Signs That an Ethernet Cable Isn't Working Rightby Dan Stone
A bad Ethernet cable shows many of the same symptoms that other network hardware failures demonstrate; however, the cable is often to blame when the problem is isolated to a single computer or device. When an Ethernet cable isn't working correctly, the rest of the network will still function correctly. Any type of service disruption or slow performance can trace back to a faulty Ethernet cable.
Cable Loses Connection
A failed network connection could implicate the Ethernet cable. If you plug the cable into the Ethernet adapter and the light doesn't turn on, it could indicate a problem with either the cable or the adapter itself. An Ethernet cable that has failed will also trip error messages within the operating system: if the Windows Taskbar pops notification messages that claim the network connection has been lost or displays the "No Connection" icon on the taskbar, check to make sure the cable is properly connected -- a bad cable will not work when properly connected. If all computers are losing Internet connectivity, check the cables between the network switch and router or router and modem.
Intermittent and Slow Connection
If the connection on a single network device keeps dropping in and out or runs very slowly, the cable might be damaged. Wear and tear on the cable itself can break down the internal wire connection and lead to a shoddy connection. If the cable is bent, it may break apart the wire and cause the connection to be unstable. If the cable is bent or worn, physically straightening the cable with your hands may solve the problem. However, if the cable is too beat up it will have to be replaced.
Connection Restored with a Wiggle
If wiggling the cable re-establishes a failed connection, you may have a broken cable connector on your hands. Ethernet cables feature a built-in plastic lever that secures the cable into place within the Ethernet adapter port. If the lever breaks, the connection is only maintained through gravity and will drop out if the cable is moved out of place. Without the lever to locking the cable in place, the tiniest of movements can interrupt the connection.
Replacing the Cable Resolves Problem
The ultimate sign that an Ethernet cable is not working correctly is if you replace the cable with a different one and all of the problems go away. Replacing the cable eliminates all other Ethernet hardware as the cause of the problem: if the problem persists with the new cable, the cable is not the part of the network that's malfunctioning. However, replacing the cable may not be easy to test if the Ethernet cable is particularly long and runs through obstructions like walls.
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