Cracking DHCP Network Services

Recently, when an anti-virus software installed on Windows XP is forcibly uninstalled, it finds that the laptop suddenly cannot access the Internet, opens the network neighbor attribute window, and checks the properties of the local connection, the IP address in the TCP/IP parameter settings interface is changed to "0.0.0.0 ". However, I have previously set the IP address of my notebook to be dynamically obtained. I have not made any changes to the network parameters. How does the IP address change to "0.0.0.0?

When I search for the "0.0.0.0" address on the internet, I find that this address does not represent any computer or network. Obviously, the IP address of the Local Computer is "0.0.0.0 ", it indicates that the local network interface has not been properly opened, that is to say, the laptop has not obtained a real and valid IP address from the DHCP server, so the laptop will naturally fail to access the Internet.

So why does the IP address of the Local Computer change to "0.0.0.0? Considering that the IP address has not changed any network parameters before and after the mutation, and the Internet access is normal before the anti-virus software is uninstalled, IP address mutation must be caused by this anti-virus software. In order to further verify the author's guess, I opened the windows xp system log information and found some answers.

Sure, the log file clearly prompts that the system has a 7300 error and the DHCP service cannot be started normally. In order to find out the cause of the 7300 error, I went to the Internet to check the relevant information. After several efforts, I finally realized that the 7300 error was mainly caused by the failure of the DHCP Client Service to initialize normally, once the DHCP service cannot be properly started, Windows XP wks cannot dynamically obtain valid IP addresses from the DHCP server. This is obviously why the IP address of the Local Computer suddenly changes to "0.0.0.0.

According to the prompts in the log file, I further found that the reason why the DHCP Client service cannot be normally initialized is mainly because the symtdi service that is dependent on the DHCP service cannot be started normally. The symtdi service is automatically monitored when many anti-virus software are running. Once the anti-virus software is forcibly uninstalled, The symtdi service will be affected and cannot be started normally.

To enable the DHCP service to start normally, you can remove the dependency between the service and the symtdi service. To do this, follow these steps:

Click Start or run. In the displayed system running dialog box, enter the string command regedit and click OK to open the registry editing window;

Expand the Registry branch HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ DHCP in sequence. In the subwindow on the right of the corresponding "DHCP" branch, double-click the "dependonservice" key value, in the attribute setting box that appears, delete the symtdi value data, click OK, and restart the computer system. In the future, follow the normal method and reset the Internet access parameters to ensure that the local computer can access the Internet normally.