Description of the problem

Bureau O of country M, backbone layer OSN3500 equipment group 10G rate MSP ring network, access layer Metro1000 group 155M rate PP ring network. The central station A is on the MSP ring, and the access points B, C, D, E, etc. are on the PP ring. the EGS single board of A is connected to the EFT single board of B, C, D, E, etc. in EOS mode, and LAN service is opened; A is connected to the router equipment, and the WLAN and other wireless Internet access equipments are connected to the stations B, C, D, E, and each station is bound to 4 2M time slots. On a certain day, the customer finds that the WLAN service at stations B, C, D, and E is not available.

The T2000 network administrator checks the OSN equipment, and there are no abnormal alarms.

Processing

Since multiple access points are having problems at the same time, the following reasons are suspected:

1. SDH key node failure?

2. central station OSN equipment EGS board failure?

3、Failure of central station router equipment?

Root cause

N/A

Solution

1, T2000 check OSN3500, Metro1000, no hardware failure alarm, no business failure alarm, good performance.

2, digital communication engineers check the router, and found that Ethernet loops are formed on the network, forming network storms and blocking data services, and the loops occur below the router.

3, each access site B, C, D, E check the local hardware situation, no Ethernet port loopback was found, and station C has been removed.

4. Call the customer's transmission, WLAN, and digital communications engineers to discuss the Ethernet loopback problem. Ask the customer to recall whether there was any operation from the time of failure, when it happened, and before it happened. Some engineers feedback that a few days ago, the customer has dismantled all the equipment in station C because of the server room. It seems to be able to match up with the time of the failure.

5, the C station Metro1000 removal, and T2000 network management check, found that the station Metro1000 equipment grayed out, the network management can not log in. Between the upstream and downstream network elements in the ECC information can be seen directly. Further checking, found that the business path of station C still exists, that is, station C has been dismantled, but the upstream and downstream business of station C has not been deleted.

6. Therefore, the Ethernet service that should be up and down at station C and used for WLAN is not deleted because station C has been dismantled, and the service is looped back to the center bureau A on the SDH network. For the LAN service in this case, it is logically a switch, and its logical port ( VCTRUNK ) is looped back, so the services on "this switch" are disconnected.

Recommendations and Summary

It is traditionally believed that the 2M loopback of SDH equipment, which is an important means of determining faults, will not cause a fault because of the 2M loopback. Except for the SDH equipment Ethernet board hardware loopback, it will not cause the failure of Ethernet ringing.

Thinking carefully, SDH supports the establishment of LAN services in the form of EOS, and such LAN services, logically, are switches. If the bound 2M is looped back, the port " VCTRUNK " of the "logical switch" is looped back, which is the same as the result of the physical loopback of the physical switch, generating network storms and blocking services.

The technical information and SDH equipment troubleshooting procedures in this chapter are collected and organized by Shenzhen Optical Transmission Network Technology Company Limited ( www.opticaltrans.com), and please retain them! Our company specializes in the sale of Huawei SDH optical transmission equipment, SDH transmission equipment.