The answer is enabling DNS resolution for the VPC peering connection. This is required because VPC peering does not automatically propagate DNS hostnames between the peered VPCs, so the SAP application servers cannot resolve the HANA database’s private DNS name to its private IP address. Without this setting, the application servers may attempt to reach the database via a public IP or fail entirely, even though security groups and routes are correctly configured. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of how VPC peering interacts with DNS resolution, a common trap where candidates focus on security groups or NACLs instead of the underlying name resolution issue. Remember that VPC peering is a simple layer-3 connection—DNS does not cross it unless you explicitly enable both DNS resolution and DNS hostnames in the peering options. A useful memory tip: “Peering connects the network, but DNS needs a handshake across the link.”
PAS-C01 Operations and Maintenance Practice Question
This PAS-C01 practice question tests your understanding of operations and maintenance. 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.
An SAP administrator is troubleshooting an issue where SAP application servers are unable to connect to the SAP HANA database. The database is running on an EC2 instance in a private subnet. The application servers are in a different VPC connected via VPC peering. The security group for the database instance allows TCP port 3$15$13 from the application server security group. Which additional configuration is MOST likely required?
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
✓
Enable DNS resolution for the VPC peering connection.
Option C is correct because VPC peering does not automatically resolve DNS hostnames between VPCs. The application servers must resolve the database hostname to the private IP of the database instance. Option A is wrong because VPC peering does not support transitive routing, but that's not relevant here. Option B is wrong because NACLs are stateless and must allow return traffic, but the issue is DNS resolution. Option D is wrong because the security group rule already allows the port.
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.
✗
Modify the security group to allow traffic from the application server subnet CIDR.
Why it's wrong here
The security group already allows traffic from the application server security group.
✗
Update the route tables to add a route to the database subnet.
Why it's wrong here
Route tables are needed for connectivity, but the symptom is DNS resolution failure.
✗
Add a rule to the network ACL to allow inbound traffic on port 3$15$13.
Why it's wrong here
NACLs are stateless, but the issue is DNS resolution, not network ACLs.
✓
Enable DNS resolution for the VPC peering connection.
Why this is correct
VPC peering requires DNS resolution to be enabled for hostname resolution across VPCs.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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 PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Operations and Maintenance — This question tests Operations and Maintenance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable DNS resolution for the VPC peering connection. — Option C is correct because VPC peering does not automatically resolve DNS hostnames between VPCs. The application servers must resolve the database hostname to the private IP of the database instance. Option A is wrong because VPC peering does not support transitive routing, but that's not relevant here. Option B is wrong because NACLs are stateless and must allow return traffic, but the issue is DNS resolution. Option D is wrong because the security group rule already allows the port.
What should I do if I get this PAS-C01 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 PAS-C01 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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