This read-only integer counts frames received on the BOOTPC or BOOTPS port whose operation code field was neither a BOOTREQUEST nor a BOOTREPLY, causing the frame to be discarded. An administrator treats a nonzero count as evidence of malformed or non-BOOTP traffic hitting these UDP ports. For example, a persistent statBootpInvalidOpCodeField count could indicate a misconfigured device or a scanning tool sending garbage packets to the BOOTP ports.