Again, network disconnection is caused by poor network cables.

At present, many small and medium-sized enterprises have similarities in their network environments. If the network quality is not good, there will often be chaos. I have experienced such a thing.

The network of the organization where the author is located is like this: a network cable + an ADSL Router + A multi-port Hub, and several shared Internet PCs are connected to the Hub. Due to the increasing number of people accessing the internet and the insufficient Hub ports, coupled with the inherent performance defects of the Hub, the network became increasingly overwhelmed. So I used a switch to replace the original Hub. After a try, the network speed was much faster. The speed of the network is faster, but the problem has also emerged. Several employees clamored that they could not access the network, and I began to solve the problem.

Ping the lan ip address of the vro from these PCs, but Ping other hosts on the Internet. At that time, it was also considered that the quality of the RJ-45 head of the network cable was not close, it was damaged when the switch was switched into the network cable. But looking at the indicators on the corresponding port on the switch, there are four or five computers that cannot access the Internet normally. The indicator on the switch port connected to only one PC is abnormal, it seems that the network cable is faulty. The switch port indicators connected to several other PCs are normal, indicating that the M indicator and the Link lamp in the connection status are on. Looking at the computer's Nic, the indicator is also normal, which indicates it does not seem like a network cable problem. The IP address of the local machine is pinged, but other hosts in the network cannot be pinged. On a vswitch, the connection ports of the computers that cannot access the Internet normally are switched. This still exists, indicating that the vswitch port is not faulty. Check repeatedly to identify the cause. Some people say that there is a problem with the new switch because they are eager to access the Internet. Although I do not think it is a problem with the switch, I cannot find the reason, I had to connect the original Hub and connect those computers to the Hub as they meant. unexpectedly, the problem was solved!

Is it really a vswitch problem? Why can't I connect to a Hub without a vswitch? Consider the differences between the Hub and the switch, and think the most suspicious is the connection rate, because the Hub is a 10 M connection rate, and the switch is 10/100 M Adaptive. When these machines connect to a vswitch, the connection speed is 100 M, which is the most obvious difference between the Hub and the vswitch. In other words, when the communication fails, the connection speed is 100 M, and the connection speed is 10 M during normal communication. Is the network cable quality poor and cannot be connected at M?

Therefore, check the NIC settings of a computer that cannot access the Internet normally. the duplex mode is "AUTO-SENSE", which is also the default setting of the 10/100 M rate adaptive Nic. Set it to the "10 M, FULL" mode, and connect it to the switch again. Everything will be "OK" immediately. In addition, the M speed indicator of the switch is not on, and the connection rate is 10 M after automatic negotiation.

So far the problem is clear: due to the poor network connection speed of less than MB, it can only run at a rate of 10 MB, leading to this strange phenomenon. The current 10/100 M Adaptive nic and vswitch both have the automatic negotiation function. When you start the connection, first determine the connection rate. Only when both sides can run at M speed can the connection be connected at a speed of MB; if one is 10 m, it is connected at 10 m. Then determine the transmission mode to see whether it is full or half duplex. The selection principle is the same as the selection rate. In this example, when both parties negotiate the rate, because both sides are 10/100 M, full duplex adaptive, so select the connection rate of 100 M, full duplex. However, due to poor network cable quality, communication fails. Therefore, the network card speed can only be forced to 10 M on the computer, so that the two sides connect at 10 M rate, in order to communicate normally.

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