Cross-Zone Load Balancing

Ensuring traffic is properly balanced across resources is critical in a cloud environment designed for high availability. This lesson covers cross-zone load balancing in AWS Elastic Load Balancing (ELB) and its behavior across Availability Zones (AZs). We’ll start by exploring how traffic is normally handled in AWS across zones, the default routing logic of ELBs, and what happens when cross-zone is not enabled. Then, we’ll dive into how cross-zone load balancing works, identify situations where enabling it makes sense, and evaluate the associated costs, especially for Network Load Balancers (NLBs). We’ll also learn about the performance gains, best practices, and potential pitfalls. Finally, we’ll discuss how to enable cross-zone via the AWS Management Console and CLI, and close with a quiz to solidify our understanding.

Cross-zone load balancing in AWS ELB distributes traffic evenly across all healthy targets in all AZs, helping maintain performance and resiliency.

How cross-zone balancing works

Cross-zone load balancing allows ELB to ...