Questions 22 to 24

Explanations for questions 22 to 24

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Question 22

You recently noticed that your Network Load Balancer (NLB) in one of your VPCs is not distributing traffic evenly between EC2 instances in your AZs. There are an odd number of EC2 instances spread across two AZs. The NLB is configured with a TCP listener on port 80 and is using active health checks.

What is the most likely problem?

  1. There is no HTTP listener.
  2. Health checks are failing in one AZ due to latency.
  3. NLB can only load balance within a single AZ.
  4. Cross-zone load balancing is disabled.

Correct Answer: 4

Explanation: Without cross-zone load balancing enabled, the NLB will distribute traffic 50/50 between AZs. As there is an odd number of instances across the two AZs, some instances will not receive any traffic. Therefore enabling cross-zone load balancing will ensure traffic is distributed evenly between available instances in all AZs.

The diagram below shows an ELB with cross-zone load balancing enabled:

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