The correct answer is to ensure the NLB is deployed in subnets that can route to the target subnets. This works because a Network Load Balancer operates at Layer 4 and does not require targets to be public; it simply needs a network path—via the VPC’s route tables—to the private subnet instances in each Availability Zone where those targets reside. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this concept tests your understanding that NLB traffic flows directly to the instance’s private IP, bypassing security groups for inbound rules, and that an Internet Gateway or NAT Gateway is unnecessary for internal routing. A common trap is assuming private targets need public exposure or a NAT device, but the NLB’s elastic network interface in your chosen subnets handles the routing. Memory tip: “NLB needs a lane, not a gate”—just ensure the load balancer’s subnet has a route to the target subnet’s CIDR.
SOA-C02 Networking and Content Delivery Practice Question
This SOA-C02 practice question tests your understanding of networking and content delivery. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a VPC with multiple subnets across two Availability Zones. The company wants to set up a Network Load Balancer (NLB) to handle TCP traffic to a fleet of EC2 instances. The instances are in private subnets. Which configuration is necessary to ensure the NLB can route traffic to the instances?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Ensure the NLB is deployed in subnets that can route to the target subnets
Option D is correct because NLB targets can be instances in private subnets as long as the NLB has a subnet in each AZ where targets reside. Option A is wrong because NLB does not require an internet gateway. Option B is wrong because security groups are not used for NLB traffic. Option C is wrong because NAT gateway is for outbound traffic.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Ensure the NLB is deployed in subnets that can route to the target subnets
Why this is correct
NLB must be in subnets that have routes to the target subnets; since targets are in private subnets, the NLB subnets must have appropriate routing.
Assign security groups to the NLB to allow inbound traffic
Why it's wrong here
NLB does not use security groups; it uses network ACLs.
✗
Configure a NAT gateway in each Availability Zone for the NLB to access the instances
Why it's wrong here
NLB communicates directly with targets within the VPC; NATgateway is not needed.
✗
Attach an internet gateway to the VPC and add a route to the NLB subnets
Why it's wrong here
NLB can be internet-facing or internal; an internet gateway is only needed if the NLB is internet-facing.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Networking and Content Delivery — This question tests Networking and Content Delivery — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Ensure the NLB is deployed in subnets that can route to the target subnets — Option D is correct because NLB targets can be instances in private subnets as long as the NLB has a subnet in each AZ where targets reside. Option A is wrong because NLB does not require an internet gateway. Option B is wrong because security groups are not used for NLB traffic. Option C is wrong because NAT gateway is for outbound traffic.
What should I do if I get this SOA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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