Cause analysis and solution of slow speed of local area network

Slow network is often encountered problems, for ADSL dedicated network users alone, the network speed of the situation is less slow. But for users of LAN access to the Internet, they often appear, such as Internet cafes, companies and schools and other places. A lot of user response, LAN after running for some time, found that the entire network speed suddenly slowed: Running company information System software and access to the company's local area network home page speed significantly reduced, access to the network speed is not as good as before.

When the network slows down, it is necessary to diagnose the network effectively, causing a lot of reasons for the LAN to slow down, the network cable, the connectors, hubs, network cards, drivers and so on hardware devices may cause the enterprise LAN speed slowed down.

In this case, first we need to check if the network cable is off, there is no impairment fracture, cable connectors are loose, bad contact, the router's power is loose or whether the interface is covered with dust or debris, resulting in congestion; and whether the network card is working properly, the IP address settings are not the same as other computer settings conflict and so on.

Topological structure of the network

Network topology unreasonable also can affect the speed. It includes the network cable erection is too long, networks redundant circuit.

First, check the physical distance between the two network devices. Now enterprises, Internet cafes and other local area networks are mostly used in five types of twisted pair, while the effective distance of five types of lines is 120~150 meters, the best distance is less than 80 meters. If the physical distance between two network devices exceeds 120 meters and there is no network relay device between them, the network transmission between them is slow. As for fiber optics, there is no such problem.

At this time we need to change the network topology, shorten the physical distance between two network devices or increase network relay devices such as hubs, repeaters, but also can be replaced by five-type or optical fiber.

Then count the number of repeaters passed between any two network devices. In 10Mbps Ethernet should not exceed 4, in 100Mbps Fast Ethernet should not exceed 2.

Loop problems affect the speed of the network, generally when the network is less involved in the number of nodes, the structure is not very complex, this phenomenon rarely occurs. But in some more complex networks, because some reasons often have redundant lines, it will constitute a circuit, the packet will continue to send and verify data, thus affecting the overall speed, and find more difficult. In order to avoid this situation, we must be in the laying of the network of good habits, network cable marked on the label, there is a standby line of the place to do a good record.

Broadcast storms affect network speed

Broadcast storm, which affects the speed of network, plays an important role in the network as the main means of discovering unknown equipment. However, as the number of network computers increases, the number of broadcast packets will increase dramatically. When the number of broadcast packets reaches 30%, the efficiency of network transmission will decrease obviously. When the NIC or network device is damaged, the broadcast packet will be sent continuously, causing the broadcast storm and paralyzing the network communication.

Therefore, when the network equipment hardware failure will also cause slow speed. When you suspect such a failure, you can first replace a hub or switch with a replacement to troubleshoot a hub device failure. Then turn off the hub or switch power after the ping command to the computer involved in one test, to find a computer with a faulty network card, replace the new network card can restore normal speed.

Port bottleneck blocking network transmission

In fact, the router's WAN port and LAN port, switch port, hub port, and server network card are all likely to become network bottlenecks. We can use Network management software to view routers, switches, server port data traffic (using the netstat command can also count the data flow of each port), confirm the location of network data circulation bottleneck, try to increase its bandwidth. such as replacing the server network card for 100M or 1000M, installing multiple network cards, by changing the configuration on the router to increase bandwidth and other methods can effectively alleviate network bottlenecks, to maximize the speed of data transmission.

Virus causes LAN speed down

Now many computer viruses such as Nimda, cover letter viruses and their variants, and so many of the network virus will cause a decrease in internet speed. If a computer gets infected with the virus, it spreads to other computers via the LAN or the Internet. The entire network is flooded with virus files blocking the network, increasing the load on the server or client computers. These factors will lead to a reduction in internet speed.

For example, a first-ever-popular cover letter virus. Users who preview virus letters and do not need to perform any attachments are already infected. Once the user is poisoned, the virus will send a large number of mail to the Address Book recipient, resulting in increased server and client load, the network caused congestion. Normal data frames cannot be transmitted, or even the entire network is paralyzed.

In order to prevent the virus interference, the network maintenance personnel need to check the poisonous anti-virus regularly, sets up the network firewall, modifies each kind of loophole. When a computer is poisoned, disconnect it from the network to prevent it from infecting other computers.