This managed object is a filter used for identify the target from which the MAC addresses are learned in macTable. The target could be: 1: Subtending port 1 2: Subtending port 2 3: Uplink port 1 4: Uplink port 2 5: All of the four uplink ports 6: All ports in the system IfIndex is used for identifying subscriber ports (e.g. 300 means all ports in slot 3 and 301 means port 1 in slot 3).