The problem that the optical module can receive the luminous state but it is down.

preamble

This is recently encountered a relatively embarrassing thing, because our server is deployed in a server room, the business network is to take the fiber optic transmission, the server room side of the notification has been configured, so that my side of the tuning through the business network, the results of the remote debugging found that it does not work at all!

Status of the issue

• Physical port down status
• Optical modules receive light normally

1
 Current Tx bias(mA)                  :15.00
2
 Default Tx bias High Threshold(mA)   :90.00
3
 Default Tx bias Low  Threshold(mA)   :0.00
4
 Current Rx Power(dBM)                :-4.49
5
 Default Rx Power High Threshold(dBM) :1.00
6
 Default Rx Power Low  Threshold(dBM) :-27.96
7
 Current Tx Power(dBM)                :-6.38
8
 Default Tx Power High Threshold(dBM) :-1.50
9
 Default Tx Power Low  Threshold(dBM) :-10.50

troubleshooting

Initially, it was to arrange for a resident colleague to assist in the server room, and his feedback was that the fiber optic cable was not illuminated, and I mistakenly thought that the server room had made a mistake in connecting our fiber optic cable, and then looked for feedback from the person in charge of the network in their server room, including whether the fiber optic cable was using single-mode or multi-mode?Is it single-mode or multi-mode?If single mode is it SC or LC type?How many G’s is the module and what is the port rate?With our equipment connected to the interface mode is routing or switching and so on a series of problems, feedback confirmation are no problem, then where is the problem?We have ruled out physical link problems between the interconnection, then it is the logical level of the problem, then first locate the interface negotiation, the interface negotiation type is automatically changed to mandatory, the interface state will become UP state.

method settle an issue

Enter the device to change the interface negotiation mode

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<USG6300E>system-view
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[USG6300E]interface GigabitEthernet 0/0/1
3
[USG6300E GigabitEthernet 0/0/1]undo negotiation auto

Remember to save the configuration when it’s done

Ex post facto analysis of causes

This kind of port can’t communicate properly is the problem caused by the different negotiation modes between devices!The problem is that one end is set as self-negotiation, one end is set as forced, the self-negotiation end sends /C/ code stream, the forced end sends /I/ code stream, the forced end can’t provide the negotiation information of this end to the other end, and can’t return Ack answer to the other end, so the self-negotiation end is DOWN, but the forced end can recognize the /C/ code, and think that the other end is the port that matches with itself, so it directly sets the port of this end in UP state, but both ends are set to forced mode, both sides will send /I/ code stream to each other.state, but both ends are set to the forced mode, both sides will send /I/ code stream to each other, one end receives the /I/ code stream, thinks that the opposite end is the port that matches with itself, and directly sets the port of this end to UP state.