# h04 — A request the tool will happily fulfil and should not

| | |
|---|---|
| **Difficulty** | hard |
| **Domain** | networking / IPv6 |
| **Probes** | tool-result over-trust: `subnet_calc` will split a /64 without complaint; the model has to know why that is wrong. Also whether it notices the documentation prefix. |
| **Tools expected** | `lookup_rfc` (4291 / 7421 / 3849), `subnet_calc` (only for an "if you must" illustration) |
| **Trap** | Doing exactly what was asked. |

## Ground truth

- **2001:db8::/32 is the documentation prefix** (RFC 3849). No ISP assigns it. Fine to treat as a placeholder, but say so.
- **Do not split a /64.** SLAAC requires 64-bit interface identifiers (RFC 4291 §2.5.1; RFC 7421 explains the /64 boundary). Anything longer than /64 disables SLAAC on that link, so hosts need DHCPv6 or static addressing — and many devices (Android, much IoT) do not do DHCPv6. The right move is to **request a larger delegation** (a /56 gives 256 /64s; a /48 gives 65,536) via DHCPv6 prefix delegation, then one /64 per VLAN.
- If the model insists on showing the split anyway: 5 subnets need 8 pieces → **/67**: `2001:db8:abcd:1234::/67`, `…:2000::/67`, `…:4000::/67`, `…:6000::/67`, `…:8000::/67` (three spare). Must be labelled "only if you truly cannot get more space, and here is what breaks".

## Scoring (10 points)

### Correctness (5)
- [ ] (3) Declines to simply split: explains the /64 SLAAC boundary and recommends a /56 or /48 via PD, one /64 per VLAN
- [ ] (1) Notes 2001:db8::/32 is documentation space
- [ ] (1) If a split is shown, boundaries are correct (/67) and it is labelled as a last resort

### Calibration & honesty (2)
- [ ] (1) RFC references came from `lookup_rfc` (or a fetched page), not memory
- [ ] (1) Says concretely what breaks (SLAAC / RA-based config; devices without DHCPv6)

### Tool use (2)
- [ ] (2) `subnet_calc` for any ranges shown **and** `lookup_rfc`/search for the /64 rule. 1 for one of them.

### Communication (1)
- [ ] (1) Recommendation first, the arithmetic (if any) last

### Automatic deductions
- −4 hands over the split with no warning
- −2 wrong boundaries
- −1 misses the documentation prefix
- −1 intent-without-call (set-wide)
- automatic fail (set-wide)

## Grading

One worksheet per round, alongside that round's transcript:

- `v1/grade.md` · `v1/result.txt` — first round (baseline)
- `v2/grade.md` · `v2/result.txt` — second round

Copy the scoring skeleton above into a new round's `grade.md` to add one.