This is a running count of received frames on an interface that are not a whole number of octets in length and also fail the frame check sequence. Admins watch this counter for signs of physical-layer problems like bad cabling or a failing NIC, since alignment errors typically indicate a corrupted signal. A steadily climbing etherAlignmentErrors count on one port, while other ports stay at zero, points the admin toward a cabling or hardware issue on that specific link.