Answer – B and C
The AWS Documentation mentions this use case and how the routes should be configured.
· More specific routes: With this approach, both Customer Gateway 1 and Customer Gateway 2 advertise a summary route of 10.0.0.0/15. In addition, Customer Gateway 1 advertises 10.0.0.0/16 and Customer Gateway 2 advertises 10.1.0.0/16. AWS will use the more specific routes to send traffic to the appropriate data center and fail back to the other data center following the summarized route if the more specific route becomes temporarily unavailable.
· AS-path prepending: With this approach, both Customer Gateway 1 and Customer Gateway 2 advertise 10.0.0.0/16 and 10.1.0.0/16. However, Customer Gateway 1 uses AS-path prepending when advertising the 10.1.0.0/16 network to make this route less preferred. Likewise, Customer Gateway 2 uses AS-path prepending when advertising the 10.0.0.0/16 network to make this route less preferred. AWS will use the preferred routes to send traffic to the appropriate data center and will fail back to the other data center following the less preferred routes when necessary.
Option A is incorrect because you should use dynamic routes.
Option D is incorrect because we already have 2 VPN connections.
For more information on Datacenter high availability, please visit the below URL:
https://aws.amazon.com/answers/networking/aws-multiple-data-center-ha-network-connectivity/