Target Groups with ALB

Target groups

Target groups are a logical grouping of targets (EC2 instances or ECS). Targets are the endpoints and can be EC2 instances, ECS containers, or IP addresses. Target groups can exist independently from the ALB.

• Target groups can have up to 1000 targets.
• A single target can be in multiple target groups.
• Only one protocol and one port can be defined per target group.
• The target type in a target group can be an EC2 instance ID, IP address (must be a valid private IP from an existing subnet), or AWS Lambda Function (ALB only).
• Target groups are used for registering instances against an ALB or NLB.
• ALB can route to multiple target groups.
• Target groups are a regional construct.
• Health checks are defined per target group.

Limitations

• You cannot use public IP addresses as targets.
• You cannot use instance IDs and IP address targets within the same target group.
• A target group can only be associated with one load balancer.

The diagram given below illustrates the basic components. Notice that each listener contains a default rule, and one listener contains another rule that routes requests to a different target group. One target is registered with two target groups.