Cisco Certified Network Associate (CCNA) Practice Exam

Which type of OSPF area allows only LSA's of types 1, 2 and 7?

1. Totally NSSA

2. Stub area

3. Totally stubby area

4. Not-So-Stubby-Area

The correct answer is: Totally stubby area

The correct answer is the Totally Stubby Area. In OSPF (Open Shortest Path First), a Totally Stubby Area is an area that restricts not only external routes but also inter-area routes from being sent into the area. This results in the area being able to learn only Type 1 (Router LSAs), Type 2 (Network LSAs), and Type 7 (LSA for NSSA configuration) link-state advertisements. The hallmark of this area type is that it abstracts away the external routes, simplifying the routing process and reducing routing table size. In contrast, a Stub Area allows Type 1 and Type 2 LSAs but does permit Type 3 (Summary LSAs) from other areas. Therefore, while it limits certain types of LSAs, it does not restrict Type 3 LSAs like a Totally Stubby Area does. A Not-So-Stubby-Area (NSSA) permits Type 7 LSAs as well but is designed to accommodate external routes mentioned in another area, making it more flexible than a Totally Stubby Area. Lastly, a Totally NSSA area is focused on a similar principle to a Totally Stubby Area but allows Type 7 LSAs. Hence, it does not