A VPC can look perfectly healthy while an application inside it remains unreachable. The EC2 instance may be running, the required port may appear open, and the route table may contain what looks like the correct route. Yet the connection still fails. The challenge is that AWS networking is built from multiple independent components. A failure in any one of them can produce a similar symptom at the application level. A layer-by-layer investigation helps narrow the problem without making unnecessary configuration changes. Instead of changing several settings at once, examine the connection from the application outward and verify each part of the path. 1. Define the Connection First Before troubleshooting, describe exactly what is failing. For example: Source: EC2 application …
