300-410 Question 151
Select 2A network engineer is tasked with configuring an enterprise network to ensure that specific traffic from a branch office to the data center takes a preferred path. Additionally, they need to prevent certain routes from being advertised to external peers. Which combination of policies should the engineer use to achieve this?
- A
Use route-maps for path manipulation and prefix-lists for filtering.
- B
Use BGP community attributes for path manipulation and distribute-lists for filtering.
- C
Use local preference for path manipulation and ACLs for filtering.
- D
Use AS path prepending for path manipulation and distribute-lists for filtering.
- E
Use MED for path manipulation and prefix-lists for filtering.
Show answer and explanation
Correct answers: A, D
Explanation
Path manipulation involves techniques like route-maps and AS path prepending to influence the preferred route for traffic. Filtering, on the other hand, ensures that specific routes are advertised or blocked as needed, typically using tools like prefix-lists or distribute-lists. Combining route-maps or AS path prepending with appropriate filtering tools ensures precise control over routing behavior.
- A. Correct.
Correct. Route-maps can be used to manipulate path selection in various routing protocols by setting attributes like local preference or MED, and prefix-lists are effective for filtering specific routes.
- B. Incorrect.
Incorrect. While BGP communities can influence routing decisions, they are not used directly for path manipulation. Distribute-lists can filter routes but are less flexible compared to prefix-lists in some scenarios.
- C. Incorrect.
Incorrect. Local preference is effective for influencing path selection, but ACLs are generally used for packet filtering, not route filtering.
- D. Correct.
Correct. AS path prepending is a common technique for influencing the path selection in BGP, and distribute-lists are valid for filtering routes.
- E. Incorrect.
Incorrect. While MED can influence path selection in BGP between different autonomous systems, prefix-lists are better suited for route filtering rather than manipulation.