300-420 Question 18
Select 4An organization is designing a scalable and secure OSPF routing architecture for its enterprise network. The network consists of multiple branches, two data centers, and a core layer. The design requirements include minimizing routing table size, ensuring fast convergence, and enhancing security by limiting external route advertisements. Which of the following design choices should be implemented to meet these requirements?
- A
Use OSPF stub areas in branch sites to reduce routing table size.
- B
Configure OSPF authentication to secure routing updates between all routers.
- C
Deploy OSPF virtual links to interconnect all areas directly to the backbone area (Area 0).
- D
Summarize routes at area boundaries to reduce the size of routing tables in other areas.
- E
Use OSPF totally stubby areas in branch sites to limit external route advertisements.
Show answer and explanation
Correct answers: A, B, D, E
Explanation
To create a stable, secure, and scalable OSPF routing design, it is essential to use features like stub or totally stubby areas to reduce unnecessary routing information in branch sites, configure OSPF authentication to secure routing updates, and apply route summarization at area boundaries to minimize routing table size and improve convergence. Virtual links, while useful in some scenarios, are not suitable for this design as they introduce complexity and do not align with the stated requirements.
- A. Correct.
Using OSPF stub areas in branch sites helps reduce the size of routing tables by blocking external routes and only allowing intra-area and default routes. This is an effective strategy for scalability in branch environments.
- B. Correct.
Configuring OSPF authentication enhances security by ensuring that routing updates are exchanged only between trusted routers, thereby preventing unauthorized or malicious updates.
- C. Incorrect.
Deploying OSPF virtual links to interconnect all areas to Area 0 introduces unnecessary complexity and potential points of failure, which contradicts the requirements of scalability and fast convergence.
- D. Correct.
Route summarization at area boundaries reduces the size of routing tables in other areas, which contributes to scalability and faster convergence by reducing the impact of topology changes.
- E. Correct.
Using totally stubby areas in branch sites limits both external and inter-area route advertisements, providing a highly scalable and secure solution for environments with limited routing requirements.