ANS-C01 Network Design Practice Question
A company is designing a network for a critical application that requires high availability across three Availability Zones in a single AWS Region. The application uses Network Load Balancers (NLBs) and Application Load Balancers (ALBs). The company must ensure that cross-zone load balancing is enabled for the NLBs and that the ALBs have a fixed response timeout. Which combination of settings meets these requirements?
⚠ Common exam trap
Watch out — candidates often confuse the cross-zone load balancing capability of NLBs (which can be toggled) with ALBs (which inherently distribute across AZs via target groups), and they mistakenly think ALBs have a 'connection timeout' setting when the correct term is 'idle timeout'.
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 NLB (default) and set the idle timeout on the ALB to a fixed value.
Cross-zone load balancing is enabled by default on Network Load Balancers (NLBs) and ensures traffic is distributed evenly across targets in all Availability Zones, which is critical for high availability across three AZs. The idle timeout on an Application Load Balancer (ALB) is a fixed value (default 60 seconds, configurable from 1 to 4000 seconds) that controls how long the ALB keeps a connection open without data transfer, meeting the requirement for a fixed response timeout. This combination satisfies both requirements without conflicting settings.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable cross-zone load balancing on the ALB and set the idle timeout on the NLB.
Why it's wrong here
ALB cross-zone cannot be disabled; NLB does not have idle timeout.
- ✓
Enable cross-zone load balancing on the NLB (default) and set the idle timeout on the ALB to a fixed value.
Why this is correct
Correct: NLB cross-zone is on by default; ALB idle timeout is configurable.
- ✗
Disable cross-zone load balancing on the NLB and set the connection timeout on the ALB.
Why it's wrong here
Disabling cross-zone reduces availability; ALB uses idle timeout, not connection timeout.
- ✗
Enable cross-zone load balancing on the ALB and set the connection timeout on the NLB.
Why it's wrong here
ALB cross-zone is always on; NLB does not have connection timeout.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 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 ANS-C01 exam.