Description of the problem

A highway has five toll stations, A, B, C, D, and E. The five stations use Huawei OSN1500B equipment to form a 622M-rate SNCP ring, and the B, C, D, and E stations on the ring carry video surveillance services, which are aggregated at the A station by creating LAN services.

One day, the customer wants to break the ring to go to the point of the E site from the ring to pull out, forming a 4-point SNCP ring, the site breaks the ring to go to the point, found that the B, C, D station business is all broken.

Alarm Information

No abnormal alarm

Processing

The service of the whole network is interrupted, and there are two reasons: 1) Hardware failure or docking failure at site A. 2) Loop formation.

1、Restore the network before the operation, the service is normal, to rule out the possibility of site A hardware failure and docking failure.

2. After going to the point, the service is interrupted again.

3. Enable the VCTRUNK loop detection function of the converged Ethernet board, and find that ETHOAM_VCG_SELF_LOOP is reported on the VCTRUNK of the corresponding E-site, which is sure that the service is interrupted because of the formation of a loop after going to the point.

Root cause

As shown in the figure below: Normal A-E service is shown in the left figure, because the A-E site service was not deleted before the de-pointing operation, the service sent from the A site to the E site was received by the E site after the de-pointing operation (as shown in the right figure), resulting in the generation of a loop and the formation of a broadcast storm.

Solution

In the Ethernet Huawei OSN1500 LAN service at site A, delete the VCTRUNK corresponding to site E from the filtering table, and the service can be resumed.

Suggestion and Summary

To avoid this kind of problem, all the services landed at site E must be deleted before operation (the whole circuit is deleted, not only the cross of site E is deleted).

The relevant technical information in this chapter and the SDH equipment troubleshooting process is collected and organized by Shenzhen Optical Transmission Network Technology Company Limited ( www.opticaltrans.com), reproduced and retained! Our company specializes in Huawei SDH optical transmission equipment, SDH transmission equipment sales.