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DNS

Beginner → Advanced

The first domino in most outages. Master it.

Outcome

Diagnose 'it works here but not there' name-resolution problems in minutes.

The ladder

Beginner
  • ▸Names → addresses
  • ▸Resolvers
  • ▸Record types (A/AAAA/CNAME/MX)
  • ▸/etc/hosts
Intermediate
  • ▸Recursive vs authoritative
  • ▸Caching & TTL
  • ▸Reading dig output
  • ▸Search domains
Advanced
  • ▸Split-horizon DNS
  • ▸Conditional forwarders
  • ▸Delegation
  • ▸Resolution failure triage

Example lessons

lesson

How DNS really resolves

lesson

Why /etc/hosts wins over DNS

lesson

TTL and the propagation myth

Practise with puzzles

IntermediateDNS Works Here, Not There

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