300-420 Question 33
Single answerYou are designing a network for a global enterprise with multiple branch offices. The network uses BGP for routing between sites. The company requires traffic from a specific branch office to always prefer a primary data center unless the link to that data center fails. Which BGP attribute should you configure to enforce this path preference?
- A
Local Preference
- B
AS Path Prepending
- C
MED (Multi-Exit Discriminator)
- D
Weight
Show answer and explanation
Correct answer: D
Explanation
The Weight attribute is a Cisco-specific BGP path attribute that is local to the router and not advertised to other routers. It is used to influence the router's decision about which path to prefer. In this scenario, configuring a higher Weight for the route to the primary data center ensures that traffic from the branch office uses that path as the default. If the link to the primary data center fails, BGP will automatically failover to the secondary path.
- A. Incorrect.
Local Preference is used to influence outbound traffic within an autonomous system. It is not typically used to enforce path preference from a specific branch office to a data center.
- B. Incorrect.
AS Path Prepending is used to make a path less preferred by adding artificial AS numbers to the AS path. This is not the best choice to enforce a primary path preference.
- C. Incorrect.
MED (Multi-Exit Discriminator) is used to influence path selection between two autonomous systems, but it is not the most suitable attribute for preferring a primary data center from a specific branch office.
- D. Correct.
Weight is a Cisco-specific attribute that is used to influence the local router's path preference. It is the most appropriate choice in this scenario to ensure that traffic from the branch office prefers the primary data center.