Episode 97 — DNS vs routing vs firewall: fast isolation with minimal commands

Linux+ often tests network failures by making multiple causes plausible, then rewarding the candidate who isolates the layer quickly. This episode teaches fast isolation between DNS, routing, and firewall causes using minimal commands and a strict workflow. You’ll learn the exam-critical distinction: DNS problems prevent name-to-IP resolution, routing problems prevent packets from reaching the target network, and firewall problems allow reachability at one layer but block specific ports or flows. The goal is to help you interpret symptoms like “can ping IP but not hostname,” “can resolve but can’t connect,” or “works on one port but not another,” and to choose the next step that proves the cause rather than adding more guesses.

we apply a layered isolation approach that scales from simple hosts to complex services. You’ll practice confirming resolution first when hostnames are involved, then confirming routing to the resolved address, then confirming service-level reachability by testing the specific port and verifying server-side listening and policy. We also cover exam traps: assuming a firewall issue when the service isn’t bound, blaming DNS when the route is missing, and “fixing” by disabling security controls instead of correcting the precise rule or configuration. Finally, you’ll learn best practices aligned with exam intent: keep tests small and reversible, record what you proved at each step, and validate from both client and server perspectives so the final diagnosis is defensible and the remediation doesn’t create new exposure. Produced by BareMetalCyber.com, where you’ll find more cyber audio courses, books, and information to strengthen your educational path. Also, if you want to stay up to date with the latest news, visit DailyCyber.News for a newsletter you can use, and a daily podcast you can commute with.