Question

Which of the following statements is/are INCORRECT about the OSPF (Open Shortest Path First) routing protocol used in the Internet?

• A. OSPF implements Bellman-Ford algorithm to find shortest paths.
• B. OSPF uses Dijkstra’s shortest path algorithm to implement least-cost path routing.
• C. OSPF is used as an inter-domain routing protocol.
• D. OSPF implements hierarchical routing.

Hint:

Remember: OSPF is a link-state routing protocol using Dijkstra’s algorithm and works as an intra-domain protocol. Bellman-Ford is for RIP, while BGP is used for inter-domain routing.

Answer 1

The Correct Option is A

Statement (A): Incorrect.
OSPF does not use the Bellman-Ford algorithm. Bellman-Ford is used by distance vector protocols like RIP (Routing Information Protocol). OSPF is a link-state protocol and uses Dijkstra’s algorithm. Hence, this statement is False.
Statement (B): Correct.
OSPF is based on link-state routing and indeed uses Dijkstra’s shortest path algorithm to calculate least-cost paths from source to all other nodes in the network. Hence, this statement is True.
Statement (C): Incorrect.
OSPF is an intra-domain (or interior gateway) protocol, used within an Autonomous System (AS). Inter-domain routing protocols are BGP (Border Gateway Protocol). Hence, calling OSPF inter-domain is False.
Statement (D): Correct.
OSPF allows hierarchical routing by dividing the network into multiple areas. This reduces routing overhead and improves scalability. Hence, this statement is True.
\[ \boxed{\text{Incorrect Statements: (A) and (C)}} \]