU Failure to Go Online

TC-C6212 ONU Failure to Go Online Because of Incorrect Fiber Connection. This topic describes how to troubleshoot the fault of ONU registration failure.

Fault Description

Network topology: Optical split level: one level; split ratio: 1:16; backbone fiber: 3.2 km long; branch fiber: 600 m long

During deployment in an office, an ONU fails to register with the OLT. The ONU receive optical power is 1.27 dBm and its transmit optical power is -15.9 dBm. The fault persists after system restart or soft system reset.

Alarm Information

None

Possible Cause

l The ONU receive optical power is larger than the overload optical power.

l The ONU receive optical power is smaller than the sensitivity.

l There is abnormal attenuation on ODN lines.

l The fiber is incorrectly connected.

Procedure

Step 1 Test the ONU receive optical power. The ONU receive optical power is -15.9 dBm, which is within the normal range.

Step 2 Perform a remote query. It is found that the ONU should be connected to another PON port.

Then, it is determined that the optical fiber is incorrectly connected.

Step 3 Confirm the connection on site. It is found that the optical fiber is incorrectly connected, as shown in Figure 7-2.

Figure 1 Fiber connection

Step 4 After the fault is rectified, services recover.

Step 5 Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

Identify different ports using labels in engineering and manage the ports differently to prevent incorrect connection.

Customers interested in purchasing Huawei MA5600 or the price, please refer to below links:

MA5616

Huawei MA5612