Be good at restarting network device to solve network problem

The working state of network equipment is directly related to the running state of network, after a long period of work, the network equipment working status is very easy to error, in fact, in the resolution of network equipment work caused by network failure, we should be good at "restart" network equipment, so that the network equipment working status quickly return to normal, This will solve seemingly odd network failures in the blink of an order. This article from the actual combat point of view, I hope the following content can bring you harvest!

Fault Playback

One employee of the unit said that the computer he used was not able to access the Internet, and that the unit's local area network was inaccessible. Originally thought that this is only the individual phenomenon, but who had thought that the unit of other colleagues on land continued to call, to the author reflects their computer can not normal access to the extranet and intranet.

I try to open my laptop, and access it to the LAN to try to access the Internet, to see if the LAN network is really unable to surf the internet, the results found that the author's notebook can be normal Internet, which indicates that the LAN is able to access the external network, and colleagues to the author of the Fault should be

So, the author uses a colleague's fault computer to log into the computer system as the administrator, and open the system's Start menu, and then execute the running command, from the pop-up System Run dialog box input string command "cmd", click the "OK" button, the System state switch to the MS-DOS window , at the command prompt of the window, enter the "Ipconfig/all" command, and after clicking Enter, the author discovers that the computer's network parameters are not faulty from the resulting interface that pops up later.

So what is the reason that the computer can not access the local area network, is it the TCP/IP protocol of the computer system is damaged, or installed in the computer network card device itself encountered a hardware failure? In order to verify the correctness of their analysis, the author executed the "ping 127.0.0.1" string command (shown in the following figure) in the running dialog box of the system.

The result returned by this command indicates that the network card device for the failed computer is properly installed and the TCP/IP protocol is not corrupted. In order to test whether the network card device can work correctly, the author also executes the "ping 192.168.10.11" string command in the system Run box (where 192.168.10.11 is the local IP address of the fault computer), the test indicates that the local NIC is also able to work correctly.

After excluding the network configuration factors of the local computer, the author also ping the IP address of the domain network gateway to detect whether the failed computer can normally access the LAN router, this time the ping command returned the test result is "Request timed out", Is this a problem with the routers in the LAN, or is there a faulty line connection between the local computer and the router? Considering that the author has successfully tried to use his own notebook computer LAN Internet access, so the router in the LAN should be normal, so the only possibility is that the computer to the router connection between the line has a problem.

Will it be that the physical circuit has a short circuit or fracture phenomenon, which leads to a colleague's computer can not be normal Internet? In order to test the normal connectivity of the physical circuit, the author immediately found a professional cable tester, the network cable connected to the computer connectivity test, the test results show that the physical circuit is no problem. Without a clue, the author began to suspect that a colleague's computer might be infected with a worm, because the virus sometimes leads to network failure.

Considering the killing virus is a very time-consuming thing, and now can not confirm that the virus is "to provoke" the curse, so the author decided to use their own notebook computer temporarily replace the fault of the computer access to the local area network. When I insert the network cable from my colleague's office into the internet port of my notebook computer, and try to ping the gateway address in the LAN, unexpectedly found that the author's notebook computer can not ping the gateway, which means that the computer can not be connected to the Internet is not the fault of the virus, but also with the configuration of the local computer is irrelevant , and when you open the status display interface for a local connection, when I see a network cable that is accessed through a colleague's office network, the computer can only send packet information externally and not receive information from the network.

Because the author's notebook computer is completely normal, and now even the notebook computer can not access the network cable, the reason for the problem is definitely out of the network connection, that will not be some network equipment in the LAN problem? The author came to the colleague's next door office, and tried to borrow the office network cable for the Internet test operation, the test results let the author feel very surprised, incredibly can the normal Internet, this is how to return? The same floor of all computers should be connected to the same switch, why some computers can surf the internet, some computers do not surf the internet, it is the switch part of the port there is a problem?

Here, I do not have any good Shifa can be used, had to come to the LAN room to open the junction cabinet, ready to see the switch port working status is normal. Open the wiring cabinet, the author carefully observed several two-layer switch in the signal state, found that all the lights are almost in green flashing state, this state looks normal. Since the eyes can not see the fault, the author had to use the notebook in turn to connect each of the two-layer switch for online testing.

When the notebook is connected to the first switch, the notebook can be normal access to the Internet, connected to the second switch, the notebook can also normal internet, it is connected to the third switch, the notebook can not normally access the network, is the third switch has a problem? The author is not at ease, in the connection state, and ping a LAN router address, the results found that the router can not ping; then, the author of the notebook computer into a third switch in another port, and continue to ping command test, But after testing all the ports can not ping the gateway address, and then carefully observe the third switch Control Panel in the signal state, the author unexpectedly found all the port signal is green, according to the reason that only the plug into the network cable port signal is green, Why is the empty port corresponding to the signal light is also green? It is clear that the third switch itself has failed in its working state!

After finding the cause of the failure, the author immediately disconnect the power of the third switch, after a period of time, and then reconnect the power to reboot the switch; when the switch starts to stabilize, the writer immediately tests the connectivity of the switch with a notebook computer, This time the author found that through the switch notebook computer has been able to ping through the gateway address, it seems that the third switch working status has returned to normal. As a result, the author rushed to the failure of the computer next to the Internet access operation, the results did not let the author again disappointed, the failure of the computer finally able to normal Internet; At the same time, other repair failures of several colleagues also said that network access has returned to normal. [More brilliant technical Articles-★ programming introduction ★ NET]

Fault Summary

Although the fault has been ruled out, but the author still has not figured out, that is why in the same floor of the computer some can surf the internet, and some do not? According to each floor of the computer is connected to the same switch network structure, should not appear this phenomenon ah, unless the switch port has a problem! Later, the author spent a certain amount of time combing the computer room wiring connection, the result found that the Internet can not be connected to the computers have been linked to another mobile switch, and the mobile switch after the problem, all the computers connected to this switch will naturally not be online, This is also the reason why some other colleagues repair the failure at the same time.

Once again, the author thinks that when checking the working status of the switch or other network equipment in the future, we can not simply observe whether the signal is in a green blinking state, because many network devices may have a system cache error after working for a long time. This makes it easy to have some false state information, and considering that network devices such as switches are generally not prone to damage, so when we suspect that their working status is in trouble, they often just need a reboot, which may easily solve a variety of strange network failures.

Of course, there is a need to remind the network administrator is that we must develop a strict management system for the computer room, firmly prohibit any user arbitrarily plug in the wiring cabinets in the network cable, effectively prevent users to plug and unplug the cable and affect the normal operation of the entire local area network.