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Knowledge Base

At an office, all the boards on the master subrack report the COMMUN_FAIL alarm because a network cable is wrongly connected to the COM interface

Publication Date:  2012-07-25  |   Views:  121  |   Downloads:  0  |   Author:  SU1001787622  |   Document ID:  EKB0000342863


Issue Description

 A new OptiX OSN 6800 NE of V100R003 contains two subracks: a master subrack and a slave subrack. After the NE is powered on, all the boards on the master subrack report the COMMUN_FAIL alarm with 0x03. On the T2000, the boards appear dimmed and cannot be managed. The boards on the slave subrack work properly.
The software version information is as follows:
1.NE version:
2.T2000 version: V200R006 

Alarm Information

COMMUN_FAIL with 0x03

Handling Process

 1. Set the DIP switches of the AUX on the slave subrack to 0. Move the AUX to the master subrack. Restart the master subrack. The fault persists.
2. Move the AUX on the master subrack to the slave subrack. Restart the slave subrack. The slave subrack does not report the COMMUN_FAIL alarm. Therefore, the problem lies outside the AUX.
3. The fault persists after the master subrack is restarted. In addition, the boards cannot be managed. Therefore, the alarm is true.
4. Interchange the SCC on the master subrack and the SCC on the slave subrack. Reconfigure the logical slots. The fault persists. Therefore, the problem lies outside the SCC.
5. Engineers doubt that the problem lies in a cascade interface on the EFI or AUX. Check the cascade interfaces on the EFI and AUX. It is found that a network cable is connected to the COM interface on the EFI of the master subrack. The COM interface is for commissioning. No network cable can be connected to the interface during deployment. Check the other end of the network cable. It is found that the network cable is connected to the alarm cascade interface, ALMO2, on the slave subrack at the other end.
6. The field supervisor confirms that the network cable is installed on the site. Move the network cable from the COM interface to the ALMO1 interface on the master subrack. The COMMUN_FAIL alarm disappears. The fault is rectified.
7. In conclusion, the cause of the fault is as follows:
On the master subrack, the COM interface on the EFI is not isolated from the AUX. In other words, all the data received on the COM interface is broadcast to all the Ethernet interfaces on the subrack. The wrong communication between the COM interface on the master subrack and the ALMO2 interface on the slave subrack causes a broadcast storm to the ETH VLAN. As a result, the ETH communication on the master subrack is affected. 

Root Cause

 1. The alarm parameter 0x03 indicates that the Ethernet communication is interrupted. According to experience, the problem may lie in the AUX. The board communication on the OptiX OSN 6800 is similar to that on the OptiX OSN 3500.
2. The SCC fails.
3. The alarm is false. To handle such a problem, restart the subrack.
4. A cascade network cable between the subracks is connected to a wrong network interface.
5. All the boards fail. Such a problem seldom occurs.
6. The EFI fails. Such a problem seldom occurs. 


 Strictly abide by the Fiber and Cable Installation Guide and Data Configuration Guide during deployment.