- A
The NAT gateway is in the same subnet as the instance
Why wrong: NAT gateway is in a public subnet.
- B
The route table of the private subnet has a route to the NAT gateway
Required for traffic to reach NAT gateway.
- C
The internet gateway is attached to the private subnet
Why wrong: IGW is attached to VPC, not subnet.
- D
The instance has a public IP address
Why wrong: Private instances use NAT, not public IP.
- E
The security group allows outbound traffic to the internet
Security group must allow outbound traffic.
Question 1,253 of 1,750
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 DevOps engineer is troubleshooting an issue where an EC2 instance in a private subnet cannot reach the internet. The instance has a route to a NAT gateway. Which TWO of the following should the engineer check? (Choose TWO.)
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
✓
The route table of the private subnet has a route to the NAT gateway
Option B is correct because the private subnet's route table must have a route pointing to the NAT gateway for traffic to be forwarded to the internet. Option E is correct because the security group associated with the EC2 instance must allow outbound traffic (e.g., HTTPS) to reach the internet; otherwise, packets are dropped. Option A is incorrect because the NAT gateway must be in a public subnet, not the same private subnet as the instance. Option C is incorrect because the internet gateway is attached to the VPC, not to the subnet directly; private subnets use NAT to access the internet. Option D is incorrect because instances in private subnets do not require public IP addresses; they use the NAT gateway's public IP.
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 NAT gateway is in the same subnet as the instance
- ✓
The route table of the private subnet has a route to the NAT gateway
- ✗
The internet gateway is attached to the private subnet
Why it's wrong here
IGW is attached to VPC, not subnet.
- ✗
The instance has a public IP address
Why it's wrong here
Private instances use NAT, not public IP.
- ✓
The security group allows outbound traffic to the internet
Why this is correct
Security group must allow outbound traffic.
Related concept
CIDR notation defines the prefix length.
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.
Visual reference
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 DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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Incident and Event Response — study guide chapter
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Incident and Event Response — This question tests Incident and Event Response — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The route table of the private subnet has a route to the NAT gateway — Option B is correct because the private subnet's route table must have a route pointing to the NAT gateway for traffic to be forwarded to the internet. Option E is correct because the security group associated with the EC2 instance must allow outbound traffic (e.g., HTTPS) to reach the internet; otherwise, packets are dropped. Option A is incorrect because the NAT gateway must be in a public subnet, not the same private subnet as the instance. Option C is incorrect because the internet gateway is attached to the VPC, not to the subnet directly; private subnets use NAT to access the internet. Option D is incorrect because instances in private subnets do not require public IP addresses; they use the NAT gateway's public IP.
What should I do if I get this DOP-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 DOP-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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Last reviewed: Jun 20, 2026
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