Overview
Module: Module 1: Infrastructure & Addressing
Activity type: Lesson (Orient → Recall → Learn → Explain → Reflect)
Learning objective: Given two Compose services, the learner can place them on an isolated user-defined network, call one service by DNS name from the other, and explain host-port publish versus container-to-container traffic.
Bloom level: Analyze
Mastery unlock for this topic: reading done + Feynman complete + quiz ≥80% (when scored) + lab gate + homework submitted
Learning objective
Given two Compose services, the learner can place them on an isolated user-defined network, call one service by DNS name from the other, and explain host-port publish versus container-to-container traffic.
Why this matters
Wrong networking is the #1 silent failure in ARR and Home Assistant stacks: ‘it works in the browser on the host’ but containers cannot see each other: or everything is published to the LAN by accident.
Prior-knowledge check
Answer briefly before reading Instruction. Wrong answers are useful: they show what to review.
- What does a port number identify?
- What is DNS used for?
- If two containers share a Docker network, do they need published host ports to talk to each other?
Learn
Complete the module reading first:
Then review the worked example inside that reading (I do).
Guided practice (We do)
We do: hints allowed. Check your reasoning against Instruction.
With the lesson open, trace one packet path: browser → host port → container A → DNS name → container B. Label each hop.
Feynman teach-back: required
Required. Do not skip.
Explain
Describe Docker networks, DNS service discovery, and why localhost inside a container is not your PC in your own words. No copying the lesson verbatim.
Simplify
Explain the same idea to a 12-year-old. If you use a technical word, define it.
Example
Analogy: apartment intercoms (container DNS) vs listing your home phone number on a billboard (publishing ports).
Weak spot
What part was hard to explain? That is where your understanding is thin.
Retry
Return to that part of Instruction, restudy it, then rewrite a clearer explanation below.
Mastery note: a completed Feynman teach-back is required before the next class unlocks: “I get it” without explanation does not count.
Answers save in this browser (localStorage). Completing all five fields is part of the mastery unlock.
Reflection
Where did you confuse host localhost with container localhost, and how will you check DNS next time?
Also answer:
- What did I learn?
- What did I struggle with?
- How does this connect to earlier classes?
Spiral hook
Prowlarr→Sonarr (Class 5), HA add-ons (8–10), Wyoming voice (11–12), and n8n (14) all depend on this model. Class 15 (IPv4) explains same-LAN vs gateway when Docker networking meets your home router.