Cisco Certified Network Associate (CCNA) Practice Exam

Which marker denotes an NSSA External route in OSPF?

1. O*E

2. O*N

3. O

4. O*I

The correct answer is: O*N

In OSPF (Open Shortest Path First), the marker that denotes an NSSA (Not-So-Stubby Area) External route is indeed represented by "O*N." This notation indicates an external route that is allowed to be injected into a Not-So-Stubby Area, which can happen under specific configurations where the NSSA can import external routes while still retaining some characteristics of a stub area. In this context, the "O" signifies that the route is an OSPF route, while the "*N" designates that the route originates from an external source and is recognized as an NSSA external route. This differentiation is crucial for OSPF routing, as it allows administrators to manage how external routes are propagated within various area types while controlling routing updates and efficiency. Other notations, such as "O*E" represents an external route in a regular OSPF area, but is not applicable to an NSSA, while "O" denotes a standard intra-area route. "O*I" signifies an inter-area route, which refers to routes between different OSPF areas, but similarly does not apply to NSSA routes specifically. The understanding of these notations is essential for configuring and troubleshooting OSP