problem
When we encounter a network failure, such as the Internet does not even open when the browser can not access other issues, we should be how to troubleshoot it?
Our first thought is the physical layer, as in the physical layer of the OSI reference model is the most low-end, the most basic.
Physical layer troubleshooting
The main view the connection status, send and receive data packets
1. The cable is connected or not
We open the Control Panel -> Network and Internet-> Network connection (or "Change Adapter") we can see multiple network connections
If this occurs, it is clear that the physical layer is the cable is not connected or released due to failure
2. Crystal Head Fault
If this occurs, data packets sent but not received, this may be the problem of network cable Crystal Head
Because the crystal head has eight lines, four is sent, four are accepted, if there is not sending reception is likely to be crystal head is bad, needs to be redone
The data link layer troubleshooting
1.MAC address conflict
In general, the computer MAC address is unique, but someone changes their MAC address in the registry which under certain circumstances, lead to conflicts with other MAC address, and thus can not connect to the Internet
2.ADSL arrears (such as dial-up arrears)
When the local physical interface no problem, but not on the network, there may be network arrears, resulting in operators disconnect the data link layer, the network layer, thus affecting the normal communication
3. The computer is connected to the wrong VLAN
Create a switch above VLAN1, VLAN2, under VLAN1 computer to connect to the network VLAN2, which is the data link layer failure
Troubleshoot the network layer
1.IP address, subnet mask error
Generally, a computer network are first planned, in which a good division of the computer network of switches which belong to the computer on the network segment to segment according to the corresponding address allocation, the address, such as a computer network was changed to 15 16 segment address, network layer will lead to error
2. Path, Gateway error, the router is not configured route to the destination network
If the computer does not have a gateway configuration, you can not select the path to other networks, this is a problem selected path
In addition, if the router on the Internet fails, the most likely cause data to be discarded
Troubleshooting application layer (where the above network layer to the application layer are divided)
1. The application configuration error
For example, I open the browser, the Internet can be normal, but my network configuration settings to the browser and let the browser to find a proxy server that does not exist online, this time can not necessarily access