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.
In a real-world networking environment, you will be expected to be able to troubleshoot client connectivity in many different areas. The following sections provide some troubleshooting checklists that can help you review some of the various troubleshooting areas.
Troubleshooting Cabling Problems
Cable accounts for a great many of the problems on a network. There are many places to look when you suspect a cable-related problem. If you suspect that cable is at the bottom of your network troubles, consider the following areas:
Loose connections You need to verify that cables are securely attached and that they are attached to the correct ports.
Poorly crimped or bent cable Sometimes a chair running over a cable or a cable that has a poor crimp can cause problems.
Incorrect cable length Recall from that cables cannot exceed a specified maximum length.
Cable placement Care must be taken when cables are run too closely to strong electrical devices. If cables are run too closely to electrical devices, you need to ensure that they are designed for the task.