Question

A SysOps administrator deploys web servers in a public subnet fronted by an internet-facing load balancer. Inbound HTTPS on port 443 works, but users report that responses time out intermittently. The subnet's network ACL has an inbound rule allowing TCP 443 from 0.0.0.0/0 and an outbound rule allowing only TCP 443 to 0.0.0.0/0. Security groups on the instances allow all necessary traffic. VPC Flow Logs show ACCEPT for inbound requests but REJECT for outbound packets. What is the most likely cause?

Accepted Answer

The network ACL outbound rules do not allow the ephemeral port range required for return traffic to clients

Answer

The security group is missing an outbound rule for port 443, blocking the responses

Answer

The route table lacks a default route to the internet gateway, dropping outbound packets

Answer

The instances are failing EC2 status checks, causing intermittent packet loss