With the deepening of educational informatization in China, the development of network construction in colleges and universities is becoming more and more perfect. After more than ten years of construction, the coverage of university campus network has expanded rapidly, the construction level has gradually improved, and the application scope has been expanding. Today's campus network has been closely linked with the work, study and life of teachers and students. The following are the commands and methods I have compiled to judge network faults. Welcome to refer to them!
1, the whole network is strangely impassable.
In the actual troubleshooting process, for some large networks, it is easy to have strange faults that the whole network is blocked. It's strange because all the phenomena look normal, the indicator lights and configuration have been checked, and there is no problem, but the network just doesn't work; What's even more amazing is that in the process of impassability, one or two computers can occasionally visit intermittently. In fact, this is a typical network storm phenomenon, which mostly occurs in some large and medium-sized networks. There are many viruses in the network, and then they infect each other. Because there are many computers in the network, the amount of data transmission is very large, which directly occupies the port, making normal data transmission impossible. The most direct way to solve this network storm caused by virus is to find out the source of the storm. At this time, you only need to install a firewall on a computer in the network, such as Kingsoft Netdart. After the firewall is enabled, you will find that the firewall keeps calling the police. You can use it at? Safe state? The security log of the tag shows that the firewall intercepted the virus attack from the same IP address. At this time, you only need to find out which computer it is according to the IP address, disconnect the network for virus killing, and generally solve the problem.
Tip: As a network administrator, even under normal circumstances, it is necessary to install a firewall like Kingsoft Netdart to find out the source of the virus flowing in the network and take preventive measures to avoid further expansion of the harm.
However, the best way to avoid network storm is to divide subnets and install online antivirus software. Divide subnets, so that there are fewer computers in each subnet, so that even if viruses spread to each other, the amount of data generated is not large, which will not endanger the whole network. Installing online antivirus software can keep the whole network running at a high speed and smoothly.
2. The network is blocked due to group policy.
This kind of fault mainly exists between Windows 2000/XP/2003 systems, because the group policy sets that access from the network is prohibited. So we can go in? Run? Enter through the window? Gpedit.msc？ And press enter, in the group policy window that opens, select? Local computer policy? Computer configuration? Windows settings? Security settings? Local strategy? User rights assignment? , and then double-click on the right? Deny access to this computer from the network? In the window that opens, select the account list and delete it.
3. The signal indicator is not on.
If the signal indicator does not light up, it means that there is no signal transmission, but it is certain that the line is normal. Then don't try to replace the network cable connected to the computer with another computer, or use the tester to check whether there is signal transmission. If there is signal transmission, it is a problem with the local network card. In practical work experience, it is a common fault to prove that the network card can not transmit information. In this regard, you can first check whether the network card is installed normally and whether the IP settings are wrong. You can try to Ping the IP address of this machine. If you can Ping the general rules, there is not much problem with the network card. If not, you can try to reinstall the network card driver to solve it. In addition, for some integrated network cards or low-quality network cards, it is easy to be unstable, that is, all settings are correct, but the network is not. In this regard, the method of disabling the network card and re-enabling it will also have unexpected effects.
4. Online neighbors are inaccessible.
The network is unblocked, and the connection with the Internet or local area network is normal, but other computers in the local area network cannot be accessed through online neighbors. There are many reasons for this failure, and the author can provide you with a simple solution here. Straight in? Run? According to the window? //Computer name (IP address)/Share name? To access shared folders on other computers in the network, this can not only bypass this fault, but also be faster than accessing through online neighbors.
5. The firewall makes the network impassable.
In order to ensure the security of the local area network, many friends have installed some firewalls. It is easy to cause some? Fake? Faults, such as Ping, can access the other party's computer, but QQ can be used without surfing the Internet. It is very simple to judge whether the fault is caused by the firewall. You just need to turn off the firewall temporarily, and then check whether the fault exists. The reason for this failure is also very simple. For example, when a user uses IE to access a website for the first time, the firewall will ask whether the program is allowed to access the network. Some users will continue to use this setting because they are not careful, which naturally leads to the network being blocked. A more radical solution is to remove this restriction in the firewall.
6. Slow down the use speed
Many network cards use 10M/ 100M adaptive network cards, although the default setting of network cards is? Adaptability? However, due to the speed of the switch or the manufacturing method of the network cable, some mismatches may occur. At this time, try setting the speed of the network card directly to 10M m by right clicking. Local connection? Open its properties window in. Ordinary? Tab, click? Configuration? Button to switch the opened NIC properties window to? Advanced? Tab，in？ Attribute? Select in the list? Link speed/duplex mode? On the right? Value? Select from the drop-down menu? 10 full mode? , click? Are you sure? Button to save the settings.
7. The connection indicator does not light up.
Note that there are two indicators on the RJ45 side on the back of the network card. They are connection status indicator and signal transmission indicator respectively. Under normal conditions, the connection status indicator is always green, and the signal indicator is red, which should be kept flashing. If we find the connection indicator, that is, the green light is not on, it means that the connection between the network card and the hub or switch is faulty. This can be eliminated by using a detector. If the switch and the network card are interconnected by multiple modules, dichotomy can be used for quick positioning. Generally speaking, this kind of fault is mostly caused by the weak connection of network cable and the use of inferior crystal head. Moreover, most of the fault points are problems connecting the two ends, such as the connector of the switch port and the network card connecting the computer. With the help of the tester, the fault can be easily found and solved.
8, configuration errors lead to network impassability.
The external manifestation of this fault is that the network indicator light is normal and can be Ping. Sometimes, you can access internal network resources, but you can't access external network resources. Sometimes you can only access websites through IP addresses, not through domain names. This is caused by typical improper network configuration, that is, the correct network card and DNS are not set. If the gateway is set incorrectly, you can only access this computer in the local area network. If DNS is set incorrectly, it cannot be resolved when visiting external websites. To do this, we just need to open the properties window of the local connection and open? Internet protocol (TCP/IP)? Properties window, and then set the correct default gateway and DNS server address.
Network impassability is a complex and changeable fault, but as long as we master its essence, understand the steps of network construction and are familiar with the prone points of faults, we can easily solve the problem of network impassability with constant changes.
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