grceng.academy
Review lab 40 bonus XP

Review six boundary claims

Start labRead the room

Objectives

A change board has six networking claims to approve. Its chair says all are safe because the virtual networks use private addresses.

Judge each claim under this room's filter and routing model. Accept technically sound claims; reject unsound ones using the single most specific reason code. Treat each line independently.

Verdicts are accept or reject. Every rejection needs one reason code from: false-transit | unsupported-deny | missing-return | unproved-private-path.

Boundary review statements

CN-1 | A-B peering and B-C peering automatically allow A-C transit.
CN-2 | A worker's NAT default permits updates and matching replies, but not unsolicited inbound sessions.
CN-3 | Add an explicit deny rule to the interface security group to override its broad allow.
CN-4 | An inbound-only subnet ACL permission is sufficient for TCP replies because the ACL tracks sessions.
CN-5 | The interface private endpoint exists, so no DNS or private-path test is needed to prove clients use it.
CN-6 | An ACL deny numbered 100 shadows a matching allow numbered 200, even if the allow names a narrower source.

Checks the server runs (3)

  • Every line in the fixture carries a verdict
  • Accept and reject land on the right lines
  • Each rejection cites a valid reason code

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

    Read the request before the artefact

    Use the room's explicit semantics rather than importing a different platform's behavior.

  2. Step 2

    Judge every line, including the boring ones

    Make one judgement for every claim, including the claims that require no change.

    Every line in the fixture carries a verdict

  3. Step 3

    Separate what is wrong from what is merely ugly

    Trace a packet and its reply for the filtering claims. For connectivity claims, ask what route or name-resolution evidence is actually available.

    Accept and reject land on the right lines

  4. Step 4

    Say why, in the vocabulary the programme uses

    Match the violated mechanism to a reason code: transit, filter capability, reverse-direction permission, or proof of the service path.

    Each rejection cites a valid reason code

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.

  • Drafts

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  • Walkthrough

    Always free and never penalised: use it before spending a hint.