Answer: Configure Bidirectional Forwarding Detection (BFD) on the Direct Connect connections on the on-premises router.

To reduce the BGP failover time from minutes to seconds, the most effective solution is to configure Bidirectional Forwarding Detection (BFD) on the Direct Connect connections. BFD is a protocol designed to detect faults in the bidirectional path between two forwarding engines, including interfaces, data links, and forwarding engines themselves, with very low overhead. It can provide sub-second failure detection times, which is significantly faster than the default BGP timers. While option A suggests reducing the BGP hold-down timer, this alone may not achieve the desired reduction in failover time without the rapid fault detection provided by BFD. Option B involves using Amazon CloudWatch and AWS Lambda for failover, which introduces additional complexity and may not achieve the sub-second failover times desired. Option C and D both suggest configuring BFD, but since the question asks for the solution that will provide the LARGEST reduction in BGP failover time, configuring BFD on the on-premises router (Option D) is the most direct and effective approach, as it ensures that the on-premises network can quickly detect and respond to failures on the Direct Connect connections.

Author: LeetQuiz Editorial Team