Question

A media company runs a fleet of EC2 instances in private subnets that push telemetry to a single third-party analytics endpoint (one destination IP and port) over HTTPS. Traffic flows through a NAT gateway. During peak events, application logs show connection failures and the CloudWatch metric ErrorPortAllocation for the NAT gateway spikes above zero, even though bandwidth utilization is well below the NAT gateway's throughput limit. What is the MOST effective way to resolve these connection failures?

Accepted Answer

Deploy multiple NAT gateways across different subnets and distribute the private instances so their traffic uses different NAT gateways, increasing the pool of available source ports to the same destination.

Answer

Increase the NAT gateway's bandwidth by requesting a service quota increase for maximum throughput per NAT gateway.

Answer

Replace the NAT gateway with a NAT instance running on a larger instance type to raise the connection limit.

Answer

Enable cross-zone load balancing on the NAT gateway so connections are balanced across Availability Zones.