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Domains & DNS

Name resolution and the records that matter.

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This course has 3 lessons. Start with the first one and use the next / previous links at the bottom of each lesson — the sidebar keeps the whole course in order.

Lessons

  1. How name resolution worksStub, recursive and authoritative servers, the path a lookup takes, and how to read dig output without guessing.
  2. Record types that matterA, AAAA, CNAME, MX, TXT and CAA - what each one does, how they interact, and where they collide.
  3. TTL, propagation and common mistakesWhat TTL really controls, how to migrate a domain safely, and the misconfigurations that cause outages.

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Last refreshed 2026-09-17.