A wireless network is the main cause of network failure.

A loop problem occurs in the use of wireless networks. Where is the problem? Who is the culprit? The author of this article gives you a detailed description of how to set up your own experience.

Unit A subnet has been working normally, but I found that workstations in subnet A recently cannot access the LAN server. After some careful checks, I can see that the new switch devices in subnet A are often unable to connect to the core switches in the LAN.

Considering that workstations in other subnets in the LAN can work normally, I believe that the core switch equipment in the LAN does not have any problems, however, the newly used switch in subnet A is A device that has just been unmounted, so the possibility of failure of the device is not very high, so I think it is very likely that the connection between the newly invested switch device in subnet A and the core switch of the local area network fails. After careful on-site investigation, I found that the new switch in subnet A is directly connected to the core switch of the LAN Using multimode optical fiber, the possibility of A connection failure occurs when you use this media to connect to the network. Therefore, I first thought about whether the new switch in subnet A will have A "soft" fault, I restarted the new switch device. After the device was restarted and stabilized, I tried to access the server on the LAN from subnet A. The result showed that the Network was still faulty. I was unwilling to restart the core switch of the Local Area Network. During the start of the core switch, I carefully observed the Signal status in the control panel of the switch, the result shows that the signal light corresponding to the port connecting to the new vswitch of subnet A blinks for A few seconds and then disconnects immediately. Is there any bad contact between the network connection lines?

As a last resort, I have to turn my skeptical eyes to the physical connection media. Because the connection media used here is an optical fiber cable, for this reason, the author conducts one-by-one investigation and tests on factors such as the Optical Fiber adapter, the fusion joint at both ends of the optical fiber, the trunk cable of the optical fiber, and the optical fiber jumper through troubleshooting methods. No suspicious phenomena were found, during the above troubleshooting and testing, we occasionally saw that the new vswitch of A sub-network can be connected to the core vswitch of the LAN, but it was immediately disconnected several seconds later.

Is it possible that the new switch in subnet A does not properly set the working parameters? Taking this into consideration, I immediately press the "Recover" button in the control panel of the new switch in subnet A to restore all parameters of the device to the default factory value, then, the network parameters are reset according to the correct method, and the new switch device in subnet A is restarted after the save operation is performed. I thought that the network failure could be automatically eliminated after the new switch was restarted and stabilized. However, when I tried to access the LAN server from A workstation in subnet A again, I found that subnet A still cannot normally access the LAN server.

In desperation, I accidentally saw A fiber jumper on the new switch in subnet A as if there was A problem, so I pulled the jumper down, at the same time, I carefully observed the working status of the signal in the control panel of the new switch, and found that the working status of the port that is directly connected to the local area network core switch has returned to normal, in this case, when you try to access the server on the LAN from subnet A, the network access is normal. To verify that the failure of A subnet workstation to access the LAN server is caused by this jumper, I re-connect it to the new switch in subnet, the result shows that as long as the patch cord is connected, the Link port signal in the control panel of the new switch is in a flash. After a few seconds, the corresponding port signal will automatically go out, at this time, we will find that the subnet workstation will not be able to access the LAN server.

According to the above network failure phenomenon, the author does not hesitate to think that this jumper is a crime of network failure, so I began to carefully check this jumper and the network equipment connected by the jumper. As a result, I can see that this optical jumper is connected to the Gigabit module of another switch. When I look at another switch, I can see that two Wireless AP devices are connected to the switch device at the same time, after removing any of the two Wireless AP devices, the workstation in subnet A can immediately access the LAN server. Obviously, the real cause of network failure is the two Wireless AP devices.

After further investigation, I have seen that the modes of the two Wireless AP devices should be set to the Access Point working mode according to the principle, but I don't know what's going on, I found that the working mode of one Wireless AP device has been changed to the working mode of Access Point Client. In that case, two Wireless AP devices directly connected to the same vswitch device form A wireless bridging network, which leads to A network loop in subnet, this network loop makes the workstation in subnet A unable to access the LAN server.

TIPS:

Through the above network faults, it is not difficult to find out how important network wiring is. On the surface, network cabling seems very simple. In fact, it is advanced, practical, confidential, secure, and reliable. It belongs to a system engineering. Only by having a full understanding of network cabling can we pay enough attention to it, and be willing to invest money in the actual cabling process to make the network cabling more systematic, standardized, and reasonable. Only by systematically wiring the network can the flexible scalability and smooth upgrade of the communication network be ensured, and the network maintenance workload can be greatly reduced in the future, in particular, it can greatly reduce the cost of continuous investment in network maintenance. Network Cabling is actually a network platform with good transmission performance for the entire communication network system, ensure that the entire communication network system is mature, flexible, open, universal, and secure. At the same time, there is a very good performance-price ratio. For example, when wiring the entire floor or the entire building, as long as the staff resources are reasonably planned and configured, the maintenance cost of network communication can be reduced to half of the original cost.

You can use a shared standard edge system to conveniently and quickly deploy, install, detect, and debug network devices, in this way, the Network Unit's investment in network construction can achieve an ideal return on efficiency. Through systematic and structured network cabling, the communication network can be made up of a star physical structure with diversified functions. This structure is almost applicable to various topology structural requirements, this ensures the wide applicability of the established network. Because of this network structure, it is especially convenient for maintenance and expansion and upgrade. You only need to make some local changes at some network nodes, and there is almost no need to move any cables or equipment.

In addition, the planning and cabling should be conducted in accordance with the principles of advancement and practicality. Various technologies involved in network cabling should adopt open technical standards, to ensure convenient interconnection and expansion of network systems; of course, to ensure good scalability in the future, we should also adopt standardized design in the Cabling Process, and select standardized network equipment and products; to ensure the maintainability of the network, we should adopt modular design principles whenever possible during network cabling planning, fully consider the hierarchical and visualized network maintenance, and ensure that the network maintenance is simple and easy.