It is reported that broadband users of a carrier access network at low speed, and they often drop offline.
1. Use PC to access network in ER, and the speed is very low.
2. Packets are discarded seriously at the link between NE40 and MA5200 through ping command, with packet loss rate of 63%; also, the interface of NE40 has CRC error which is increasing continuously, indicating that the link between NE40 and MA5200 is problematic.
3. The problem of packet loss persists although tail fiber is replaced.
4. Test the optical power of both MA5200 and NE40 respectively, and it is found that the optical power of MA5200 is very high, and it remains very high after adding an optical attenuator.
5. Use loopback to test the interfaces of both MA5200 and NE40, and the optical interface of NE40 is found problematic; the problem persists after teh optical module is replaced. At last, the interface is changed, and the problem is solved. It is located that the first optical interface on LPU of NE40 is problematic.