(The host PC1 can be used normally, but the network connected by PC1 has been intermittent, and the gap is about 30s-40s. The network connected by PC2 is normal. The lines from the switch to each PC are unified and controlled under the concrete floor for general wiring and cannot be replaced. After the instrument test, each circuit conforms to the fluke 6 standard, and the test is passed. Swap the positions of pc1 and pc2 (that is, connect PC1 to the network cable of PC2, and connect PC2 to the network cable of PC1), and both PCs can work normally.)