Description of the problem

The link aggregation function is activated between two switches in a bureau. one of the ports takes the private line service configured by OSN3500's EGS44 and EGS2, and the other port is directly connected using optical fiber. the service is normal when the switches are activated for manual aggregation (LACP protocol is not enabled), but the service does not work when they are configured for static aggregation (LACP protocol is activated). the EGS4 single-board and the EGS2 The external port attribute of the single board is Hybrid, and the switch on the EGS4 side can receive LACP messages, while the EGS2 switch cannot receive LACP messages.

Alarm Message

Transmission No Abnormality Alarm

Processing

1. Since the service is normal when using manual aggregation, you can be sure that there is no problem with the transmission channel.

2. Compared with manual aggregation, the difference between static aggregation and manual aggregation lies in the use of the LACP protocol. Therefore, it is suspected that when static aggregation is used, the reason why the service does not work is that the LACP protocol message is not transmitted to the opposite end of the device.

3, LACP protocol is not with VLAN tags, port attributes set to Hybrid should not be a problem, suspected that egs4 single-board incoming ports do not LACP message through.

4, after confirming that egs4 single board supports LACP protocol, when the external port receives LACP messages will be sent to the CPU for processing and will not pass through the LACP message, in this case you need to set the port's "Entry Detection" function to "Disable".

5、After setting port "ingress detection", the static link aggregation service of the switch opens normally.

Root Cause

1. EGS4 board supports LACP protocol, when the external port receives LACP message, it will send it to CPU for processing and will not pass through LACP message, if you need to pass through LACP message, you need to set the "Ingress Detection" function of the port to "Disable". If you need to pass through LACP messages, you need to set the "ingress detection" function of the port to "disabled".

EGS2 single-board ports do not support LACP protocol and treat LACP messages as ordinary Ethernet messages, so LACP messages can be detected in one direction.

Recommendation and Summary

At the same time, we know that SSN5EFS0 also has this problem, and we need to pay attention to the "ingress detection" attribute configuration when we need to transmit LACP messages.

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