Port Connectivity and Firewall Troubleshooting Questions

Techniques for diagnosing port level connectivity and firewall related failures. Topics include how Transmission Control Protocol and User Datagram Protocol connections are established, differences between well known and ephemeral ports, service binding to interfaces and addresses, connection state semantics in stateful firewalls, and network address translation and port forwarding behaviors. Candidates should demonstrate how to inspect listening services and sockets, perform connection testing and port scans from multiple vantage points, validate firewall rule sets, and analyze packet captures for handshake failures, resets, or dropped traffic. Include cloud provider specifics such as security group rules, load balancer listener configuration, and validating end to end access paths.