Q71 — AWS ANS-C01 Ch.1

Question 71 of 100 | ← Chapter 1

A network engineer configures a second AWS Direct Connect connection to an existing network. The network engineer runs a test in the AWS Direct Connect Resiliency Toolkit on the connections. The test produces a failure. During the failover event, the network engineer observes a 90- Second interruption before traffic shifts to the failover connection. Which solution will reduce the time for failover?

• A. Decrease the BGP hello timer to 5 seconds.
• B. Add a VPN connection to the connectivity solution. Implement fast failover.
• C. Configure Bidirectional Forwarding Detection (BFD) on the on-premises router. ✓
• D. Decrease the BGP hold-down timer to 5 seconds.

Correct Answer: C. Configure Bidirectional Forwarding Detection (BFD) on the on-premises router.

Explanation

AWS Direct Connect Resiliency Toolkit测试中出现故障转移时延问题。AWS Direct Connect文档指出，BGP收敛速度通常受制于默认计时器，传统BGP检测故障可能需要分钟级。配置Bidirectional Forwarding Detection（BFD）能在毫秒级检测链路故障，加快BGP会话的中断感知。选项A/BGP hello计时器调整无法显著降低检测延迟，选项D的BGP保持计时器实际无法单独设置为5秒（标准值为3倍hello时间），选项B的VPN并非Direct Connect场景推荐方案。正确答案C通过BFD实现亚秒级故障检测，符合AWS架构最佳实践。