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Difficulty: MediumAuto Scaling and Elastic Load Balancing (ELB)

A gaming company hosts a mobile leaderboard application on Amazon EC2 instances in an Auto Scaling group (ASG). The instances are registered with a target group for an Application Load Balancer (ALB). The leaderboard application listens on custom TCP port 80808080, but the ALB shows all EC2 instances as unhealthy. A solutions architect verifies that the application is running correctly on the instances. Which two actions should the solutions architect take to resolve the health check issues? (Select two.)

  1. Update the ALB target group health check configuration to use port 80808080 or select the traffic port option.Answer
  2. Configure the security group of the EC2 instances to allow inbound TCP traffic on port 80808080 from the security group of the ALB.Answer
  3. C
    Modify the target group health check port to port 8080 because Application Load Balancers can only perform HTTP health checks on standard web ports.
  4. D
    Remove all outbound rules from the subnet's Network ACL because Network ACLs are stateful and will automatically allow return traffic.
  5. E
    Change the Amazon Route 53 routing policy to Latency routing pointing directly to the EC2 instances to bypass the Application Load Balancer.

Answer

To resolve the health check issues, the target group health check port must match the application port (port 80808080), and the EC2 instances' security group must permit inbound traffic on port 80808080 from the load balancer.
The correct actions are to update the target group health check to query the custom port 80808080 (or select the traffic port option) and configure the EC2 instances' security group to allow inbound traffic on port 80808080 from the ALB's security group. This ensures the load balancer can reach the application to evaluate its health and forward client traffic.

Step-by-Step Solution

1
Verify and align the health check port configuration.
Changing the target group health check port to port 80808080 or traffic-port ensures the ALB targets the active application port.
By default, if the target group is configured on a custom port but the health check is set to a default port (like port 8080), the instances will be marked unhealthy.
2
Ensure network connectivity between the ALB and the EC2 instances.
Updating the EC2 instance security group to allow port 80808080 inbound from the ALB's security group allows the health check requests and application traffic to flow.
Security groups require an explicit inbound rule for traffic to enter the instances.

Key Concept

Auto Scaling and Elastic Load Balancing health check configuration and security group alignment
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Topics

Auto Scaling and Elastic Load Balancing (ELB)

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