When one website loads instantly but another times out, the immediate assumption is often that the second site is down. This case study challenges that assumption by walking through a structured diagnostic process. The author starts with a simple curl command, observes the timeout, and then methodically tests each layer of the network stack: DNS resolution, TCP connectivity, and HTTP response. The key insight is the importance of collecting evidence at each step rather than jumping to conclusions. The post demonstrates how to use tools like dig, nslookup, and curl with verbose output to pinpoint whether the issue lies in local DNS configuration, upstream resolvers, or the target server's network path. The result is a reusable troubleshooting template that any engineer can apply to similar 'site X doesn't load' problems. The emphasis on building a complete evidence chain—from initial symptom to root cause—makes this a valuable reference for network debugging.
A practical case study on diagnosing a site-specific DNS failure, showing how to systematically isolate the problem layer and build an evidence chain.