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FAQ - Analysis on a Port Down Event on a 10GE Link

Publication Date:  2013-09-22 Views:  147 Downloads:  0
Issue Description

Version: N/A


Two 10GE ports are directly connected by optical fibers.


The link between the two 10 GE ports is unstable and ports often become down.
Handling Process

If configurations for the two ports are correct and the optical fiber and modules match, possible causes for a port down event are as follows:

1. Optical module los: indicates an optical module fails to receive optical signals. Check whether the transmit power of the remote end is normal. If yes, check whether the receive optical fiber of the local end is intact. If no, rectify the fault at the remote end.

2. PMA_los: indicates that the optical modules receive and transmit optical signals properly, but the PHY PMA layer fails to receive signals. This is often caused by an improper connection between an optical module and the device. Remove the optical module and clean its copper layer as shown in the following figure. If the problem persists, replace the optical module to check whether the problem are caused by a fault on the optical module or device hardware.



3. PCS_HBER: indicates a high bit error ratio at the PCS layer. When the 66/64B conversion is performed at the PHY PCS layer, the 66-bit SYNC header will be checked. If no 66-bit SYNC header exists, a synchronization error is generated. When the bit error ratio is greater than 0.0001, the PCS_HBER log is generated. This error occurs when the link quality is poor. Therefore, check the link quality.

4. PCS_unlock: indicates that the PCS layer is unlocked or cannot be synchronized. The PCS_unLock log is generated when the signal cannot be received for 16 consecutive times. Therefore, check the link quality.

5. Local_Fault: indicates that the local RS receives faults reported by the PCS layer. Upon receiving a local fault, the local RS stops sending normal packets. Instead, it sends remote error code, and inform the remote RS.

6. Remote_Fault: indicates a remote fault. The local end receives codes indicating a remote fault. Check why the remote port goes down.
Root Cause
Read corresponding registers to check the possible causes for a port down event and diagnose faults accordingly.
It is recommended that you check and record registers immediately after the lower layer software detects a physical port is down.