Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A SysOps administrator is troubleshooting connectivity issues between Amazon EC2 instances in two different VPCs that are connected via a VPC peering connection. The instances can successfully send ICMP (ping) traffic, but TCP connections on port 443 (HTTPS) fail. The security groups of both instances allow all inbound and outbound traffic. What is the most likely cause of the issue?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
The Network ACL associated with the subnets is blocking the return traffic for TCP connections on ephemeral ports
NACLs are stateless; they require explicit inbound and outbound rules. ICMP may be allowed, but TCP return traffic is blocked if ephemeral ports are not allowed in the outbound NACL.
B
Distractor review
The VPC peering connection is not properly configured for TCP traffic
VPC peering connections do not filter traffic by protocol; they connect the VPCs and rely on route tables and security groups for filtering.
C
Distractor review
The route tables in the VPCs do not contain a route for the other VPC's CIDR
If route tables were missing, ICMP would also fail because ICMP requires routing just like TCP.
D
Distractor review
The security group on the EC2 instance is blocking inbound TCP traffic on port 443
The question states that security groups allow all inbound and outbound traffic, so this cannot be the cause.
Common exam trap
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.
Technical deep dive
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.
Related practice questions
Related SOA-C02 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A company uses Amazon CloudFront to deliver content to a global audience. The origin is an Application Load Balancer in us-east-1. The SysOps administrator wants to reduce costs by minimizing the number of requests that reach the origin server. Which action should the administrator take?
Question 2
A company runs a batch processing application on Amazon EC2 that runs for 2 hours every night. The workload can tolerate interruptions. Which EC2 purchasing option provides the lowest cost for this use case?
Question 3
A SysOps administrator needs to monitor the CPU utilization of an Amazon RDS DB instance and receive an alarm when CPU utilization exceeds 80% for 5 consecutive minutes. Which AWS service should be used to create this alarm?
Question 4
A company runs a critical web application on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer (ALB). The application uses session stickiness (sticky sessions) to maintain user sessions. The SysOps administrator notices that when instances are replaced during a scale-in or failure event, users lose their session data. The administrator needs to preserve session data across instance failures without losing stickiness benefits. What should the administrator do?
Question 5
A company runs a production web application on a single Amazon EC2 instance. The application experiences a predictable and steady workload 24/7. The SysOps administrator wants to minimize compute costs for this instance while ensuring it remains available during the expected workload. Which EC2 purchasing option should the administrator use?
Question 6
A company has a VPC with public and private subnets. The private subnets host application servers that need to make outbound HTTPS connections to the internet. The SysOps administrator must implement a solution that provides outbound internet connectivity while preventing inbound connections from the internet. Additionally, the solution must allow the company to control which domains the application servers can access. Which solution should the administrator implement?
FAQ
Questions learners often ask
What does this SOA-C02 question test?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: The Network ACL associated with the subnets is blocking the return traffic for TCP connections on ephemeral ports — Network Access Control Lists (NACLs) are stateless, meaning they filter traffic based on both inbound and outbound rules. ICMP may be allowed by NACL rules (e.g., allowing all ICMP), but TCP traffic may require explicit outbound rules for ephemeral ports to allow return traffic. Since security groups are stateful and allow return traffic automatically, the failure points to NACLs as the cause. Route tables do not differentiate traffic types; peering connections allow all traffic unless filtered.
What should I do if I get this SOA-C02 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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