SAP-C02 · Question #560
SAP-C02 Question #560: Real Exam Question with Answer & Explanation
The correct answer is A: Update the Auto Scaling group to use the AZ2 subnet only. Delete and re-create the AZ1 subnet. To incorporate a new Availability Zone into a VPC without downtime or adding IP space, existing subnets must be re-sized by temporarily shifting Auto Scaling group traffic to one AZ, re-creating a subnet with a smaller CIDR, and then creating a new subnet in the new AZ, ensuring
Question
A solutions architect has an operational workload deployed on Amazon EC2 instances in an Auto Scaling group. The VPC architecture spans two Availability Zones (AZ) with a subnet in each that the Auto Scaling group is targeting. The VPC is connected to an on-premises environment and connectivity cannot be interrupted. The maximum size of the Auto Scaling group is 20 instances in service. The VPC IPv4 addressing is as follows: VPC CIDR: 10.0.0.0/23 AZ1 subnet CIDR: 10.0.0.0/24 AZ2 subnet CIDR: 10.0.1.0/24 Since deployment, a third AZ has become available in the Region. The solutions architect wants to adopt the new AZ without adding additional IPv4 address space and without service downtime. Which solution will meet these requirements?
Options
- AUpdate the Auto Scaling group to use the AZ2 subnet only. Delete and re-create the AZ1 subnet
- BTerminate the EC2 instances in the AZ1 subnet. Delete and re-create the AZ1 subnet using half
- CCreate a new VPC with the same IPv4 address space and define three subnets, with one for each
- DUpdate the Auto Scaling group to use the AZ2 subnet only. Update the AZ1 subnet to have half
Explanation
To incorporate a new Availability Zone into a VPC without downtime or adding IP space, existing subnets must be re-sized by temporarily shifting Auto Scaling group traffic to one AZ, re-creating a subnet with a smaller CIDR, and then creating a new subnet in the new AZ, ensuring continuous service.
Common mistakes.
- B. Terminating instances in AZ1 before re-creating the subnet can lead to service downtime if the Auto Scaling group cannot immediately scale up in AZ2 to compensate for the lost capacity.
- C. Creating a new VPC with the same IP address space would require re-establishing the on-premises connectivity, leading to significant downtime and configuration changes, which violates the requirement of no service downtime.
- D. Subnets cannot be updated to have a different CIDR range after creation; they must be deleted and re-created if the CIDR needs to change.
Concept tested. VPC subnet management, Auto Scaling group, zero-downtime AZ expansion
Reference. https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html
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