Module 09
DNS
How names become addresses. Walk a lookup from resolver to root to authoritative server, read the records that come back and see what caching saves.
Start lesson 1
Who answers for a name? · 8 min · free, no account
ApplicationOpen now
What you'll operate
- Resolvers and name servers
- Record types
- Caching and TTLs
- lessons
- 6
- minutes
- 48
Lessons in this module
- 1Who answers for a name?Meet the three kinds of DNS machine, read a name as a path through a tree, and see how the tree is shared out.Free, no account8 min
- 2How does a resolver find an address?Play a full lookup from the root down, tell a referral from an answer, and see where a warm cache lets the search start.Plus8 min
- 3Which record answers which question?Read a zone line by line, pick the record a browser or a mail server needs, and turn an address back into a name.Plus8 min
- 4What happens when a name is an alias?Follow CNAME records inside one zone and across two, then learn the three rules that keep aliases from breaking a zone.Plus7 min
- 5How long is an answer good for?Watch a TTL count down in a resolver's cache, see how missing names are cached too, and predict when a change becomes visible.Plus8 min
- 6What can go wrong with a lookup?See an answer outgrow UDP, find a wrong resolver setting, and learn what a forged reply needs and what signing and encryption each protect.Plus9 min
Lesson 1 is open to everyone, with no account. The other lessons in this module are part of Plus.