Problem Description

At an overseas bureau point, Huawei NE40E-X3 digital pass-through switches are networked via SDH transmission equipment products, with the transmission four equipment topology as two chains and the digital pass-through four switches topology as a ring structure. The two ends of the bureau were two S6506 switches and two S3528 switches. After the industry soft engineers start the STP protocol on the digital communication switches, they find that they are divided into two domains. Checking the switch port counts, it is found that there is packet loss.

Alarm messages

There are no related alarms on the transmission device.

Processing

After communicating with the engineers, we learned that the broad STP protocol has three modes : MSTP (Multiple Spanning Tree Protocol), RSTP (Rapid Spanning Tree Protocol), and STP (Spanning Tree Protocol), which are theoretically compatible with each other, i.e., STP can be used to transmit RSTP and MSTP, and RSTP can be used to transmit MSTP.

However, checking the OSN products related characteristics document, our OSN products currently only support RSTP, STP, and when realized, can not be docked with MSTP, for OSN data single board inherent defects.

So far, after coordinating the field engineer to change the STP protocol mode of the docking switch to RSTP, the fault disappeared.

Root Cause

Since there is a clear record of sending packets but no record of receiving packets on the digital communication equipment. It can be basically determined that the relevant packets are discarded on the transmission equipment.

Recommendations and Summary

Due to the native compatibility of MSTP, RSTP, and STP, the STP protocol mode of the digital communication equipment is MSTP by default, but the OSN equipment data veneer implementation has the relevant defects, which can not transmit the MSTP protocol message, so it is necessary to change the relevant configuration of the docking switch. When explaining to the customer, you can blur the compatibility between MSTP and RSTP and emphasize that our equipment does not support MSTP (Multiple Spanning Tree Protocol) to avoid customer backlash.