The MIB_BEST_IF structure stores the index of the interface that has the best route to a particular destination address.
typedef struct _MIB_BEST_IF {
DWORD dwDestAddr; // destination address
DWORD dwIfIndex; // best interface for that dest addr
} MIB_BEST_IF, *PMIB_BEST_IF;
Windows NT/2000: Requires Windows 2000.
Header: Declared in Routprot.h.