Problem description

A bureau, network A to B site has two different routes of the link, the two stations using N1EFS0A single board to open point-to-point services, a total of 8 VC12 bandwidth, 1-4 VC12 and the latter 5-8 VC12 to go to a different route, in the case of one side of the routing interruptions, the Ethernet is not interrupted, in the configuration of the first 4 VC12, the business is normal, will be added to the binding of the 5-8 VC12 after the EFS0 ETH_LOS alarm is reported on EFS0 after adding binding to 5-8VC12, and it is necessary to investigate the cause.

Alarm message

ETH_LOS

Process

1, configure 1-4 VC12, business is normal, there is no ETH_LOS alarm, ruled out the external port and switch port rate mismatch, network port and network port failure, due to the addition of 5-8 VC12 reported ETH_LOS, suspect that there is anomalies in the 5-8 VC12, will be 1-4 VC12 to bind the 5-8 VC12 to VCTRUNK1, business is also normal, there is no ETH_LOS alarm, need to troubleshoot the cause. VCTRUNK1, the service is normal, there is no ETH_LOS alarm, to rule out the existence of abnormal 5-8VC12, and then 1-8VC12 are bound at the same time, ETH_LOS generated, the service is not available, at this time and the switch side to confirm that the switch side port physical down, the reason is that spanning tree detects the loop will be the port physical down.

2. Check the SDH service side, the path is normal and there is no loop.

3, check the Ethernet service configuration of the two stations, both stations are configured for Ethernet LAN services, 1-4 VC12 binding VCTRUNK1, 5-8 VC12 binding VCTRUNK2, the external port using PORT1, are added to the same VB of the same VLAN at the same time, the use of the 802.1q protocol, the 801q protocol based on the VLAN + MAC Learning and forwarding, in the case of receiving broadcast frames or unicast unknown frames from the customer side, it will broadcast the data to all other interfaces in the same VLAN except the incoming interface of the message, so the broadcast frames will cycle back and forth between the two stations non-stop, resulting in loops, while the switch side starts the Spanning Tree (MSTP) protocol, which detects the loops and turns the ports down, so the transmission side ETH_LOS

alarm.

4, according to business requirements, in the case of a link failure, half of the time slot is not available, the Ethernet can not be interrupted, this requirement can be realized using the LCAS function, will be the two stations of the 1-8VC12 are bound to VCTRUNK1, select the Ethernet single board - Ethernet Configuration - Ethernet Interface Management: in the internal port of the LCAS tab, the LCAS function will be enabled VCTRUNK1, Ethernet is normal, and the transmission side ETH_LOS alarm is reported. The Ethernet is normal and the ETH_LOS alarm disappears.

Root cause

When configuring Ethernet LAN service on the transmission side, two VCTRUNKs are added to the same VLAN of the same VB between two stations, resulting in a loop on the transmission side, and MSTP Spanning Tree is enabled on the switch side by default, and Spanning Tree detects the loop and downs the port, resulting in an ETH_LOS alarm on the transmission side.

Solution

Bind 1-8VC12 to the same VCTRUNK, and enable LCAS function, so that the Ethernet service will not be affected in case of partial time slot failure.

Suggestion and Summary

1, LCAS function can dynamically adjust the bandwidth, you can use this function to protect different routes.

2、Switching side default MSTP function is on, and under default configuration, BPDU message does not carry VLAN, after VLAN division configuration, MSTP protocol BPDU message is with VLAN.

This chapter of related technical information and SDH equipment troubleshooting process by Shenzhen Optical Transmission Network Technology Co. Huawei SDH Optical Transmission Equipment,SDH Transmission Equipment Sales