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BFD Session Flapping Occurs Because the Traffic Rate Exceeds the Specification of an NE40

Publication Date:  2013-01-08 Views:  119 Downloads:  0
Issue Description

As shown in the following networking diagram, an NE40E that functions as a PE and an NE40E that functions as a CE are attached to the UMG. BFD is deployed on the transmission devices between the two NE40Es. The BFD session flaps frequently on the NE40Es during the peak hours from 21:00 to 23:00 every day, which causes frequent master/backup VRRP switchovers.


Handling Process

1.         Since the problem occurs only during the peak hours and the transmission bandwidth is sufficient, the transmission quality cannot be the cause for the problem. The on-site Huawei technical support personnel focus on the processing of BFD packets during the peak hours.

2.         They check the BFD session flapping logs on the NE40Es and find that DetectDown is displayed in the Diagnostic field in the BFD logs. This proves that the processing of the BFD packets is affected.

3.         Then they monitor the traffic on the interfaces of the two NE40Es during the peak hours and find that the traffic rate on the LPU in slot 2 has reached 2.2 Gbit/s. If the peak burst rate exceeds the bandwidth on the interface, packet loss will occur.

4.         They continue to observe the BFD session flapping for several days and find that the traffic rate on the LPU in slot 2 keeps about 2.3 Gbit/s during the peak hours every day. Therefore, they locate the problem on the LPU in slot 2.

5.         The problem is resolved after the traffic on the LPU in slot 2 is load balanced to LPUs in other slots for transmission.

Root Cause

The traffic rate on the LPU in slot 2 exceeds the specification, causing the LPU processing performance to deteriorate. As a result, the packets are lost.


Load balance the traffic to different LPUs for transmission to ensure that the traffic rate on an LPU does not exceeds the specification.