Huawei HG8245T Router Manual PDF (Setup & Configuration Guide)

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l

If the DHCP option82 function is enabled, check whether the device information carried

in a PPPoE packet is added by the OLT or by a user-side device during the authentication

on the BRAS.

–

If the device information is added by a user-side device, run the

dhcp-Option82 forbid-

forwarding service-portindexenable

command to allow the DHCP packet with the

device information added by the user-side device to pass user ports. Then, proceed to

Step 13

.

–

If the device information is added by the OLT (this is the default mode), there is no need

to proceed. Then, go to

Step 14

.

TIP

Run the

display dhcp l2 statistics

command to query statistics of the Layer 2 DHCP packet. In

statistics, "Number of received packets with untrusted option82" indicates that the OLT receives the

DHCP packet with the information added by the terminal.

l

If the DHCP option82 function is not enabled, go to

Step 14

.

Step 13

Check whether the service recovers to normal.

l

If the service recovers to normal, go to

Step 15

.

l

If the service does no recover to normal, proceed to

Step 14

.

Step 14

Record the results of the preceding steps in the form for reporting a fault, fill in the form

completely, and then submit the form to Huawei for technical support.

Step 15

The fault is rectified.

----End

5.8 Troubleshooting Cases of ONU Status Abnormality

5.8.1 Failure to Go Online of an ONT

The ONU going online failure is a fault in which an ONU fails to go online normally, but the

queried

Run state

of the ONU is displayed as

offline

by running the

display ont info

command

on the OLT.

TC-C6211 ONU Failure to Go Online Because of Too Large Fiber Length Difference

This topic describes how to troubleshoot the fault of ONU failure to go online.

Fault Type

Abnormal ONU connection

Keyword

Fiber length difference

ONU failure to go online

Fault Description

Network topology: Optical split level: two levels; level-one split ratio: 1:2; level-two split ratio:

1:16; backbone fiber: 2.2 km long; branch fibers: 500 m to 24 km long

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During deployment in an office, the receive optical power of all ONUs under two-level optical

splitters is normal but the ONUs fail to go online.

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 difference between the ODN Max. receive optical power and Min. optical power

exceeds the threshold.

Procedure

Step 1

Analyze the network. It is found that the distance between the farthest ONU and the OLT is over

20 km and the distance between the farthest and nearest ONUs is also over 20 km, as shown in

Figure 5-17

.

Figure 5-17

Too large length difference between branch fibers

Step 2

Plan the ODN again and connect the ONUs whose fibers are longer than 20 km to another PON

port. Then, ONUs normally go online.

Step 3

Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

Make sure that the difference between the largest ONU and the nearest ONU under a PON port

is smaller than 20 km.

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TC-C6212 ONU Registration Failure Because of Incorrect Fiber Connection

This topic describes how to troubleshoot the fault of ONU registration failure.

Fault Type

Abnormal ONU connection

Keyword

Fiber connection

ONU failure to register with the OLT

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 5-18

.

Figure 5-18

Fiber connection

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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.

TC-C6213 ONU Failure to Go Online Because of Not Clean Fiber Connector

This topic describes how to troubleshoot the fault of ONU failure to go online.

Fault Type

Abnormal ONU connection

Keyword

Fiber connector

ONU failure to go online

Fault Description

Network topology: Optical split level: one level; split ratio: 1:16; backbone fiber: 7 km long;

branch fiber: 1.2 km long

During deployment in an office, one ONU under the OLT fails to go online but other ONUs are

normal.

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.

Procedure

Step 1

Test the ONU receive optical power. It is found that the power is -21 dBm. The ONU receive

optical power should be -14 dBm based on the network topology. Therefore, the ODN branch

fibers may cause the failure.

Step 2

Locate the fault by segment. It is found that the endface of a segment of fiber is not clean. Clean

the endface and test the ONU receive optical power again. -15 dBm attenuation is obtained.

Then, the ONU goes online successfully.

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Step 3

Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

Before connecting a fiber, clean the fiber endface to prevent unnecessary attenuation caused by

dust.

TC-C6216 ONU Failure to Go Online Because of a Too Large Receive Optical Power

Difference Between ONUs

This topic describes how to troubleshoot the fault of ONU failure to go online.

Fault Type

Abnormal ONU connection

Keyword

Optical power difference

ONU failure to go online

Fault Description

Network topology: Optical split level: two levels; level-on split ratio: 1:2; a 1:16 optical splitter

connected to one channel and an ONT connected to the other channel

During deployment in an office, only one ONU goes online normally and all other ONUs fail

to go online. The receive optical power of the failed ONUs is small but is still larger than the

sensitivity.

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.

Procedure

Step 1

Test the ONU receive optical power. It is found that the receive optical power of the successful

online ONU is -7 dBm but that of other ONUs is -23 dBm.

Step 2

Calculate the range of the optical power of the entire ODN. The difference between the ONU

Max. receive optical power and the Min. receive optical power is (-7 dBm) - (-23 dBm) = 16

dBm, which is larger than 15 dBm. It is concluded that the large ONT optical power difference

causes the ONU with a low optical to fail to go online, as shown in

Figure 5-19

.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

392

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