Reason why the computer cannot access the network

Blog 1:

I. Network Settings

This is because you need to manually specify the IP address, gateway, and DNS server connection mode, and use the proxy server to access the Internet. Carefully check the computer's network settings.
Ii. DNS server problems
When ie cannot browse the Web page, try the IP address first. If yes, it should be a DNS problem, the DNS problem may be caused by an error in obtaining the DNS when the network is connected or a problem with the DNS server itself. In this case, you can manually specify the DNS Service (the address can be the DNS server address provided by your local ISP, you can also use the DNS server address in other places .) In the network properties, (Control Panel-network and dial-up connections-local connection-right-click Properties-TCP/IP protocol-properties-use the following DNS server address ). Different ISPs have different DNS addresses. Sometimes it is a problem with the vro or Nic and cannot be connected to the DNS Service of the ISP. In this case, you can turn the vro off for a while or reset the vro.
Another possibility is that the local DNS cache is faulty. To speed up Website access, the system automatically saves a website that has been accessed and obtained an IP address to the local DNS Cache. Once the website is accessed again, then, the IP address of the website is not directly retrieved from the local DNS Cache through the DNS server for access. Therefore, if a problem occurs in the local DNS cache, the website cannot be accessed. You can execute ipconfig/flushdns in "run" to recreate the local DNS cache.
Iii. Problems with IE browser
When the IE Browser fails, browsing is naturally affected, or the IE is maliciously modified or damaged, leading to the inability to browse the Web page. At this time, you can try to use "Huangshan ierepair expert" to fix the problem (it is recommended to fix it in safe mode), or re-run IE (for example, if you encounter a problem that cannot be re-installed, refer: appendix 1 solves the problem of re-installing ie)
Iv. Network Firewall Problems
If the network firewall is improperly set, for example, the security level is too high, ie is accidentally put into the blocked access list, or the firewall policy is incorrect, you can try to check the policy, reduce the firewall security level, or directly turn it off and try to restore the normal state.
V. network protocol and NIC Driver Problems
IE cannot be browsed. It may be caused by network protocol (especially TCP/IP Protocol) or network card driver damage. You can try to re-drive the network card and network protocol.
Vi. Hosts file Problems
The modification of the hosts file also causes abnormal browsing. The solution is to clear the content in the hosts file.
VII. System File Problems
When the system files related to IE are replaced or damaged, the normal use of IE will be affected. You can use the SFC command to fix this problem. The Win98 system can execute SFC in "running, then run the scan. For Win2000/XP/2003, run SFC/scannow in "run" to try to fix the problem.
When only ie cannot browse the Web page while QQ can access it, it is often caused by Winsock. DLL, wsock32.dll, or wsock. vxD (VxD only exists in the Win9x system) and other files are damaged or lost. Winsock is an important part of the TCP/IP protocol. Generally, the TCP/IP protocol must be reinstalled. However, XP began to integrate the TCP/IP protocol, so it cannot be simply uninstalled and reinstalled like 98. You can use the netsh command to reset the TCP/IP protocol, restore it to the status when the operating system is installed for the first time. The procedure is as follows:
Click "start running", enter the "cmd" command in the running dialog box, and then enter "netsh int IP reset C: \ resetlog.txtlogs: The resetlog.txt file is used to record the command execution result. This parameter must be specified. The complete path of the specified log file is "C: \ resetlog.txt ". The result of executing this command is the same as deleting and re-installing the TCP/IP protocol.
Tip: The netsh command is a command line-based scripting tool. You can use this command to configure and monitor Windows systems. In addition, it provides an interactive network shell program interface, for the format of the netsh command, see the Help File (enter "netsh /?" ).
The second solution is to fix the above files. Win9x uses SFC to re-extract the above files. Win2000/XP/2003 uses the SFC/scannow command to fix the files. When SFC/scannow cannot be used to fix the files, you can try winsockfix, a repair tool released on the Internet, to search and download it online.
VIII. Real-time Monitoring of anti-virus software
This is not often seen, but sometimes it is related to real-time monitoring, because the real-time monitoring of anti-virus software is now added to the monitoring of web content. For example, kv2005 will cause IE to fail to browse the Web page on some machines (many friends have met it). The specific performance of kv2005 is as long as web page monitoring is enabled, after the Internet connection is started for about 20 minutes, ie will be unable to browse the Web page. If kv2005's web page monitoring is turned off, everything will return to normal. After a thorough reinstallation of kv2005, it will not be able to solve the problem. Although this problem does not occur for every sub-machine that installs kv2005, after all, the sub-systems of each machine are different and the installed programs are different. If IE cannot browse the webpage, check anti-virus software.
IX. Application Management Service Problems
When the web page cannot be opened only on QQ, You can restart it. However, even if it is restarted, after opening 7 to 8 web pages, you can only go to QQ. Sometimes, China Telecom often allows you to disable the application management service. The specific cause is unknown.
10. Virus Infection
This often occurs when you open ie. In the lower-left dialog box of the IE interface, the system prompts that the webpage is being opened, but the webpage does not respond for a long time. Check the process in the Task Manager (enter the method, place the mouse on the taskbar, right-click the Task Manager-process) to see how the CPU usage is. If it is 100%, you can be sure, if you want to run other programs, the virus is infected. Check which process occupies CPU resources greedily. after finding it, you 'd better record the name and click "end". If it cannot be completed, you need to start to secure mode to delete the stuff and enter the Registry. (method: start-run, enter Regedit) in the Registry dialog box, click Edit-search, enter the program name, find it, right-click to delete it, And then perform several searches, it can often be completely deleted.

