Symptom
In a network shown in the following figure, the port working modes on the LOG boards and the interconnected routers are both set to 1000M Full-Duplex. In this case, when the fiber at the transmit end of the LOG board on NE 1 is broken, an active/standby switching is normally performed on router A but fails on router B. As a result, services are interrupted and the system reports the R_LOS alarms. The routers on the client side report the LPT_RFI alarms.
Cause analysis
l The port working modes on the LOG boards and the routers are 1000M Full-Duplex. After the fiber at the transmit end of the LOG board (LOG A) on NE1 is broken, router A detects the LINK_FAIL and switches to the standby router. Because the port working mode is 1000M Full-Duplex, router A continues emitting light. LOG A fails to detect the LINK_FAIL and cannot trigger the LPT function. As a result, router B cannot trigger an active/standby switching.
l Set Auto-Negotiation to Enabled for the LOG boards and set the port working modes on the routers to Auto-Negotiation. After the fiber at the transmit end of LOG A on NE1 is broken, router A detects the LINK_FAIL and switches to the standby router. Then LOG A detects the LINK_ERR and triggers the LPT function. In this case, LOG B shuts down the local connection. As a result, router B detects the LINK_FAIL and triggers an active/standby switching. That is, services are normal.
Procedure
1. Set Auto-Negotiation to Enabled for the LOG boards.
2. Set the port working modes on the routers to Auto-Negotiation.
Result
The problem is resolved.
