pdnDot1dTpPortInDiscards is a read-only Counter of frames received on this port that were discarded (filtered) by the Forwarding Process. Admins monitor this to detect a port whose traffic is being actively filtered, which could indicate a misconfigured filtering rule, a security policy in effect, or a spanning-tree blocking condition. For example, an unexpectedly high pdnDot1dTpPortInDiscards count on a port that should be passing normal traffic would prompt an admin to check that port's filtering configuration.