Causes and solutions for slow speed of LAN

Faults in computer networks are inevitable. Network fault diagnosis is an important task in network management. Generally, when the network encounters a connectivity fault such as information failure and cannot browse the Web, the fault phenomenon is clear and easy to observe and locate the fault point. It is not difficult to solve such a fault. However, the biggest headache is that the network is accessible, but the network speed slows down.

When faced with such "soft" faults 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 handle actual problems.

1. network speed slows down due to network cable problems

We know that the twisted pair wires are tightly twisted together by four pairs according to strict regulations to reduce the effect of crosstalk and background noise. At the same time, in the T568A standard and the T568B standard, only four lines of twisted pair wires 1, 2, 3, and 6 are used. Among them, 1, 2 are used for sending, and 3, 6 are used for receiving, and 1 and 2 must come from a bypass pair, and 3 and 6 must come from a bypass pair. Only in this way can we avoid crosstalk to the maximum extent and ensure data transmission. In practice, I found that the network cable made according to the correct standard (T586A, T586B) has a great risk. The following figure shows that the network speed is slow at the beginning. The other is that the network speed is normal at the beginning, but after a period of time, the network speed slows down. The latter case is very obvious on a desktop computer, but the network speed is normal when you use a laptop to check. After years of practice, I have found that the slow speed caused by incorrect Network cables is also related to the quality of the network adapter. Generally, the NIC of a desktop computer is inferior to that of a laptop, using a laptop to check that the network speed is normal does not eliminate the problem that the network cable is not created in accordance with the standard. We now require that all network cables be squashed according to T586A and T586B standards. During fault detection, we cannot use laptops instead of desktop computers.

2. slow network speed due to loop in the Network

This phenomenon rarely occurs when the number of nodes involved in the network is not large and the structure is not complex. However, in some complex networks, there are often redundant backup lines. A loop may be formed when a connection is accidentally established. For example, the network cable is connected from the network center to the computer room, and then from the computer room to the computer room. At the same time, a backup line is directly connected from the network center to the second room of the computer. If these lines are connected at the same time, a loop is formed, and data packets are continuously sent and verified, thus affecting the overall network speed. It is difficult to search for this situation. In order to avoid this situation, we must develop a good habit when laying the network cable: The network cable is marked with an obvious label, where there is a backup line should be well documented. When such a fault is suspected, the partitioning and segmentation method is generally used.

Iii. Broadcast storms caused by hardware faults on network devices, resulting in slow network speeds

As the main means to discover unknown devices, broadcast plays a very important role in the network. However, as the number of computers in the network increases, the number of broadcast packets increases dramatically. When the number of broadcast packets reaches 30%, the network transmission efficiency will be significantly reduced. When the network adapter or network device is damaged, it will send broadcast packets continuously, resulting in broadcast storms and network communication paralysis. Therefore, when the hardware of the network device fails, the network speed may also slow down. If such a fault is suspected, replace the hub or switch with the replacement method to eliminate the fault of the collector line equipment. If these devices are not faulty, after the power of the hub or switch is turned off, run the "Ping" command in DOS to test the involved Computers one by one and find the computers with the faulty Nic, the network speed can be restored after a new Nic is changed. NICs, hubs, and switches are the most vulnerable devices to slow network speeds.

4. A port in the network forms a bottleneck, leading to slow speed.

In fact, the WAN port and LAN port of the router, the switch port, the hub port, and the server Nic may all become network bottlenecks. When the network speed slows down, we can use the network management software to view the data traffic of routers, switches, and server ports during peak hours. We can also use the Netstat command to count the data traffic of each port. Based on this, identify the network data flow bottleneck and try to increase its bandwidth. There are many specific methods, such as replacing the server NIC with 1000 M or M, installing multiple NICs, dividing multiple VLANs, and changing the vro configuration to increase bandwidth, which can effectively alleviate network bottlenecks, it can increase the data transmission speed to the maximum extent.

5. slow network speed caused by the influence of worms

The effect of E-mail virus on network speed is becoming more and more serious, which is harmful. This virus causes infected users to send emails continuously as soon as they access the internet. The virus selects random documents in the user's personal computer to be appended to the random address of the user's address book for mail sending. Hundreds of such spam emails are sent out in batch, and some are returned in batches to pile up on servers. This causes significant internet congestion on some backbone networks, significantly slowing down the network speed, and paralyzing the LAN. Therefore, we must promptly upgrade the anti-virus software used. Computers must also promptly upgrade and install system patches, uninstall unnecessary services, and disable unnecessary ports, to improve the security and reliability of the system.