Q42 — AWS ANS-C01 Ch.1

Question 42 of 100 | ← Chapter 1

A logistics company has multiple VPCs in an AWS Region. The company uses a transit gateway to connect the VPCs. The company has several On-premises offices that connect to the transit gateway by using AWS Site-to-Site VPN connections over the internet. The company has configured One transit gateway VPN attachment for each office. Route propagation is enabled on all route tables. Each Site-to-Site VPN connection uses two tunnels in an active-passive configuration. The Company configured each office with appropriate static routes on both the Site-to-Site VPN connection and the office’s customer gateway. The company wants to use both IPsec tunnels of every office to maximize the overall VPN connection bandwidth. Which design changes are necessary to meet these requirements?

• A. Create an AWS Transit Gateway Connect attachment for each office Use the existing VPN attachments as the transport for the new Connect Attachments. Set up a Generic Routing Encapsulation (GRE) tunnel on each customer gateway that terminates on the Connect attachment for each office. Move the static routes From the transit gateway VPN attachment to the customer gateway for the transit gateway Connect attachment.
• B. Enable equal-cost multi-path (ECMP) routing on the transit gateway. Ensure ECMP is supported by and enabled on the customer gateways. Enable ECMP on the Site-to-Site VPN connection. Ensure static routes on the customer gateways have equal metrics and administrative Distance.
• C. Enable equal-cost multi-path (ECMP) routing on the transit gateway. (Ensure ECMP is supported by and enabled on the customer gateways. Change the routing configuration between the transit gateway and the customer gateways from static routing to BGP. Remove related static Routes from the customer gateways. ✓
• D. Enable equal-cost multi-path (ECMP) routing on the transit gateway. Ensure ECMP is supported by and enabled on the customer gateways. Change the routing configuration between the transit gateway and the customer gateways from static routing to BGP. Ensure the customer Gateway applies the correct community strings to give the transit gateway the ability to perform ECMP forwarding.

Correct Answer: C. Enable equal-cost multi-path (ECMP) routing on the transit gateway. (Ensure ECMP is supported by and enabled on the customer gateways. Change the routing configuration between the transit gateway and the customer gateways from static routing to BGP. Remove related static Routes from the customer gateways.

Explanation

AWS Transit Gateway支持ECMP（等价多路径路由）时要求使用动态路由协议BGP，而非静态路由。静态路由无法实现多路径负载均衡。启用ECMP需确保客户网关支持并配置BGP，替换原有的静态路由。AWS官方文档指出，Transit Gateway通过BGP动态路由协议才能利用多个VPN隧道实现带宽聚合。选项C正确地将静态路由转为BGP，移除了静态路由的约束，符合ECMP的运行条件。其他选项要么保留静态路由（B），要么引入不必要的社区字符串配置（D），或采用非标准技术（A）。