AWS Certified Advanced Networking – Specialty ANS-C00 – Question246

Your company just acquired a new company. You have two VPCs ?one is 172.31.0.0/16 and one is 10.111.0.0/16. The acquired company uses 10.111.0.0/16 for their VPC. Your VPC "A" has a group of 12 servers in the range 10.111.2.101 ?10.111.2.112. Their VPC "B" has 20 servers from 10.111.2.171 ? 10.111.2.190. You need to access both VPCs from the 172.31.0.0/16 VPC "C".
What is the best way to approach this problem?

A. From VPC C, create a peering connection and add a route to VPC A's peering connection for 10.111.2.96/27 and a route to VPC B's peering connection for 10.111.2.0/24.
B. From VPC C, create a peering connection and add a route to VPC A's peering connection for 10.111.2.96/28 and a route to VPC B's peering connection for 10.111.2.0/24.
C. From VPC C, create a peering connection and adjust the route tables to direct traffic to the individual servers by exact IP address of the servers.
D. Invest the money and change the CIDR of one of the VPCs since one VPC cannot be peered to two VPCs with the same CIDR block.

Correct Answer: A

Explanation:

Explanation:
You can peer VPCs with the same CIDR block to a third VPC, so changing the CIDR block is not necessary. You can adjust the route tables to point to individual servers, but this would be very inefficient. 10.111.2.96/28 does not provide enough addresses for the AWS required addresses. AWS reserves 5 addresses per subnet and this only allows 11 addresses. 10.111.2.96/27 provides 32 addresses with 27 usable. Since it is a /27, it will take precedence over the /24 and route the traffic destined for these instances correctly.