Do not connect a common PC to a layer-3 Switch at any time

Case:
There are two PCs at the front-end. After Windows 7 is started and the password is entered, the desktop file cannot be displayed (the desktop file is roaming on the win2008r2 server). In the lower-right corner of the screen, the Network Disk cannot be accessed. Refresh the desktop file.
Analysis:
The Network Disk prompts that it cannot be accessed because of two reasons. I. Hardware problems. Here the hardware mainly refers to the network. 2. software problems. There is no third-party software involved here. The system itself is the object of our inspection.
Solution:
1. view the IP address and DNS of the PC. The result is normal.
2. Ping DNS and ping the file server. Communication is normal.
Preliminary conclusion:
The network is normal. Is the problem in the PC system or hardware?
Re-processing:
Move the PC to the network management office to access the network. The above problems did not occur.
Again concluded:
The PC itself and the system are okay, and the problem is obviously on the network.
Next steps:
1. Find the PC network port and the connected switch. It is a layer-3 Switch of Huawei 5700 In the IDC.
2. Go to Huawei 5700 and check the port status. An exception was found at a rate of 100 MB. It should be MB.
3. view the PC Nic status. The speed is 1 GB. An exception occurs here.
Diagnosis:
The switch speed is inconsistent with that of the PC.

Final processing:
1. Cancel the automatic negotiation function for the PC port corresponding to the layer-3 switch. (UNDO negotiation auto)
2. Set the speed of the switch to 100 m and duplex to full duplex.
3. Set the PC speed to 100 m. The duplex is in the same status as the switch. (Why not set MB? Actually, I first set m and the communication failed)
Final result:
The system prompts that the Network Disk cannot be accessed and the desktop cannot be displayed.

Finally, why is the network status of the switch different from that of the PC?
There is a process above, that is, when I connect a PC to the network management office, the problem will not happen. Why is the network environment of the network management office different from that of the foreground? The switch is automatically negotiated with the PC, and there is a problem with the negotiation here. As a result, the rate of the switch is inconsistent with that of the PC. I checked that the NIC Driver of the PC is the latest. Obviously, the NIC is compatible with the L3 switch. Later, I tried to connect my PC to another layer-2 switch and found that the problem would not occur?
Conclusion: Common NICs may have some invisible problems, and the compatibility is not good. The communication mechanism of a layer-3 switch is more complex than that of a layer-2 switch. Generally, it is only suitable to connect to a switch or server. It is not recommended to connect to a common PC.

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Do not connect a common PC to a layer-3 Switch at any time