Home » Amazon » AWS Certified Solutions Architect - Associate » Which of the following features ensures even distribution of traffic to Amazon EC2 instances in multiple Availability Zones registered with a load balancer?
Which of the following features ensures even distribution of traffic to Amazon EC2 instances in multiple Availability Zones registered with a load balancer?
A. Elastic Load Balancing request routing
B. An Amazon Route 53 weighted routing policy
C. Elastic Load Balancing cross-zone load balancing
D. An Amazon Route 53 latency routing policy
Correct Answer: C
Explanation/Reference:
Explanation:
Cross-zone load balancing is always enabled for an Application Load Balancer and is disabled by default for a Classic Load Balancer. If cross-zone load balancing is enabled, the load balancer distributes traffic evenly across all registered instances in all enabled Availability Zones. If cross-zone load balancing is disabled, the load balancer distributes traffic evenly across all enabled Availability Zones. For example, suppose that you have 10 instances in Availability Zone us-west-2a and 2 instances in us-west-2b. If cross-zone load balancing is disabled, the requests are distributed evenly between us-west-2a and us-west-2b. As a result, the 2 instances in us-west-2b serve the same amount of traffic as the 10 instances in us-west-2a. However, if cross-zone load balancing is enabled, the load balancer distributes incoming requests evenly across all 12 instances.
http://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/how-elastic-load-balancing-works.html
