Cisco Certified Network Associate (CCNA) Practice Exam

Which of the following options best describes a Router LSA?

1. It contains the full path to the destination network.

2. It lists all reachable routers in the area.

3. It does not cross the boundary of an area.

4. It is used only for OSPF internal routing.

The correct answer is: It does not cross the boundary of an area.

A Router LSA (Link-State Advertisement) is indeed a fundamental component of OSPF (Open Shortest Path First) routing. It is used primarily to convey information about the state of a router's links to other routers within the same area. The characteristic that best describes a Router LSA is that it does not cross the boundary of an area. This means that the information contained within a Router LSA is limited to the local area, ensuring that OSPF maintains a clear and efficient routing structure. The aspect of not crossing area boundaries helps in controlling the routing domain and optimizing the routing process, as it prevents unnecessary routing information from entering other areas which could lead to inefficient routing and increased complexity. Each area maintains its own Router LSAs, contributing to the overall stability and efficiency of the OSPF protocol. The other options do have relevance to OSPF and its operations, but they do not accurately define the nature of a Router LSA. For example, while a Router LSA does help convey information about routers, it does not carry a list of all reachable routers nor does it depict a complete path to a destination network, as those functions are covered by other types of LSAs. Additionally, while Router LSAs are integral to