In addition to point-to-point and broadcast networks, OSPF can operate in non-broadcast multi-access (NBMA) mode.
An NBMA segment emulates the function of a broadcast network. Every router on the segment must be configured with the IP addresses of each of its neighbors, and may need to be configured with the MAC address of its neighbor if the network does not support Layer 2 broadcast. OSPF Hello packets are transmitted individually as unicast packets to each adjacent neighbor. Because an NBMA network has no broadcast or multicast capabilities, the routing device cannot discover its neighbors dynamically, so all neighbors must be configured statically.
As in a broadcast network, a designated router and a backup designated router are elected when OSPF is operating in NBMA mode. The designated router is similarly responsible for sending link-state advertisements (LSAs) for the network.
OSPF does not support NBMA interfaces that are part of a multi-area adjacency. An interface can either be in multiple areas or in NBMA mode.
OSPFv3 sends Hello traffic to IPv6 link-local addresses and neighbors must be statically configured using their IPv6 link-local address.
OSPF NBMA is supported on Ethernet ports only.