350-401 Question 462
Single answerA network engineer is configuring a multi-homed BGP environment for an enterprise network connected to two ISPs. The engineer wants to ensure that outbound traffic primarily uses ISP1 unless ISP1 becomes unavailable, in which case ISP2 should be used. Which BGP attribute should the engineer modify to influence the path preference in this scenario?
- A
Local Preference
- B
AS Path Prepending
- C
Multi-Exit Discriminator (MED)
- D
Weight
Show answer and explanation
Correct answer: D
Explanation
In this scenario, the network engineer needs to influence the outbound path preference in a multi-homed BGP setup. The Weight attribute is the best choice because it is a local attribute specific to a router and can be configured to prioritize ISP1 for outbound traffic. In contrast, Local Preference is used within the same AS, AS Path Prepending is suited for inbound traffic manipulation, and MED is irrelevant for outbound path selection.
- A. Incorrect.
Local Preference is used to influence the BGP path selection for outbound traffic within the same Autonomous System (AS). However, it is not exchanged between different ASes, making it unsuitable for this multi-homed ISP scenario.
- B. Incorrect.
AS Path Prepending is typically used to influence inbound traffic by making a path appear less desirable to other ASes. It does not directly control outbound path preference.
- C. Incorrect.
Multi-Exit Discriminator (MED) is used to influence inbound traffic between two connected ASes. It is not applicable for controlling outbound traffic preference in this scenario.
- D. Correct.
Weight is a Cisco-proprietary attribute used to influence outbound path preference on a local router. It is not shared with other routers, making it an ideal choice for this scenario where outbound traffic preference needs to be set.