This enumerated object, blocked, multicast, or unicast, controls how multicast traffic is forwarded on this interface, noting that data-link multicasting is meaningless on point-to-point and NBMA interfaces where setting it to blocked effectively disables multicast forwarding there. It lets an admin tune multicast behavior per interface type rather than assuming one behavior fits all link types. An admin running OSPF multicast extensions over a point-to-point link would confirm this is set to unicast rather than the LAN-oriented multicast setting.