Cisco Certified Network Associate (CCNA) Practice Exam

What is the purpose of a Type 3 LSA in OSPF?

1. To describe external networks

2. To describe summary routes to neighboring routers

3. To identify all routers in a segment

4. To provide default routing information

The correct answer is: To describe summary routes to neighboring routers

A Type 3 LSA, also known as a Summary LSA, is utilized in OSPF (Open Shortest Path First) to share summary routing information within an OSPF area, specifically between different OSPF areas. Its primary purpose is to convey summarized route information from one area to another, allowing routers in different areas to understand reachable networks without requiring detailed information about every individual route. This helps optimize the OSPF routing table and reduces unnecessary routing information, thereby enhancing the scalability of the OSPF protocol in larger networks. In the context of OSPF, Type 3 LSAs are crucial for maintaining efficient routing and are mainly used by Area Border Routers (ABRs), which connect one OSPF area to another. By summarizing routing information and reducing the amount of data exchanged between areas, Type 3 LSAs facilitate a more efficient and manageable OSPF routing infrastructure.