This read-only enumerated INTEGER (sentToCPU/discard) reports what the switch does with IPM multicast traffic that arrives on an illegal input port for this forwarding entry, i.e. a port not expected to source that stream. Admins care because sentToCPU means such traffic gets escalated to the control plane (useful for logging or further processing), while discard means it's silently dropped. For example, if a rogue device on an unauthorized port starts sending multicast traffic matching this entry, this field tells the admin whether that traffic would be logged via the CPU or simply vanish.