LANs, like all hardware elements, need to be checked and scanned every so often, to verify and check they are working perfectly. To do this you just need a tool like Advanced LAN Scanner.
Advanced LAN Scanner is a program, totally free, that exhaustively checks all the elements that make up a LAN, detecting and verifying if each port is working. In the check it also extracts information on users of that LAN, of services, of shared information, etc.
From Advanced LAN Scanner you can also access the content of any machine connected to the LAN.