350-401 Question 479
Single answerYou are troubleshooting connectivity issues in a multi-path BGP environment. One of your routers, R1, is receiving multiple BGP routes for the same destination network from different neighbors. The router is not selecting the expected path as the best path. Upon further investigation, you notice that the paths have the same weight and local preference, but differ in other attributes. Which BGP attribute will the router evaluate next to determine the best path?
- A
AS_PATH
- B
MED (Multi-Exit Discriminator)
- C
Origin Code
- D
IGP Metric to Next Hop
Show answer and explanation
Correct answer: A
Explanation
BGP uses a strict path-selection algorithm to determine the best path. After weight and local preference, the AS_PATH attribute is evaluated to choose the path with the shortest AS_PATH length. This ensures that the router selects the path that traverses the least number of autonomous systems.
- A. Correct.
Correct. After weight and local preference, BGP evaluates the AS_PATH attribute to determine the best path. The path with the shortest AS_PATH is preferred.
- B. Incorrect.
Incorrect. MED (Multi-Exit Discriminator) is evaluated after comparing AS_PATH and Origin Code. It is used when multiple paths are from the same AS.
- C. Incorrect.
Incorrect. Origin Code is considered after AS_PATH, but it is not the next attribute evaluated in this scenario.
- D. Incorrect.
Incorrect. IGP Metric to Next Hop is evaluated much later in the BGP best-path selection process, after other key attributes like MED.