Topology: NE80-transmission device-NE80
Two NE80s are connected through 155M POS and transmission device is placed between them. And then it is found that the physical layer is up, but link layer is down.
Link of NE80 POS is off.
1. Through loopback test of the fiber and it is found that optical channel connection is correct.
2. Use optical power meter to test attenuator and it is found that the attenuator is in normal range.
3. Check POS interface configuration of two NE80s, the link layer protocol of both ends is PPP, MTU 4470, frame format SDH, cost byte C2 consistent, but the clock is master; change one side as slave and then the problem is solved.
1. Optical channel is unreachable.
2. The attenuator is too serious.
3. POS interface configuration is problematic.
1. When POS interface of two routers are directly connected or connected through WDM, one side should be configured as master clock mode and the other side slave clock mode.
2. When POS interface of the router is connected with swiching device, if switching device is DCE, internal clock signal should be used; if POS interface is DTE, slave clock mode should be used.