Unable to share the Internet, the Source IP suddenly changed

Author: strategizing, source: IT expert network

Networking Mode

Recently, I applied for the installation of telecom internet broadband in my new house. In the first month, I went through the exclusive ADSL Broadband Network. Later I heard that several neighbors had to access the Internet, in addition, I want to save a little cost on the Internet, so I shared my application for ADSL bandwidth with them. Because the ADSL device presented by the local telecommunications department does not support the routing function when installing broadband, We have to purchase an eight-port switch, then, the common twisted pair wires are used to connect the ADSL device to the new switch device, and the computers with neighbors are all connected to the eight-port switch through the twisted pair cable.

To enable multiple users to access the Internet using the same dial-up account, I search for a Proxy server that allows multiple users to access the Internet at the same time. This is MS-Proxy, with this tool, we can easily share the Internet through the ADSL device. Since I know a little about the Internet, I agree that I use my computer as a LAN server, and all the other computers used by my neighbors as common clients, as long as I perform virtual dial-up Internet access in my computer system, the computers of other neighbors will be able to access the Internet using the ADSL device. In this networking environment, the author's computer and the neighbor's computer have been able to access the Internet normally, and the speed of access to the Internet is also very satisfactory.

Burst fault

When I came home from work at noon today, I met a neighbor who saw the author like a savior and grabbed the author's hand and said, "Dude, I found that my computer couldn't access the Internet when I was resting at home yesterday. Did you accidentally turn off the power of the switch ". I denied it on the spot because my wife had been surfing the internet at home yesterday. If the switch equipment in my home had a power failure, the computer in my home should not be able to access the Internet, I believe that the computer in the neighbor's house cannot access the Internet, which is definitely caused by the system itself, so I immediately went to the neighbor's house for on-site inspection and testing.

Activate the computer power of the neighbor's house, start the system, run the IE browser program after the system is started successfully, enter the URL of the Sina website in the address box of the browser, and click Enter, I found that the content of the website page could not be displayed normally. Then I tested several other website addresses and found that one website page could not be opened. Later I did not perform the QQ login test, obviously, the computer in the neighbor's house cannot access the Internet.

Is there a network virus in the faulty computer system, or the network cable connecting the computer to the switch device cannot be connected to the Internet? With this in mind, I first started the genuine Rising antivirus software installed in the faulty computer system to scan and kill the computer system, the author did not even find the shadow of a virus, which indicates that the network virus is not a "Sin!" problem ". After that, the author opened the computer system to run the text box, in which the input string command "cmd", click the Enter key, the system screen to switch to the MS-DOS work window, run the Ping command at the command line prompt in the window to test whether the IP address of the local computer system can be pinged. The test result shows that the IP address can be pinged normally, this means that the NIC device of the faulty workstation is working normally and the TCP/IP protocol is working normally, I Ping the ADSL device address in my home. The test result is also normal. This shows that the faulty workstation can Ping the IP address of the LAN gateway. In theory, if you can Ping the gateway address, you should be able to identify that the twisted pair cable connecting the faulty computer to the switch does not have a short circuit or break, however, I am still a little worried about the connectivity of this physical cable, because the network twisted pair cable is squeezed by external force or the crystal heads at both ends of the cable rust, it may cause network access failure, so I borrowed a professional cable tester from the Organization to test the connectivity of the cable connecting to the faulty computer. The result showed that there was no problem with the cable.

Because the neighbor's computer uses the proxy server in his home to transfer the Internet, I began to doubt whether the proxy server encountered any accidents. In order to verify whether my guess is correct, I specifically uninstalled the agent server software from my computer system and restarted the system, after that, I re-installed and set up the proxy server software in the correct way. However, the computer in the neighbor's house still cannot access the Internet normally. No way. I knocked on another neighbor's door and tested the Internet access in his computer system. As a result, I found that the computer system of his house could not access the Internet either, obviously, this fault is not caused by the LAN client.

Troubleshooting

Since multiple computers cannot access the Internet at the same time, will the switches connected to these computers not work properly? However, when I went online for a test in my own home, I found that access to the Internet is normal. If the switch is not working properly, my computer should not be able to access the Internet! In order to prevent problems with the switch port, I connected my computer to different switch ports for testing. The result shows that my computer can access the Internet normally no matter whether it is connected to any switch port.

So what makes the computer in the neighbor unable to share the author's ADSL device to access the Internet at the same time? I tried my best to recall in my mind that my nephew had used his computer yesterday, and I guess most of the problem lies in my computer. I immediately log on to my computer system and open the parameter configuration interface of the proxy server. The result shows that the IP address used for local network connection has changed to "192.168.1.1, this address is actually the connection port address of the local area network of the ADSL device.

Windows XP is installed in my computer system. By default, the system automatically searches for a LAN when it is started to see if a suitable IP address is available, this process will significantly reduce the startup speed of the computer system, so I specifically changed my computer ip address to "192.168.1.88", in order to increase the system startup speed, but now I see that the IP address of the computer has changed to "192.168.1.1". It seems that my nephew changed the IP address of the computer yesterday. As a result, I changed the local network connection IP address of my computer to "192.168.1.88". After setting the IP address, I restarted the computer system and made a virtual dial-up to access the Internet. Then, I went to the computer system of my neighbor's house for a test. The result showed that the failure to access the Internet had disappeared.

Fault Summary

Although various network faults often occur in the LAN, most of the faults are related to network settings. When solving the fault caused by network settings, many friends will simply think that the network fault is caused by the network equipment in the LAN, and has nothing to do with their own computers, in this way, it is easy to take some detours when solving network faults!