Neighbor - A neighbor refers to a connected (adjacent) router that is running an OSPF process with the adjacent interface assigned to the same area. Neighbors are found by Hello packets.
Adjacency - An adjacency refers to the logical connection between a router and its corresponding designated routers and backup designed routers.
Link - In OSPF, a link refers to a network of a router interface assigned to any given network. Within OSPF, link is synonymous with interface.
Interface - An interface is a physical interface on a router. When an interface is added to the OSPF process, it is considered by OSPF as a link. If an interface is up than a link is up.
Link State Advisement - (LSA) is an OSPF data packet containing link state and routing information that is shared among OSPF routers.
Designated router - (DR) is only used when the OSPF router is connected to a broadcast (multi-access) network.
Backup Designated router - (BDR) is a hot standby for the DR on broadcast links.
OSPF areas - OSPF areas are similar to EIGRP Autonomous Systems. Areas are used to establish a hierarchical network. It uses four types of areas.
Area boarder router - (ABR) is a router that has multiple area assignments. An interface may belong to only one area. If a router has multiple interfaces and if any of these interfaces belong to different areas, the router is considered ABR.
Autonomous system boundary router - (ASBR) is a router with an interface connected to an external network or a different AS. An external network or AS refers to an interface belonging to a different routing protocol.
Non-broadcast multi-access - (NMBA) networks are networks such as Frame Relay, X.25, and ATM. This type of network allows for multi-access but has no broadcast ability like Ethernet. .
Broadcast (Multi-access) - Networks such as Ethernet allow multiple access as well as provide broadcast ability.
Point-to-Point - This type of network connection consists of a unique NMBA configuration.
