You’re planning to create a VPN connection to 2 VPCs in AWS. You are going to be using the same customer gateway in both cases. These VPCs have overlapping CIDR blocks. What can be done to ensure the routing is done right on the customer side?

Answer options:

A.Use static routes on the customer side.
B.Configure AS_PATH for each of the routes.
C.Use VRF technology for routing.
D.Use BFD technology for routing.

Answer – C
This is given in the AWS Documentation.
Virtual Routing and Forwarding (VRF) is a technology that allows multiple instances of a routing table to co-exist within the same router at the same time. Because the routing instances are independent, the same or overlapping IP addresses can be used without conflicting with each other. AWS recommends using VRFs when connecting a single customer gateway to multiple Amazon VPCs because the VPN connection creation logic is designed to ensure unique tunnel IP addresses for each connection within a single VPC, but not necessarily across multiple VPCs.
Options A and B are incorrect since these would not help in routing.
Option D is incorrect because this is used for failover connections.
For more information on configuring routes to multiple VPCs, please refer to the below URL
https://aws.amazon.com/articles/connecting-a-single-customer-router-to-multiple-vpcs/