This gives the specific logical interface index where this MAC address entry was learned, to be interpreted according to the interface type reported in cienaCesMacScanLiType. An admin needs this index together with the type field to actually pin down which physical port or tunnel a suspicious MAC address came in on, since the index alone is meaningless without knowing what kind of interface it refers to. For example, an index of 14 combined with liType port(2) tells the admin to look specifically at logical port 14.