The answer is to update the /etc/hosts file with the new private IP addresses or assign Elastic IPs to preserve them. This is correct because when EC2 instances in a cluster placement group are stopped and started, their private IP addresses can change unless they are attached to a primary Elastic Network Interface or an Elastic IP. Since SAP HANA scale-out configurations rely on hostnames resolved via /etc/hosts for inter-node communication, the old IPs become stale after the restart, breaking the cluster. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of how stop/start behavior affects private IPs in placement groups and the critical role of static hostname resolution in HANA topologies. A common trap is assuming placement groups preserve IPs—they only ensure low latency, not address persistence. Memory tip: “Stop and start? IPs depart—update hosts or use EIPs to keep them smart.”
PAS-C01 Design of SAP Workloads on AWS Practice Question
This PAS-C01 practice question tests your understanding of design of sap workloads on aws. 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 organization has a production SAP ERP system on AWS with a multi-node SAP HANA scale-out configuration. The system uses a cluster placement group for low latency. During a maintenance window, the administrator needs to stop and start all instances. After restart, the HANA nodes cannot communicate with each other. The cluster placement group is still intact, but the private IP addresses have changed. The HANA topology relies on hostnames resolved via /etc/hosts. What is the MOST likely cause and solution?
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 private IP addresses changed, but /etc/hosts still has the old IPs. Update /etc/hosts with the new IPs or use Elastic IPs.
When EC2 instances in a cluster placement group are stopped and started, the private IP addresses can change unless they are configured with a primary Elastic Network Interface (ENI) or Elastic IP. Since the SAP HANA scale-out topology relies on hostnames resolved via /etc/hosts, the old IPs in that file become stale after the restart, breaking inter-node communication. Updating /etc/hosts with the new private IPs or assigning Elastic IPs to preserve the addresses resolves the issue.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 private IP addresses changed, but /etc/hosts still has the old IPs. Update /etc/hosts with the new IPs or use Elastic IPs.
Why this is correct
Stop/start can change private IPs; using Elastic IPs or updating /etc/hosts resolves this.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The EBS volumes were detached during stop. Reattach the volumes.
Why it's wrong here
EBS volumes remain attached across stop/start.
✗
The security group rules were reset. Reapply the security group rules.
Why it's wrong here
Security groups persist across stop/start.
✗
The cluster placement group was removed during stop/start. Recreate the placement group.
Why it's wrong here
Placement groups persist across stop/start if not explicitly deleted.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume stopping and starting instances preserves all network configurations, but AWS explicitly changes private IPs by default unless Elastic IPs or static ENIs are used, which is a key nuance for SAP HANA multi-node setups.
Detailed technical explanation
How to think about this question
By default, EC2 instances in a VPC receive a new private IP address from the subnet’s CIDR range when stopped and started, unless an Elastic IP or secondary ENI is attached. SAP HANA scale-out systems use internal hostname resolution (often via /etc/hosts) for node discovery and communication; if IPs change without updating this file, the HANA cluster fails to form. Using Elastic IPs or primary ENIs with static private IPs ensures address persistence across stop/start cycles, which is a common best practice for SAP on AWS.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design of SAP Workloads on AWS — This question tests Design of SAP Workloads on AWS — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The private IP addresses changed, but /etc/hosts still has the old IPs. Update /etc/hosts with the new IPs or use Elastic IPs. — When EC2 instances in a cluster placement group are stopped and started, the private IP addresses can change unless they are configured with a primary Elastic Network Interface (ENI) or Elastic IP. Since the SAP HANA scale-out topology relies on hostnames resolved via /etc/hosts, the old IPs in that file become stale after the restart, breaking inter-node communication. Updating /etc/hosts with the new private IPs or assigning Elastic IPs to preserve the addresses resolves the issue.
What should I do if I get this PAS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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