A Bit Mask indicating whether the router is forwarding IP multicast (Class D) datagrams based on the algorithms defined in the Multi- cast Extensions to OSPF. Bit 0, if set, indicates that the router can forward IP multicast datagrams in the router's directly attached areas (called intra-area mul- ticast routing). Bit 1, if set, indicates that the router can forward IP multicast datagrams between OSPF areas (called inter-area multicast routing). Bit 2, if set, indicates that the router can forward IP multicast datagrams between Auto- nomous Systems (called inter-AS multicast rout- ing). Only certain combinations of bit settings are allowed, namely: 0 (no multicast forwarding is enabled), 1 (intra-area multicasting only), 3 (intra-area and inter-area multicasting), 5 (intra-area and inter-AS multicasting) and 7 (multicasting everywhere). By default, no mul- ticast forwarding is enabled.