Check if a NIC is taking errors

The sources of these errors can vary, the most common of which are speed/duplex misconfiguration and faulty cables or hardware. So if you are troubleshooting weird network-related issues, it's a good idea to make sure your NIC isn't taking errors.

Windows

netstat -e | findstr /i "errors"

Linux

ifconfig | grep --color='always' -E "errors|$"