- A
Enable sticky sessions (session affinity)
Why wrong: Does not help with failover.
- B
Configure health checks on the target group
Why wrong: Necessary but not sufficient for AZ failover.
- C
Add more subnets in additional AZs
Why wrong: Does not solve failover without cross-zone balancing.
- D
Enable cross-zone load balancing on the ALB
Allows traffic to be routed to healthy instances in any AZ.
Question 533 of 1,750
DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. 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 company uses an Application Load Balancer (ALB) to distribute traffic to EC2 instances. The ALB is in us-east-1a and us-east-1b. They want to ensure that if one AZ fails, traffic is routed only to healthy instances in the other AZ. What configuration is necessary?
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
✓
Enable cross-zone load balancing on the ALB
Cross-zone load balancing must be enabled on the ALB so that traffic can be distributed across instances in all AZs. By default, an ALB routes requests only to targets in the same Availability Zone as the requesting client. Enabling cross-zone load balancing allows the ALB to distribute traffic evenly across all registered targets in all enabled AZs, ensuring that if one AZ fails, traffic can be routed to healthy instances in other AZs. Option B is incorrect because health checks are already enabled by default and do not affect cross-AZ routing. Option C is incorrect because adding more AZs does not change the default AZ-affinity behavior; cross-zone load balancing must be explicitly enabled to utilize multiple AZs for failover.
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.
- ✗
Enable sticky sessions (session affinity)
Why it's wrong here
Does not help with failover.
- ✗
Configure health checks on the target group
Why it's wrong here
Necessary but not sufficient for AZ failover.
- ✗
Add more subnets in additional AZs
Why it's wrong here
Does not solve failover without cross-zone balancing.
- ✓
Enable cross-zone load balancing on the ALB
Why this is correct
Allows traffic to be routed to healthy instances in any AZ.
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
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.
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.
- →
Resilient Cloud Solutions — study guide chapter
Learn the concepts, then practise the questions
- →
Resilient Cloud Solutions practice questions
Targeted practice on this topic area only
- →
All DOP-C02 questions
1,750 questions across all exam domains
- →
AWS Certified DevOps Engineer Professional DOP-C02 study guide
Full concept coverage aligned to exam objectives
- →
DOP-C02 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related DOP-C02 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Configuration Management and IaC practice questions
Practise DOP-C02 questions linked to Configuration Management and IaC.
Resilient Cloud Solutions practice questions
Practise DOP-C02 questions linked to Resilient Cloud Solutions.
Monitoring and Logging practice questions
Practise DOP-C02 questions linked to Monitoring and Logging.
Incident and Event Response practice questions
Practise DOP-C02 questions linked to Incident and Event Response.
Security and Compliance practice questions
Practise DOP-C02 questions linked to Security and Compliance.
SDLC Automation practice questions
Practise DOP-C02 questions linked to SDLC Automation.
DOP-C02 fundamentals practice questions
Practise DOP-C02 questions linked to DOP-C02 fundamentals.
DOP-C02 scenario practice questions
Practise DOP-C02 questions linked to DOP-C02 scenario.
DOP-C02 troubleshooting practice questions
Practise DOP-C02 questions linked to DOP-C02 troubleshooting.
Practice this exam
Start a free DOP-C02 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this DOP-C02 question test?
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable cross-zone load balancing on the ALB — Cross-zone load balancing must be enabled on the ALB so that traffic can be distributed across instances in all AZs. By default, an ALB routes requests only to targets in the same Availability Zone as the requesting client. Enabling cross-zone load balancing allows the ALB to distribute traffic evenly across all registered targets in all enabled AZs, ensuring that if one AZ fails, traffic can be routed to healthy instances in other AZs. Option B is incorrect because health checks are already enabled by default and do not affect cross-AZ routing. Option C is incorrect because adding more AZs does not change the default AZ-affinity behavior; cross-zone load balancing must be explicitly enabled to utilize multiple AZs for failover.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More DOP-C02 practice questions
- A company uses AWS CodePipeline with a multi-branch strategy. A new feature branch triggers a pipeline that runs unit te…
- A development team uses AWS CodeBuild to compile a Java application and run unit tests. The build takes 30 minutes, but…
- A company uses AWS CodePipeline with multiple stages: Source (Amazon S3), Build (AWS CodeBuild), and Deploy (AWS CodeDep…
- A company uses AWS CodeCommit for source control. Developers frequently push large binary files (e.g., compiled JARs) to…
- A company runs a Stateful application on EC2 that requires sticky sessions. They use an ALB with duration-based stickine…
- An organization uses AWS CodePipeline to orchestrate deployments to multiple environments (dev, test, prod). Each enviro…
Last reviewed: Jun 20, 2026
This DOP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DOP-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.