Networking Basics — ip, ss, curl — Linux & Shell Scripting

Linux networking underpins every DevOps tool and service: containers communicate through virtual networks, CI/CD pipelines pull packages over HTTPS, health checks probe TCP ports, and load balancers route traffic based on IP rules. Understanding how to inspect network interfaces, diagnose connectivity problems, and test HTTP endpoints from the command line is as essential as understanding the filesystem. Networking problems are among the most common causes of deployment failures and production incidents.

The tools covered in this lesson — `ip`, `ss`, `curl`, `dig`, and `netcat` — are the first line of diagnosis for any networking issue. Before reaching for Wireshark, tcpdump, or a cloud console, an experienced engineer checks whether the interface is up, whether the correct address is assigned, whether the service is listening on the expected port, and whether a basic HTTP request receives the expected response. These five checks resolve the majority of networking incidents.

This lesson builds the mental model of Linux networking from the interface layer through TCP sockets to HTTP — following the path a CricketPulse API request takes from the client's TCP SYN packet to the application's JSON response. Each concept is grounded in a concrete diagnostic scenario: a deployment where the service is not reachable, a load balancer health check that is failing, and an SSL certificate that has expired.

Analogy🏏Cricket

🏏 Think of it like cricket: The match itself is the kernel — real computation at the hardware level. The commentators translating that action into words for the audience are the shell: they take raw events and present them in a form humans can understand and interact with. The television set in your living room is the terminal emulator: it displays the commentary but does not participate in the match.Just as switching from one broadcaster to another changes commentary style but not the underlying match, switching between Linux distributions changes shell defaults and package manager but not the kernel. Just as Star Sports and Sony Six both cover the same IPL match with different graphics packages, Ubuntu and Alpine both run the same kernel with different userspace tools.The insight is that these layers are genuinely separate, which is why you can swap any one of them independently.