SAP-C02 Q624 · Networking

Question

A solutions architect has created a single VPC on AWS. The VPC has one internet gateway and one NAT gateway. The VPC extends across three Availability Zones. Each Availability Zone includes one public subnet and one private subnet. The three private subnets contain Amazon EC2 instances that must be able to connect to the internet. Which solution will increase the network resiliency of this architecture?

Accepted Answer

**Answer A** is correct because it addresses every requirement:

1. **Current problem**: There is only ONE NAT gateway serving all three Availability Zones. If the AZ hosting that NAT gateway goes down, EC2 instances in the other two private subnets lose internet connectivity. This is a **single point of failure**.

2. **Solution — One NAT gateway per AZ**: By adding two more NAT gateways (total of three, one in each AZ's public subnet), you eliminate the cross-AZ dependency. Each AZ becomes self-contained for outbound internet traffic.

3. **Route table configuration**: Each private subnet's route table is updated to point `0.0.0.0/0` to the NAT gateway **in the same Availability Zone**. This ensures:
   - **Resiliency**: If one AZ fails, only instances in that AZ are affected. Instances

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