What is the role of ports in the target group of the application load balancer?

Question

When setting up the load balancer, I understand that it consists of a listener port, a target group port, and an instance port (ip port).

I think that the load balancer goes to the target group through the listener port and traffic is divided according to the instance port in the target group.

Then, the target group port does not seem to affect the load balancing. What is the role of the target group port?

Accepted Answer

The target group port is the **default** port if you register the target (e.g. an instance ID) without specifying the port.

A brief description is available here: https://docs.aws.amazon.com/cli/latest/reference/elbv2/register-targets.html

> By default, the load balancer routes requests to registered targets using the protocol and port for the target group. Alternatively, you can override the port for a target when you register it. You can register each EC2 instance or IP address with the same target group multiple times using different ports.

Answer

The Target group port defines the port on which instances receive traffic from Load Balancer and also the port on which health checks are performed (unless the health check port is overridden)

--Syd

What is the role of ports in the target group of the application load balancer?

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