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Serious Packet Loss Caused by Mistakenly Inserting the FE Optical Transceiver into the Gigabit Optical Interface on the LPU A

Publication Date:  2012-07-27 Views:  91 Downloads:  0

Issue Description

Version information:
NE40E: host version V300R002C06B325; LPU type: CR52-10xGE-SFP, 10-port GE SFP optical interface LPU A.
A user is connected to interface 1/0/0 on LPU A of the NE40E. The user claims that the rate of accessing the Internet is slow and the packet loss is serious. 

Alarm Information


Handling Process

The troubleshooting process is as follows:
1. Check the logs of the NE40E. The logs contain no abnormal messages.
2. Check the interface state. The CRC is correct. The maximum bandwidth of the interface is 1 Gbit/s, but the maximum bandwidth of the optical transceiver is 155 Mbit/s.
The configuration of the optical transceiver does not match that of the interface, and therefore packet loss occurs. 

Root Cause

The possible causes are as follows:
1. Fiber path is of low quality.
2. Optical interfaces at the user side and the NE40E run in different modes.
3. Optical transceiver fault.
4. Client fault. 


To sum up,
1. The FE optical transceiver and the 155 Mbit/s POS optical transceiver are interchangeable on the NE40E. If you insert an optical transceiver into the GE interface, the maximum bandwidth of the optical transceiver is155 Mbit/s, not 100 Mbit/s.
2. If you insert an FE optical transceiver into the GE interface on the LPU A of the NE40E, the NE40E does not display an alarm, the state of the interface and protocol is normal, and the service can be delivered except that serious packet loss occurs. Note that the FE optical transceiver looks exactly like the GE optical transceiver.