A cooling fan problem for the CPU in the PC or the network switch. It is rattling like crazy and driving you up the wall.
You can either buy a new replacement, fan or re-oil the fan.
Yes, that is right re-oil the fan. After some time, eg years the lubricating oil in the spindle evaporates off. To re-oil, you need to first disconnect the fan from the equipment. This is usually easier said than done. Some network switches have hidden latches that need to be carefully pried open.
After taking out the fan, look closely at the center of the fan. There is a large round metallic sticker with all the product information.
Using a penknife, carefully lift up the sticker. You should see a hole or depression where the spindle is. Drop a few drops of light lubricating oil. Be careful not to get any oil on the sticker. Re-seal with the sticker.
Power on, the fan should sound as good as new.