Elastic Load Balancer Does Not Have Cross-Zone Load Balancing Enabled

Overview

This check examines whether cross-zone load balancing is activated for Classic Load Balancers (CLBs). The check does not pass if cross-zone load balancing is not turned on for a CLB.

A load balancer node allocates traffic solely among the registered targets within its designated Availability Zone. Disabling cross-zone load balancing means that each load balancer node distributes traffic exclusively among the registered targets in its assigned Availability Zone. This configuration may lead to uneven distribution of traffic if the number of registered targets varies across Availability Zones, potentially resulting in instances in one zone being more heavily utilized than those in another. Activating cross-zone load balancing ensures that each load balancer node for your Classic Load Balancer evenly distributes requests across all registered instances in all enabled Availability Zones.

Vendor

AWS

Cloud Service

ELB

Related Controls

ELB.9

Severity

3

Item Types

AWS::ElasticLoadBalancing::LoadBalancer