SAP-C02 Continuous Improvement for Existing Solutions Practice Question
A company runs a critical workload on EC2 instances in an Auto Scaling group across three Availability Zones. The application needs to maintain a consistent IP address for outbound traffic to external partners. The current design uses a NAT gateway in each AZ, but partners whitelist a single IP. How can the company provide a fixed outbound IP while maintaining high availability?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy a Network Load Balancer with Elastic IPs in front of NAT instances in each AZ.
A Network Load Balancer (NLB) with Elastic IPs can distribute traffic to NAT instances across multiple Availability Zones, providing a fixed outbound IP and high availability. If one AZ fails, the NLB redirects traffic to healthy NAT instances in other AZs, ensuring the workload remains operational. Option A is incorrect because a proxy fleet behind an ALB would still result in multiple outbound IPs, as ALB instances have different IPs. Option B is incorrect because using a single NAT gateway across all AZs is not possible – NAT gateways are AZ-specific and cannot span zones; also, a single NAT gateway is a single point of failure. Option C is incorrect because a single NAT instance in one AZ lacks high availability – if that AZ fails, outbound connectivity is lost.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a proxy fleet of EC2 instances behind an Application Load Balancer.
Why it's wrong here
ALB does not provide a single static outbound IP.
- ✗
Use a single NAT gateway across all three AZs and assign an Elastic IP.
Why it's wrong here
A NAT gateway is AZ-resilient only within its zone; cross-AZ routing is not supported.
- ✗
Use a NAT instance with an Elastic IP in one AZ.
Why it's wrong here
Single point of failure.
- ✓
Deploy a Network Load Balancer with Elastic IPs in front of NAT instances in each AZ.
Why this is correct
NLB provides a static IP and distributes traffic to NAT instances across AZs for HA.
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Written by Johnson Ajibi, MSc IT Security
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