The answer is that the subnet’s route table lacks a route to the internet gateway. For an EC2 instance to reach the internet, even with an Elastic IP attached, the subnet must have a default route (0.0.0.0/0) pointing to an internet gateway; without this route, traffic cannot leave the VPC. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of VPC routing fundamentals—a common trap is assuming an Elastic IP alone guarantees connectivity, when in fact the route table is the critical missing link. Remember the mnemonic: “EIP gives you a public address, but the route table gives you the path to the internet.”
SOA-C02 Deployment, Provisioning, and Automation Practice Question
This SOA-C02 practice question tests your understanding of deployment, provisioning, and automation. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 is using AWS CloudFormation to manage infrastructure. They have a stack that creates an EC2 instance and an Elastic IP. The instance is in a VPC with an internet gateway. The stack creation succeeds, but the instance does not have internet connectivity. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The subnet's route table does not have a route to the internet gateway.
Option A is correct because the instance must have a public IP to communicate with the internet; an Elastic IP attached to the instance provides that. Option B is wrong because the route table might not have a route to the internet gateway. Option C is wrong because the security group allows outbound traffic by default. Option D is wrong because the instance might be in a private subnet, but the question says VPC with IGW.
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.
✓
The subnet's route table does not have a route to the internet gateway.
Why this is correct
Without a route to the IGW, traffic cannot reach the internet.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The Elastic IP provides a public IP, so this is not the issue.
✗
The instance is in a private subnet.
Why it's wrong here
If it were in a private subnet, it would need a NATgateway; but the question states VPC with IGW.
✗
The security group does not allow outbound traffic.
Why it's wrong here
Security groups allow all outbound traffic by default.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The subnet's route table does not have a route to the internet gateway. — Option A is correct because the instance must have a public IP to communicate with the internet; an Elastic IP attached to the instance provides that. Option B is wrong because the route table might not have a route to the internet gateway. Option C is wrong because the security group allows outbound traffic by default. Option D is wrong because the instance might be in a private subnet, but the question says VPC with IGW.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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