300-420 Question 17
Single answerYou are designing an OSPF routing architecture for an enterprise network with multiple branch offices connected to the core network. The branch offices have limited resources and must not be overwhelmed with OSPF updates. Additionally, the design must ensure scalability and secure routing. Which approach should you take when configuring the OSPF design?
- A
Configure the branch offices as OSPF Totally Stubby Areas (TSAs) and use area authentication.
- B
Configure a flat OSPF area design across all branches and the core network.
- C
Use OSPF virtual links to connect all branch offices to the core area, and enable default routes in each branch.
- D
Configure the branch offices as OSPF NSSAs (Not-So-Stubby Areas) and redistribute external routes into each area's OSPF database.
Show answer and explanation
Correct answer: A
Explanation
The correct answer is to configure branch offices as Totally Stubby Areas (TSAs) and enable area authentication. TSAs are ideal for branch offices because they prevent the propagation of external and inter-area routes into the branch areas, reducing resource consumption and improving scalability. Additionally, enabling OSPF authentication ensures secure routing, which is a critical requirement for enterprise networks.
- A. Correct.
Configuring the branch offices as OSPF Totally Stubby Areas (TSAs) prevents unnecessary OSPF updates by blocking external routes and inter-area routes, reducing resource consumption. Using OSPF authentication ensures secure routing.
- B. Incorrect.
A flat OSPF area design is not scalable and would burden the branch offices with all OSPF updates, which is not suitable for networks with resource-constrained devices.
- C. Incorrect.
Using OSPF virtual links unnecessarily complicates the design and does not address the issue of reducing OSPF updates for branch offices. Virtual links are typically used for connecting isolated areas to Area 0.
- D. Incorrect.
Configuring branch offices as NSSAs would still allow external routes to appear in the OSPF database, which might overwhelm branch resources and is not ideal for scalability.