What is the backbone area in OSPF called?

• A. Area 1
• B. Area 0
• C. Area 2
• D. Area 3

Answer: (B)

OSPF uses a hierarchical design where all inter-area routing passes through a single central area, the backbone. This backbone is called Area 0. It acts as the hub that distributes summary routes between different areas, with Area Border Routers connecting non-backbone areas to it so information can flow from one area to another via Area 0. If a direct connection to the backbone isn’t possible, a virtual link can be used to maintain backbone connectivity through another area, but the core idea remains: all non-backbone areas rely on the backbone for inter-area routing.