Classic Load Balancer should span multiple Availability Zones

Severity: Medium

Resource Types: AWS::ELB::LoadBalancer

Description

This control checks whether a Classic Load Balancer has been configured to span multiple Availability Zones. The control fails if the Classic Load Balancer does not span multiple Availability Zones.

A Classic Load Balancer can be set up to distribute incoming requests across Amazon EC2 instances in a single Availability Zone or multiple Availability Zones. A Classic Load Balancer that does not span multiple Availability Zones is unable to redirect traffic to targets in another Availability Zone if the sole configured Availability Zone becomes unavailable.

Remediation

For information on how to add Availability Zones to a Classic Load Balancer, see Add or remove Availability Zones in the User Guide for Classic Load Balancers.