Description:
An Elastic Load Balancing (ELBv2) load balancer must have at least one listener configured. A listener is a process that listens for connection requests on a specific port and protocol. Without a listener, the load balancer will not be able to receive traffic from clients.

Rationale:
Having a listener configured for an ELBv2 load balancer is essential for its functionality. Without a listener, the load balancer will not be able to receive traffic from clients, and therefore will not be able to distribute traffic to backend servers.

Impact:
If an ELBv2 load balancer does not have a listener configured, it will not be able to receive traffic from clients. This will prevent the load balancer from distributing traffic to backend servers, which can result in decreased performance or even service outages.

Default Value:
AWS will recommend that you create at least one listener for an ELBv2 load balancer when you create the load balancer.

Pre-requisites:

  • You must have the AWS CLI installed and configured.
  • You must have access to the AWS Management Console.

Remediation Steps:

  1. To remediate this issue, you must create a listener for the ELBv2 load balancer.
  2. You can do this using the AWS CLI or the AWS Management Console.

Test Plan:

  1. To test that the listener has been created, you can use the AWS CLI or the AWS Management Console to verify that the load balancer has a listener configured.
  2. You can also try to connect to the load balancer from a client. If you are able to connect, then the listener has been created successfully.

Implementation Plan:

AWS CLI:

aws elbv2 create-listener --load-balancer-arn <load-balancer-arn> --protocol <protocol> --port <port>


AWS Management Console:

  1. Go to the AWS Management Console and navigate to the ELBv2 load balancers page.
  2. Select the load balancer that you want to create a listener for.
  3. Click the "Listeners" tab.
  4. Click the "Create listener" button.
  5. In the "Protocol" field, select the protocol for the listener.
  6. In the "Port" field, enter the port for the listener.
  7. Click the "Create" button.

Backout Plan:
To back out the changes, you can delete the listener that you created.

Note:

  • The default protocol for an ELBv2 listener is HTTP.
  • The default port for an ELBv2 listener is 80.

Reference:
https://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/