All checks
Medium
Classic Load Balancers should have cross-zone load balancing enabled
Confirms that cross-zone load balancing is enabled for Classic Load Balancers, distributing traffic evenly across all registered instances in all enabled Availability Zones. Without it, requests are split evenly between zones first, so a zone with fewer instances loads each of them more.
- service
- ELB
- severity
- Medium
- scope
- evaluated in every region
How to fix it
- Affects another check: With only one Availability Zone enabled this changes nothing, and ELB.10 stays failing until a second zone is added.
In the console
EC2 → Load balancers → the load balancer → Attributes → Availability Zone routing configuration
- Cross-zone load balancing
- On
With the AWS CLI
aws elb modify-load-balancer-attributes --load-balancer-name <load-balancer-name> --load-balancer-attributes CrossZoneLoadBalancing={Enabled=true} --region <region>With Terraform
resource "aws_elb" "this" {
cross_zone_load_balancing = true
listener {
lb_port = 80
lb_protocol = "http"
instance_port = 80
instance_protocol = "http"
}
}See which of your accounts this check is failing on.
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