There are a lot of viruses. When anti-virus software is powerless, the only way is to manually delete them.

Blog 2:

Generally, in a LAN, the following possibilities cannot be obtained:
1. the IE browser has been maliciously modified.
2. IP address conflict.
3. The network cable interface is loose.
4. system problems.
The above situations are my experiences in network management, and 80% of the four possibilities are maliciously modified by IE. 10% is an address conflict. 5% indicates that the network cable interface is loose. 5% is a system problem.

Check whether the network card can be pinged by pinging 127.0.0.1. Then, use ipconfig to check whether the configured address is the same as the displayed address. If the IP address is the same, it indicates no problem.

It's not a vswitch problem, it's not a network cable problem, it's just a Network Card problem .. Nic problems. You have to open the host and check whether the NIC is plugged in. If it doesn't work after the plug-in, simply buy another one .. If the NIC is external, directly find someone to repair ....

When the network connection is normal, it still cannot be connected to the network. Why ?"

It should be a system problem! Check the network connection! IP, DNS, and routing problems!
Maybe it may be your IE problem. Try again. No, it's still because your network is faulty. Check again.

It seems like a line problem, the telephone line is advanced separator, and then distributed to the cat and the server. If this step is correct, Skip, whether the crystal head is in good contact with the cat, you can see the cat's indicator, if the cat's indicator light is connected to the line, it will be skipped after confirmation. Whether your broadband was normal or newly installed before. If the newly installed bandwidth is too far away from the service provider, you can skip it if it was previously easy to use. For the last killer, contact China Netcom, if you do not go to the Internet, you are requested to return the money !!!!!!!!!!

Download and install the client of China Netcom or China Telecom.

1. Check whether the NIC light is on or whether there is a disconnect icon in the operating system.
2. Change the network cable to test whether the line is faulty.
3. Check your own IP address, gateway, subnet mask, DNS
4. For ADSL, check whether the password is incorrect Based on the dialing performance.
5. For ADSL, reset the cat settings and reset the VCI parameters.
6. If there is no response after dialing for a long time, ask the local communication department
7. Ping yourself to check whether local settings are correct.
8. Ping the gateway to check whether data can be connected.
If the above conditions are normal, your gateway will not be able to access the network. No!

Generally, the problem does not occur in the system, and restoration is useless.
Possible problems:
1. IP address is not set
2. Contact your ISP for account issues
3. Problems with hub, cat, and other devices

If the machine has a network cable and is connected to a network card, it cannot be connected to the network. If it is because you are connected to a LAN, there is no Internet port in the network. Or your network is improperly set.

There are many reasons why the computer cannot access the network, such as system problems (whether it is configured, such as IP settings), browser problems (incorrect settings or program file damage and virus interference) nic problems (whether damaged or conflict exists), driver problems (whether correctly installed), network cable problems (whether the crystal head has poor contact), and moden problems (whether damaged) ISP problems (server room faults) can be found only after step-by-step investigation. If you are not sure about the problem, you should look for a master.

Based on my company's experience, it is very likely that a vro or firewall is used to set policies, assign a fixed IP address to each computer, and then set which IP addresses can access the Internet in the policy, which are not allowed.
You can try to change your IP address to a manager or a developed IP address (provided that their computer is not powered on) so that you can access the Internet.
If you are using the 2000 or XP system, right-click your network neighbor and choose "properties"> "Local Connection"> "properties"> "Internet Protocol"> "automatically obtain IP, vrouters in many companies are set to automatically allocate IP addresses for DHCP, and sometimes they can access the Internet.

Q can be accessed, but the network cannot be connected.

This often occurs when you open ie. In the lower-left dialog box of the IE interface, the system prompts that the webpage is being opened, but the webpage does not respond for a long time. Check the process in the Task Manager (enter the method, place the mouse on the taskbar, right-click the Task Manager-process) to see how the CPU usage is. If it is 100%, you can be sure, if you want to run other programs, the virus is infected. Check which process occupies CPU resources greedily.

After finding it, you 'd better record the name and click "end". If it cannot be completed, you need to start to secure mode to delete the stuff and enter the Registry. (method: start-run, enter Regedit) in the Registry dialog box, click Edit-search, enter the program name, find it, right-click to delete it, And then perform several searches, it can often be completely deleted.

