300-420 Question 11
Select 3A financial organization is deploying IS-IS as its Interior Gateway Protocol (IGP) across its enterprise network. The network design must ensure scalability, stability, and security. Which of the following design considerations should be implemented to meet these requirements?
- A
Use hierarchical routing with multiple IS-IS levels to contain route updates and minimize flooding.
- B
Enable IS-IS authentication between neighboring routers to protect against unauthorized routing updates.
- C
Configure a flat single-level IS-IS area to simplify the routing topology and reduce configuration complexity.
- D
Deploy route summarization between IS-IS level boundaries to reduce the size of the routing table.
- E
Use metrics to assign equal weights to all links to ensure consistent path selection across the network.
Show answer and explanation
Correct answers: A, B, D
Explanation
Scalable, secure, and stable IS-IS routing designs require the use of hierarchical routing with IS-IS levels, authentication for security, and route summarization to minimize routing table size and improve network performance. Flat IS-IS topologies and equal link metrics are not suited for large-scale or complex networks.
- A. Correct.
Using hierarchical routing with multiple IS-IS levels (Level 1 and Level 2) limits the scope of flooding for route updates, improving scalability and stability. This is a best practice for scalable routing designs.
- B. Correct.
Enabling IS-IS authentication ensures that only authorized routers can exchange routing information, enhancing the security of the routing design.
- C. Incorrect.
A flat single-level IS-IS area is not scalable for large networks, as it can lead to excessive flooding and instability. It is more suitable for small, simple networks.
- D. Correct.
Route summarization reduces the size of the routing table and limits the propagation of detailed routes across IS-IS level boundaries, enhancing scalability and stability.
- E. Incorrect.
Assigning equal weights to all links is not a recommended practice as it does not account for varying link capacities or performance. Proper metric tuning is necessary to optimize path selection.