The answer is to enable cross-zone load balancing on the Application Load Balancer. This feature ensures that traffic is distributed evenly across all healthy targets in every enabled Availability Zone, rather than being restricted to targets within the same zone as the receiving ALB node. By doing so, it prevents a scenario where a surge of requests to one zone overwhelms its local instances while other zones remain underutilized, allowing the application to absorb sudden traffic spikes without manual scaling. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of how ALB nodes map to AZs and the default behavior of distributing traffic only within a node’s zone—a common trap is assuming the ALB automatically balances across zones. Remember the mnemonic “Cross for Even” to recall that cross-zone load balancing creates even distribution across all AZs, which is essential for high availability.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 solutions architect needs to design a highly available web application that uses an Application Load Balancer (ALB) and spans multiple Availability Zones (AZs) in a single region. The application must be able to handle a sudden increase in traffic without manual intervention. Which feature should the architect enable on the ALB to meet this requirement?
Why wrong: Connection draining ensures existing connections complete before deregistration, but does not help with traffic spikes.
B
Enable sticky sessions
Why wrong: Sticky sessions bind a user's session to a specific target, but do not help distribute traffic spikes evenly.
C
Enable cross-zone load balancing
Cross-zone load balancing distributes traffic evenly across instances in all AZs, allowing the ALB to handle spikes by using all healthy instances effectively.
D
Enable deletion protection
Why wrong: Deletion protection prevents the ALB from being deleted accidentally; it does not affect traffic handling.
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
Cross-zone load balancing distributes incoming traffic evenly across all registered targets in all enabled Availability Zones, rather than sending traffic only to targets in the same AZ as the load balancer node. This ensures that if one AZ receives more traffic than another, the ALB can still balance the load across all healthy instances, allowing the application to handle sudden traffic spikes without manual scaling intervention.
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.
✗
Enable connection draining
Why it's wrong here
Connection draining ensures existing connections complete before deregistration, but does not help with traffic spikes.
✗
Enable sticky sessions
Why it's wrong here
Sticky sessions bind a user's session to a specific target, but do not help distribute traffic spikes evenly.
✓
Enable cross-zone load balancing
Why this is correct
Cross-zone load balancing distributes traffic evenly across instances in all AZs, allowing the ALB to handle spikes by using all healthy instances effectively.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable deletion protection
Why it's wrong here
Deletion protection prevents the ALB from being deleted accidentally; it does not affect traffic handling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse cross-zone load balancing with auto scaling, but cross-zone load balancing is a feature of the ALB itself that distributes existing traffic more evenly, whereas auto scaling handles capacity changes; the question specifically asks for a feature to handle sudden traffic increase without manual intervention, and cross-zone load balancing ensures the ALB can use all available capacity across AZs immediately.
Detailed technical explanation
How to think about this question
By default, ALB nodes are created in each enabled AZ and only route requests to targets within that same AZ. Enabling cross-zone load balancing overrides this behavior, allowing each ALB node to distribute traffic to targets across all AZs. This is particularly important in scenarios where client traffic is unevenly distributed across AZs (e.g., due to DNS resolver behavior), as it prevents one AZ from being overloaded while others remain underutilized.
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.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable cross-zone load balancing — Cross-zone load balancing distributes incoming traffic evenly across all registered targets in all enabled Availability Zones, rather than sending traffic only to targets in the same AZ as the load balancer node. This ensures that if one AZ receives more traffic than another, the ALB can still balance the load across all healthy instances, allowing the application to handle sudden traffic spikes without manual scaling intervention.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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