There are a lot of viruses. When anti-virus software is powerless, the only way is to manually delete them.

2. related to setting proxy servers

In some cases, the proxy server (control panel -- Internet option-connection-LAN Settings-use proxy server for LAN) is set in the browser ), setting the proxy server does not affect QQ's network connection, because QQ uses port 4000 and port 80 or 8080 to access the Internet. This is why many people do not understand why QQ can be accessed, but web pages cannot be opened. The proxy server is generally not very stable, sometimes it can be accessed, sometimes it cannot. If so, cancel the proxy.

Iii. DNS server explanation Error

Domain Name Server (DNS) converts a domain name to an IP address that can be recognized by a computer. For example, the IP address corresponding to the Shenzhen window (www.sz.net.cn) is 219.133.46.54, and the Shenzhen hotline (www.szonline.net) the corresponding IP address is 202.96.154.6. If an error occurs on the DNS server, the domain name cannot be interpreted. Naturally, the Internet cannot be accessed.

If this is the case, sometimes it is a problem with the network service access provider (ISP), you can call the ISP. Sometimes it is a problem with the vro or network card and cannot be connected to the DNS Service of the ISP.

In this case, you can turn the vro off for a while, or reset the vro. Or the network adapter cannot automatically find the DNS server address. You can try to use the specified DNS server address. In the network properties, (Control Panel-network and dial-up connections-local connection-right-click Properties-TCP/IP protocol-properties-use the following DNS server address ). Different ISPs have different DNS addresses. For example, China Telecom usually uses 202.96.134.133 (master) 202.96.128.68 (Backup ).

Updating the NIC driver or changing the NIC is also an idea.

Iv. Failure to start IE due to loss of system files

This phenomenon is quite common because:

1. system instability is manifested in frequent crashes, frequent inexplicable restarts, and illegal shutdown, leading to loss of system files;

2. Hardware and Software conflicts often occur when some programs are installed, causing NIC Driver conflicts or IE conflicts. Since Intel introduced hyper-threading CPU, an outstanding problem is that IE6 in XP SP1 conflicts with hyper-threading;

3. Virus intrusion causes damage or loss of system files.

In the first case, you can try to repair the system. In the 2 K or XP system, place the original installation disc (Note: The original installation disc must be used), and enter SFC/scanow in the Start-run mode, press enter. 98 systems can also be checked using the SFC command.

In the second case, You Can unmount the recently installed hardware or program. 2 K or XP systems can press F8 after the machine is started to enter the Start Menu, select "Last correct configuration". If it is an XP system, you can also use the restoration function of the system to solve the problem quickly.

If the XP system is caused by hyper-threading CPU, you can disable hyper-threading In the BIOS or upgrade to SP2. (Of course, upgrading SP2 in XP involves a lot of knowledge and precautions, which will not be detailed here ). In this case, the ttbrowser that comes with QQ can be browsed normally. You can try it again.

In the third case, the system disk should be thoroughly scanned for viruses.

Another phenomenon also needs to be paid special attention: You can open the homepage of the website, but you cannot open the second-level link. If so, you can re-register the following DLL file:

Enter:
Regsvr32 shdocvw. dll
Regsvr32 shell32.dll (note that you do not need to enter this command First)
Regsvr32 oleaut32.dll
Regsvr32 actxprxy. dll
Regsvr32 mshtml. dll
Regsvr32 urlmon. dll
Regsvr32 msjava. dll
Regsvr32 browseui. dll

Note: Press ENTER for each entry. The second command does not need to be input. After these commands are input, restart Windows. If it is invalid, enter the second command again. In addition, if it is a 98 system, it may be easier to download this file from the Microsoft website. The file is:

Http://download.microsoft.com/download/msn...us/mcrepair.exe

5. Damaged IE

If none of the above methods works, it may be that the kernel of IE is damaged. Although the system has been repaired and cannot be compensated, reinstalling IE is the best method.

For 98 or 2 k systems, if the IE version is 5.0, we recommend that you upgrade it to 6.0.

If 6.0 has been installed on the 98 system, click Add/delete programs in the control panel. A repair dialog box is displayed. Select the default repair and restart.

If it is a 2 K + ie6.0 or XP (the built-in IE is 6.0) system, re-ie is a little troublesome, there are two ways:
1. Open the registry, expand hkey_local_machinesoftwaremicrosoftactive setupinstalled COMPONENTS {89820200-ecbd-11cf-8b85-00aa005b4383}, and change the isinstalled DWORD value to 0;

2. Open the Windows XP installation disc and enter "rundll32.exe setupapi" and "installhinfsection defaultinstall 132% WINDIR % infie. inf" at the startup and runtime"

[Supplement] ping the website first. For example, if www.baidu.com is accessible but the website is not accessible, it indicates that it is not a problem with the host. Find another method. (To be resolved)

Ping 127.0.0.1 again, that is, your own machine. If it fails, it is a problem with the machine. Nic or network cable.