|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-
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-
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.