This rolls together the various classes of errored frames -- CRC, alignment, and other receive faults -- received on this interface into one count. Treat it as a trigger rather than a diagnosis: a nonzero and climbing RxInErrorPkts for the current, still-accumulating short interval bin on this port means it's time to check the more granular RxCrcErrorPkts, FragmentsPkts, and JabbersPkts counters for the same interface to isolate which failure mode is actually occurring. For example, RxInErrorPkts rising to 28 for this in-progress short-interval bin on a port whose RxCrcErrorPkts rose by almost the same amount would point squarely at a physical-layer problem on that one link.