Computer network failure is inevitable. After the campus network is built and running, network fault diagnosis is an important task of network management. Generally, when there are connectivity failures such as information inaccessibility and inability to browse the web, the failure phenomenon is relatively clear, and it is easy to observe and locate the failure point. It is not difficult to resolve such failures. However, the most troublesome thing is that the network is connected, but the network speed becomes slow. When faced with this kind of "soft" failure for the first time, some people are often helpless. This article introduces the common causes and troubleshooting methods for such "soft" faults to improve your ability to deal with actual problems.
First, the network cable problem causes the network speed to slow down
We know that the twisted pair is tightly twisted together by four pairs of wires according to strict regulations to reduce the impact of crosstalk and background noise. At the same time, in the T568A standard and T568B standard, only four wires 1, 2, and 3, 6 of the twisted pair are used, of which 1, 2 are used for transmission, 3, 6 are used for reception, and 1, 2 must come from a Yes, 3 and 6 must come from a winding pair. Only in this way can we avoid crosstalk to the greatest extent and ensure data transmission. In practice, I found that the network cables not made according to the correct standards (T586A, T586B) have great hidden dangers. The performance is as follows: one situation is that the network speed is very slow at the beginning of use; the other situation is that the network speed is normal at the beginning, but after a period of time, the network speed becomes slow. The latter case is very obvious on a desktop computer, but the network speed is normal when checked with a laptop. For this problem, I have found through many years of practice that the slow speed of the network caused by the network cable not made according to the correct standard is also related to the quality of the network card. The performance of the network card of a general desktop computer is not as good as that of a laptop computer. Therefore, when troubleshooting with the exchange method, using a laptop computer to detect the normal network speed does not rule out the problem that the network cable is not made according to the standard. We now require that all cables be suppressed according to the T586A and T586B standards, and laptop computers cannot be used to replace desktop computers when detecting failures.
Second, there is a loop in the network causing the network speed to become slow
This phenomenon generally seldom occurs when the number of nodes involved in the network is not many and the structure is not very complicated. However, in some more complex networks, there are often redundant backup lines, which will form a loop if they are accidentally connected. For example, the network cable is connected from the network center to the first computer room, and then from the first computer room to the second computer room. At the same time, there is a spare line from the network center directly connected to the second room of the computer. If these lines are connected at the same time, it will form a loop, and the data packets will continue to send and verify data, which affects the overall network speed. This situation is more difficult to find. To prevent this from happening, it is required that we must develop good habits when laying the network cable: the network cable is marked with obvious labels, and records should be made where there are spare lines. When it is suspected that such a fault occurs, the method of gradual elimination by partitioning is generally adopted.
Third, the broadcast storm caused by the hardware failure of the network equipment caused the network speed to slow down
As the main means of discovering unknown devices, broadcasting plays a very important role in the network. However, as the number of computers on the network increases, the number of broadcast packets will increase dramatically. When the number of broadcast packets reaches 30%, the transmission efficiency of the network will decrease significantly. When the network card or network equipment is damaged, it will continuously send broadcast packets, resulting in a broadcast storm and paralyzing network communication. Therefore, when the hardware of the network device is faulty, it will also cause the network speed to slow down. When such a fault is suspected, the hub or switch can be replaced by a replacement method to eliminate the fault of the hub device. If these devices are not faulty, after turning off the power of the hub or switch, use the "Ping" command under DOS to test the involved computers one by one, find the computer with the faulty network card, and replace the new network card to restore the normal network speed. Network cards, hubs, and switches are the most prone to failures and cause slower network speeds.
Four, a port in the network has formed a bottleneck, resulting in a slower network speed
In fact, router WAN ports and LAN ports, switch ports, hub ports, and server network cards may all become network bottlenecks. When the network speed is slow, we can use the network management software to view the data traffic of routers, switches, and server ports during the peak hours of network usage; we can also use the Netstat command to count the data traffic of each port. Accordingly, confirm the location of the bottleneck of network data circulation, and try to increase its bandwidth. There are many specific methods, such as replacing the server network card to 100M or 1000M, installing multiple network cards, dividing multiple VLANs, and changing the router configuration to increase the bandwidth, etc., which can effectively alleviate the network bottleneck and maximize the data transmission speed.
V. The influence of worms causes the speed of the Internet to slow down
The worms distributed via E-mail have a more and more serious impact on the network speed and are extremely harmful. This virus causes infected users to send out emails as long as they are online. The virus selects a random file in the user's personal computer to attach it to a random address in the user's machine's address book to send the mail. Hundreds and thousands of such spam emails are lined up and sent out, and some are returned in batches and piled up on the server. It caused obvious congestion on some backbone Internets and slowed down the network speed, which caused the LAN to be paralyzed. Therefore, we must upgrade the anti-virus software used in a timely manner; the computer should also be upgraded in a timely manner, install system patches, and uninstall unnecessary services and close unnecessary ports to improve the safety and reliability of the system.
In short, the application of computer networks is becoming more and more extensive. It is very important to improve the management level of campus networks, keep learning, and pay close attention to theoretical knowledge and practical operation.
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