Physical Connectivity Errors
Although many of the problems associated with client connectivity can be traced to software-based problems such as configuration, authentication, and permissions issues, physical connectivity is often the root of the problem.
When you are troubleshooting physical connectivity errors, the first place to look is at the network cables. Although it is rare, cables can become loose or disconnected from NICs or from the ports on a hub or switch. Oftentimes, this is the result of other cables being plugged in or unplugged, or of other activity on the connections around the one that is having the problem. Other cable considerations include exceeded maximum lengths, cable breaks, and improperly terminated or made cables, although these are only a consideration in exceptional cases.
Physical connectivity errors also involve the devices used to establish the physical client/server connectivity. This can include hubs, switches, MSAUs, NICs, routers, and connectivity hardware. Although it is possible to have a problem with a single port on one of the aforementioned devices, it is more likely that the entire unit will malfunction. Thankfully, networking devices are very resilient devices that provide many years of service with few or no problems.