OSPF in the context of inter-area routing, which component is responsible for distributing information between areas?

• A. Backbone
• B. Area Border Router
• C. Link-State Database
• D. Neighbor List

Answer: (A)

Area Border Router is the component that distributes routing information between areas. In OSPF, areas are used to scale the routing database, and each ABR connects one or more areas to the backbone (Area 0). The ABR maintains separate link-state databases for each connected area and generates inter-area routes by advertising summary routes (Type-3 LSAs) into the areas it touches, effectively propagating reachability information from one area to another via the backbone when needed. The backbone serves as the central hub all areas connect through, but it is the ABR that performs the actual inter-area distribution. The Link-State Database is kept separately per area and is not used to transfer information between areas, and the Neighbor List only tracks adjacencies with directly connected routers.