Question

An e-commerce company is using an Elastic Load Balancer for its fleet of EC2 instances spread across two Availability Zones, with one instance as a target in Availability Zone A and four instances as targets in Availability Zone B. The company is doing benchmarking for server performance when cross-zone load balancing is enabled compared to the case when cross-zone load balancing is disabled. As a solutions architect, which of the following traffic distribution outcomes would you identify as correct? • With cross-zone load balancing enabled, one instance in Availability Zone A receives 20% traffic and four instances in Availability Zone B receive 20% traffic each. With cross-zone load balancing disabled, one instance in Availability Zone A receives no traffic and four instances in Availability Zone B receive 25% traffic each • With cross-zone load balancing enabled, one instance in Availability Zone A receives 20% traffic and four instances in Availability Zone B receive 20% traffic each. With cross-zone load balancing disabled, one instance in Availability Zone A receives 50% traffic and four instances in Availability Zone B receive 12.5% traffic each • With cross-zone load balancing enabled, one instance in Availability Zone A receives 50% traffic and four instances in Availability Zone B receive 12.5% traffic each. With cross-zone load balancing disabled, one instance in Availability Zone A receives 20% traffic and four instances in Availability Zone B receive 20% traffic each • With cross-zone load balancing enabled, one instance in Availability Zone A receives no traffic and four instances in Availability Zone B receive 25% traffic each. With cross-zone load balancing disabled, one instance in Availability Zone A receives 50% traffic and four instances in Availability Zone B receive 12.5% traffic each

Answer 1

Cross-zone load balancing enables even traffic distribution across Availability Zones, while disabling it concentrates more traffic on one instance in Availability Zone A.

Step-by-step explanation:

When cross-zone load balancing is enabled, an Elastic Load Balancer distributes traffic evenly across the EC2 instances in both Availability Zones. In this case, one instance in Availability Zone A will receive 20% of the traffic, and the four instances in Availability Zone B will receive 20% each.

With cross-zone load balancing disabled, the traffic distribution is different. One instance in Availability Zone A will receive 50% of the traffic, while the four instances in Availability Zone B will receive 12.5% each.

Therefore, the correct traffic distribution outcomes are:

• With cross-zone load balancing enabled, one instance in Availability Zone A receives 20% traffic and four instances in Availability Zone B receive 20% traffic each.
• With cross-zone load balancing disabled, one instance in Availability Zone A receives 50% traffic and four instances in Availability Zone B receive 12.5% traffic each.

Learn more about Cross-zone Load Balancing