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There was a time when the link status of the optical port was very confusing to me. The same board was linked yesterday, but it is down today. When should I link and when should I link down?
Let me first describe the phenomenon. In the first state, if one of the receiving or sending fibers is broken, the link will go down; in the second state, the link will be down only when the receiving fiber is broken. The only difference between the two states is that the optical port auto-negotiation is configured, so let's take a look at the optical port auto-negotiation mechanism.
1. Both ends are set to auto-negotiation mode.
Both sides send /C/ code stream to each other. If three consecutive /C/ codes are received and the received code stream matches the working mode of the local end, it will return one to the other party. With the /C/ code of the Ack response, after the opposite end receives the Ack information, it is considered that the two can communicate with each other, and the port is set to the UP state
. 2. Both ends are set to forced mode
. After /I/ code stream, consider that the opposite end is the port that matches itself, and directly set the local port to the UP state.
Since the auto-negotiation state requires the ack response from the opposite end, so a fiber is unplugged alone, and one end cannot receive the code stream. , one end cannot receive the ack stream, it will link down; but in forced mode, as long as it receives a matching stream, it will link up. This is why, the link status of the optical port is sometimes expressed as R_link, and sometimes it is expressed as why the receiving and transmitting fibers are related.