grceng.academy
YAML lab 40 bonus XP

Repair the core-service plan

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Objectives

Halcyon Clinics permits small DNS lookups but larger replies fail. Its draft calls DNS UDP-only, describes DHCP as a TCP service, and restarts a cached answer's full lifetime whenever it is read.

Write a service plan from the fixture: identify the DNS destination port and both transports, the initial DHCP client and server ports and ordered exchange, then calculate cache lifetime and state the missing corroboration needed before claiming data transfer.

Approved requirements and observation

DNS: allow both standard transports to the internal resolver only.
DHCP: initial IPv4 allocation, no existing lease.
Cache: original TTL 300 seconds; elapsed 120 seconds; no refresh.
Claim to assess: a DNS query alone proves data transfer.
Evidence requirement: name a flow record or packet capture as corroboration.

Checks the server runs (6)

  • Correct DNS destination
  • Support both DNS transports
  • Separate client and server ports
  • Order the initial allocation
  • Calculate remaining lifetime
  • Bound the transfer claim

Check names are all you see here: the expectations that decide pass or fail, and the reference solution, stay on the server.

Step-by-step hints

The guided walkthrough, in full. It is free: no XP cost, and it does not touch the paid hint ladder or the reveal gate.

  1. Step 1

    Identify the resolver service

    Find its standard destination in the port conventions, independently of the chosen transport.

    Correct DNS destination

  2. Step 2

    Allow fallback

    Consider both a small answer and a truncated answer that requires a different transport.

    Support both DNS transports

  3. Step 3

    Separate DHCP endpoints

    Use the sending client and listening server roles from the initial broadcast example.

    Separate client and server ports

  4. Step 4

    Sequence allocation

    Use four list entries in temporal order: solicitation, proposal, selection and confirmation. Use the protocol message names from the lesson.

    Order the initial allocation

  5. Step 5

    Age the entry

    Apply elapsed seconds to the original lifetime without resetting it when read.

    Calculate remaining lifetime

  6. Step 6

    Limit the assertion

    Use a YAML boolean for whether a name query alone proves transfer; name a network artefact capable of corroborating subsequent communication.

    Bound the transfer claim

Rules summary

  • XP on pass

    40 bonus XP the first time every check goes green.

  • Paid hints

    2 available. Each costs 25% of the lab XP (about 10 XP).

  • Reveal solution

    Scores 0 XP and unlocks only after 3 check runs.

  • Attempt cap

    60 check runs per learner. The runner warns you in the last 10.

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  • Walkthrough

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