Specific process of resolving the problem of being able to ping the gateway but not surfing the internet

Two such problems occur: ADSL can be connected normally, but the Internet cannot be accessed after connection. Ping the command to ping the gateway. Fans
Cause: the Winsock2 fault or the file is damaged.

Solution: Use the Super Rabbit ie repair expert, which has a tool "strong repair Winsock2". Click Run To fix Winsock2. Restart your computer to access the Internet.
(If not, reinstall the system .)

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In general, the failure to ping the gateway but not to access the Internet is caused by DNS Service faults. In rare cases, you can check the firewall and proxy settings. In addition, what else will this happen? The example below may not be noticed, but it appears more and more frequently in our network, and we have to pay attention to it.

The first thing we can determine is that the network hardware (NIC vro) works normally when the gateway can be pinged, and the software setting has become the focus of our troubleshooting. The following describes the specific process.

The 10.0.87.x CIDR block was found to be abnormal at the beginning of 2006.8.11, and intermittent network failure. Fault: The machine can access the Internet normally before, and suddenly the machine can ping the gateway and cannot access the Internet. After a while, the network will recover to normal, and then the machine will fail again, this is repeated. After multiple detection found: when the network is not connected, ARP table exception, the specific situation and troubleshooting method is: Enter the MS-DOS window, enter the command: ARP-A (view the local ARP table ), record the correct MAC address corresponding to the gateway IP address when the network is connected. If the network fails, enter the command ARP-A again to view the ARP table, compared with the ARP table, we found that the gateway ip10.0.87.1 is supposed to correspond to the MAC address of the switch. When the network is abnormal, the gateway ip10.0.87.1 error corresponds to the MAC address 00: 0a: E6: 94: F5: Ca (globally unique identifier) as a result, all the data sent in the CIDR block will flow to the user. After the problem is found, the ARP table when the network is normal is the MAC address of the home computer of the family's Master Wang beauty instructor. the user's valid IP address is 10.0.87.small (we use a static IP address ), her Nic Mac is 00: 0a: E6: 94: F5: Ca (I have made a record for this job). Here is the client's computer, ask about the situation, and solve the problem.

Later, I learned that I was able to eliminate the possibility of personal malicious attacks through on-site troubleshooting. It was initially determined that the virus was infected with a Trojan-like spyware and that the virus had escaped the scanning and removal of trend-oriented antivirus software. It is estimated that the virus attack principle is as follows: after obtaining control of a computer in a LAN, use the underlying arp/RARP protocol to obtain the IP address and MAC address of the gateway, in this way, you can disguise yourself as the IP address and MAC address of the gateway, causing chaos in the LAN. All data packets in the network segment are captured by yourself, and then analyze the unobtained data packets, in order to obtain useful information such as the account and password of other users on the Internet, the eavesdropping behavior of this virus may cause serious losses to other users on the network, for example, it is possible to steal information such as online bank accounts, so we must improve the vigilance.

The key to solving this problem is to enhance user security awareness, not to browse malicious sites and pages, not to download and install various unknown plug-ins, especially not to download and install software that you do not know, and to install anti-virus software, enable monitoring and timely update the anti-virus database to block most virus attacks. Once an attack is detected, it is also critical to quickly identify infected users to reduce or avoid losses as much as possible. After all, there is no absolute security. We can see that some of the data collected at ordinary times plays a key role in Fault Locating. At one time, we need to keep some seemingly useless network cabling materials, such as topology charts and wiring tables, VLAN and IP Address Allocation Table. You can regularly record the MAC address table in the network to find out which computers are new to the network.

Prevention Method: Install anti-virus software and ensure that the anti-virus software works properly. I once met two examples in the academic affairs office of our school where the virus was modified and the antivirus software was successfully controlled to escape the virus. To avoid such problems in our school, You can bind a MAC address. If the implementation is inconvenient, you can consider replacing it with a vswitch that can be managed by the network, so that you can isolate the user in time without affecting other users.

_________ Simply put, it is an ARP attack. Now we can use 360arp or Jinshan's arpfirewall!