Reasons for communication interruptions between a device and DCN after a WDM hub is connected to a DCN

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Question:
The communication between a BWS 1600G device and DCN is interrupted after the hub of the BWS 1600G device is connected to the DCN using two network cables.
The BWS 1600G device uses three subracks, and the ETH indicator on the system control board is steady on.
After a computer is connected to the hub, the computer crashes, causing an NE login failure.
Analysis:
Other ports on the switches in the DCN work properly. Disconnect the network cable from the faulty NE, and then connect the network cable to a normal port. The issue is replicated, the fault is not caused by the switches.
Set the IP address of the computer to the same as that of the device. Test the two network cables connected to the hub respectively. No abnormality occurs, indicating that the fault is not caused by the network cables and IP address configuration.
Check and find that the hub is connected to the DCN using two network cables. This indicates that a loop is formed in the DCN. In this case, the computer is connected to the hub using a network cable, and the CPU usage reaches 99%. As a result, the computer crashes, the indicator of the network interface card (NIC) is steady on, and the ETH indicator of the system control board on the WDM device is also steady on. This indicates that the DCN receives a large volume of data send by itself. As a result, the communication between the NE and DCN is interrupted. Remove one network cable between the hub and DCN. The computer works normally again. In addition, reset the system control board, and then the NE can be logged in to normally.
Root cause:
The main reasons for DCN network interruptions are as follows:
1. Issues of switches in the DCNs
2. Issues of network cables
3. Issues of IP configurations
4. Issues of the hub
Answer:
Remove one network cable between the hub and DCN, and then reset the system control board.
Suggestion and conclusion:
None

Other related questions:
Interruption of the communication between WDM devices and the DCN network after the WDM devices are connected to the DCN network through hub
The main reasons for the interruption between WDM devices and the DCN network are as follows: 1. Switch issues in the DCN network 2. Network cable issues 3. IP address configuration issues 4. Hub issues

Whether there are risks when the DCN gateway of an OSN 9800 is switched
When the DCN gateway is switched, the network is normal and services will not be interrupted. However, the NE monitoring function may be affected.

Whether there are risks when the DCN gateway of OptiX OSN 9800 is switched
When the DCN gateway is switched, the network is normal and services will not be interrupted. However, the NE monitoring function may be affected.

Available DCN solutions and application differences of these solutions
A data communication network (DCN) provides communication channels for NEs that are managed uniformly to achieve remote management and maintenance on the NEs. DCN solutions are classified into inband DCN and outband DCN. The inband DCN uses service channels provided by managed devices to achieve device management. The outband DCN provides dedicated communication channels to achieve device management for NEs that are uniformly managed. Huawei provides the following outband DCN solutions: HWECC solution: When a network is composed of only transmission devices, the HWECC solution is the first choice. IP over DCC solution: When a network is composed of both Huawei transmission devices and third-party devices that support the TCP/IP function, this solution is the first choice. The solution also applies when the network is composed of only Huawei transmission devices. OSI over DCC solution: When a network is composed of both Huawei transmission devices and third-party devices that support the OSI over DCC function, this solution is the first choice.

Precautions for DCN subnet division
Take the following precautions during DCN subnet division: Ensure that the number of NEs in a DCN subnet is within the recommended range. Disable the DCC and GCC channels between DCN subnets. Before dividing a DCN into subnets, plan an external DCN for connecting to gateway NEs in each subnet. Ensure that DCN subnet division must not compromise the existing DCN route restoration (protection) capability. Group separated optical and electrical NEs at the same site in the same DCN subnet.

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