AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 143

A company has critical VPC workloads that connect to an on-premises data center through two redundant active-passive AWS Direct Connect connections. However, a recent outage on one Direct Connect connection revealed that it takes more than a minute for traffic to fail over to the secondary Direct Connect connection. The company wants to reduce the failover time from minutes to seconds.

Which solution will provide the LARGEST reduction in the BGP failover time?

Answer options

• A. Reduce the BGP hold-down timer that is configured on the BGP sessions on the Direct Connect connection VIFs.
• B. Configure an Amazon CloudWatch alarm for the Direct Connect connection state to invoke an AWS Lambda function to fail over the traffic.
• C. Configure Bidirectional Forwarding Detection (BFD) on the Direct Connect connections on the AWS side.
• D. Configure Bidirectional Forwarding Detection (BFD) on the Direct Connect connections on the on-premises router.

Correct answer: D

Explanation

Configuring Bidirectional Forwarding Detection (BFD) on the on-premises router (option D) significantly reduces the failover time by allowing faster detection of link failures compared to relying solely on BGP timers. Options A and C may help but do not provide the same level of rapid detection as BFD. Option B introduces additional complexity and does not directly address the failover time issue.