What's going on with the D-link DES-3540 switch?

Question

Computer networks

The network configuration has not changed for a long time. Began to reduce the speed on three computers to 10Mbps (according to the IAC) - I replaced the network card. After 3-4 days, two other computers became completely offline. I looked at the log on the switch of such a computer, which is completely offline. In logs writes the port is connected-port is disconnected in a cycle. I did not find a list of blocked MACs in the settings. Resetting to factory settings does not help. I went into the settings only through the web 10.90.90.90.

Answer 1

In logs writes the port is connected-port is disconnected in a cycle.

There is a physical loss of the link. Two options.
1. ports on the switch are dying; solution: replace the switch;
2. the bundle of cables was immediately damaged (bitten by rats, damaged during construction and repair work, trampled under foot in case of open laying (unlikely), slight damage to the outer sheath + moisture ingress under the sheath, exposure to high temperature from heating pipes passing nearby (as a result of PVC - insulation crumbles), prolonged exposure to UV from direct sunlight (unlikely), etc., etc.); solution: find the cause of the damage, eliminate the cause, then lay new cables.

Answer 2

If the wires are normal and the computers are normal, then the switch is buggy.
In access switches, the ports on the board are grouped in groups of eight. One ASIC handles eight ports. It is quite possible that a specific asic dies. Try to poke problematic PCs into another eight.
In switches, there is such a problem as a collision of poppy addresses. The switch looks for the port where to send the packet, according to the hash from the poppy address and vlan. First, a pair of hashes can match. Secondly, the memory for storing these hashes (tables of poppy addresses) is expensive, and manufacturers of cheap switches save on it so that it does not fit the entire hash, but only its first bytes. This feature can also lead to collisions. You can try to transfer ports to another vlan. Or find the poppy address due to which the collision occurs.
And of course, no one canceled the case when several devices appeared on the network with the same poppy address (or a loop), and the switch ports flap due to loop-detect.

Answer 3

Ports could burn out due to static. The reasons may be different, for example, they laid carpet in the office, people began to shuffle their feet, generating a charge.
Also because of the potential difference on the switch and computer cases. For example, there used to be one ground bus, and then it was completely removed or smashed.
I'm not sure about the electrolytes in the switch, but it's worth checking them.