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Domains & DNS

Name resolution and the records that matter.

Domains & DNS is taught here in 14 lessons, running from How name resolution works through to Migrating DNS providers without downtime. Each lesson takes one topic, shows the working code, and links onward to the next, so the course can be read straight through in order.

TrackBuilding a Website
Lessons14
LevelBeginner to intermediate
Reading timeabout 3 hours
PrerequisitesHelpful, but not required: SEO Basics

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.
  4. The DNS hierarchy, zones and delegationZones and zone files, NS records and delegation, the SOA fields that actually matter, glue records, and why a zone is not the same thing as a domain.
  5. Registrars, registries and managing a domainWho does what in the registration chain, transfers and locks, expiry and auto-renew, nameserver delegation, and how to choose a DNS provider.
  6. Subdomains, wildcards and delegation strategiesCreating and delegating subdomains, the risks of wildcard records, per-subdomain nameservers, and naming conventions that still make sense at scale.
  7. Email DNS: MX, SPF, DKIM and DMARCMX priority and routing, SPF syntax and its lookup limit, publishing and rotating DKIM keys, DMARC policy and reporting, and where BIMI fits.
  8. Troubleshooting DNS with dig and online toolsThe dig flags worth knowing, tracing delegation, asking authoritative servers directly, reading TTLs and status codes, and spotting inconsistent answers.
  9. DNS as code: providers and TerraformManaging a hosted zone from code, writing records in Terraform, importing an existing zone safely, and reviewing DNS changes like any other change.
  10. DNS and CDNs: apex CNAME, ALIAS and flatteningWhy the apex cannot be a CNAME, what ALIAS and ANAME records do, how providers flatten them, and how to validate a CDN delegation.
  11. IPv6 and dual-stack DNSAAAA records and dual-stack delivery, happy eyeballs, IPv6-only clients behind NAT64 and DNS64, and how to test whether a site really works over IPv6.
  12. Anycast, GeoDNS and traffic steeringAnycast routing and where it fails, latency and geolocation policies, weighted and failover records with health checks, and when steering adds more risk than value.
  13. DNSSEC and DNS securitySigning a zone and the chain of trust, DS records and key rollover, validating resolvers, the misconfigurations behind DNSSEC outages, and other DNS-layer attacks.
  14. Migrating DNS providers without downtimeInventorying a zone, matching TTLs and provider behaviour, a staged nameserver cutover, verifying email and verification records, and rolling back.

More in Building a Website

SEO Basics Web Hosting CDNs & Caching Accessibility

FAQ

How long does the Domains & DNS course take?
It has 14 lessons, about 3 hours of reading. Expect roughly twice that if you type out and run every example.
Do I need prior experience for Domains & DNS?
Not strictly. It helps to have read SEO Basics first, because some lessons build on it, but every lesson explains its own assumptions.
What should I read after Domains & DNS?
Continue with Web Hosting (14 lessons), the next course in Building a Website.