300-420 Question 108
Single answerYou are designing a Layer 3 infrastructure for a multicampus network that consists of three campuses: Campus A, Campus B, and Campus C. The campuses need to communicate with each other using optimal routing paths while maintaining scalability and fast convergence. Each campus has its own Layer 3 routing domain. Which design approach is most appropriate for this scenario?
- A
Implement a single OSPF area across all campuses to ensure optimal routing and convergence.
- B
Deploy an iBGP overlay with route reflectors to manage intercampus routing.
- C
Use EIGRP with separate autonomous systems for each campus and redistribute routes at the border routers.
- D
Design with OSPF multi-area configuration, assigning each campus to a separate OSPF area and using Area 0 as the backbone.
Show answer and explanation
Correct answer: D
Explanation
In a multicampus Layer 3 design, scalability, fast convergence, and optimal routing are critical objectives. OSPF multi-area design is well-suited for such environments because it segments the network into smaller, manageable areas while using Area 0 as the backbone for inter-area communication. This approach minimizes the impact of routing changes, ensures optimal routing paths, and maintains scalability in growing networks.
- A. Incorrect.
Using a single OSPF area across all campuses would not scale well as the network grows. It also increases the size of the link-state database, which can affect performance and convergence times.
- B. Incorrect.
Deploying an iBGP overlay with route reflectors is more suitable for service provider or very large-scale enterprise environments. It adds unnecessary complexity in this case and does not align well with the requirements for scalability and fast convergence in a multicampus design.
- C. Incorrect.
Using EIGRP with separate autonomous systems and redistributing routes introduces complexity and potential issues with suboptimal routing or route redistribution errors. It is not the best practice for a multicampus design.
- D. Correct.
Using OSPF multi-area configuration with each campus in a separate area and Area 0 as the backbone ensures scalability by limiting the size of the link-state database within each area. It also provides fast convergence and optimal routing paths by leveraging OSPF's hierarchical design.