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Difficulty: EasyElastic Load Balancing Health Checks and Troubleshooting

An administrator registers a fleet of Amazon EC2 instances running a web application on port 8080 to an Application Load Balancer (ALB) target group. The ALB's target group health checks are configured to use the default HTTP settings on port 80. As a result, the ALB marks all instances as unhealthy. Which action should the administrator take to resolve this health check failure?

  1. Modify the target group settings to override the health check port to 8080.Answer
  2. B
    Update the health check path to a static file path like /health while keeping port 80.
  3. C
    Change the Route 53 routing policy to active-passive failover to bypass the unhealthy targets.
  4. D
    Associate an Internet Gateway with the private subnet's route table to allow the ALB to reach the instances.

Answer

Modify the target group settings to override the health check port to 8080.
The correct action is to modify the target group settings to override the health check port to 8080. This aligns the destination port of the health check packets with the port on which the web application on the EC2 instances is configured to listen.

Step-by-Step Solution

1
Identify the port where the backend application is listening.
The application is listening on port 8080.
Health checks must be sent to the correct port to receive a response.
2
Compare the application port with the target group's health check configuration.
There is a port mismatch (health check port is 80, application port is 8080).
This port mismatch explains why the target group health checks are failing.
3
Modify the health check port in the target group settings to match the application port.
The health checks are sent to port 8080, and the targets become healthy.
This aligns the load balancer's requests with the backend application port.

Key Concept

Configuring Elastic Load Balancing target group health checks to align with backend application listening ports.
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Topics

Elastic Load Balancing Health Checks and Troubleshooting

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