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In this post, I want to share a case about the OSN 1800 is Unreachable to the NMS issue. I hope it can help you in dealing with similar problems.

Problem Description

An OSN 1800 NE at a site in country M is unreachable. After the SCC board of the subrack is replaced, the problem persists. After the replaced SCC board is inserted into a new OSN 1800 subrack, the new subrack is reachable.

Possible Cause Analysis

The OSN 1800 NE has been configured as a slave subrack (the master/slave subrack configuration is supported only in V100R002 and later versions). This can be observed by checking its ID settings. The subrack is unreachable when an attempt is made to reconfigure it as a master subrack or to log in to it directly through a PC.

Fault Isolation Procedure

Step 1 Confirm that the OSN 1800 subrack has been configured as a slave subrack. Based on this information, Huawei determines that the ID of the subrack may cause this problem.

Step 2 Set the DIP switches on the SCC board to 1001 in binary to restore the default subrack mode (independent subrack mode). Specifically, toggle the 1st and 4th switches to ON and the 2nd and 3rd switches to OFF, as shown in the following figure. After that, insert the SCC board back to the OSN 1800 subrack.

Step 3 Observe the STAT indicator on the SCC board. When the fan rotation speed slows down, the STAT indicator on the SCC board blinks slowly, indicating that the SCC board has booted and the subrack is restored to work in independent mode. Remove the SCC board and toggle all the DIP switches to OFF (that is, set the DIP switches to 0000 in binary) and then insert it back to the subrack. Allow some time for the SCC board to reboot.

After the SCC board reboots, the problem is resolved. The OSN 1800 subrack can be logged in.

Related Concept

• The OSN 1800 subrack can work in either independent subrack mode or master/slave subrack mode. You can determine which subrack mode is in use by checking the subrack ID on the U2000. In independent subrack mode, the subrack ID is 255. It cannot have any slave subrack or function as a slave subrack. In master/slave subrack mode, the subrack ID is within the range of 0–6. Currently, an OSN 1800 master subrack supports at most six slave subracks. The subrack ID 0 means the master subrack and subrack IDs 1–6 means slave subracks.
• For NG WDM equipment, subrack IDs are set using the DIP switches. However, for OSN 1800 equipment, the subrack IDs have to be set using the U2000. The following figure shows the U2000 GUI in which the OSN 1800 subrack IDs are set.

• The default ID of an OSN 1800 subrack is 255. That is, the subrack is in independent mode by default.
• After a subrack is configured as a slave subrack (by setting the subrack ID to a value within the range of 1–6), the SCC board on this subrack can communicate with only the master subrack. If the subrack is not connected to the master subrack, then the subrack will be unreachable.

Conclusion and Suggestion

When such a problem occurs, there is no need to replace the SCC board in the subrack. Instead, set the DIP switches to binary value 1001 to restore the default subrack ID, as described in the Fault Isolation Procedure. Note that this method applies only to the OSN 1800 1U and 2U subracks of the global version.