---
applyTo: "**/*.md,**/*.rst,**/*.txt"
---

## Doc Linter Rules

Every pull request is automatically linted by `scripts/doc-linter.py`.
It checks **only changed files** for two things: IP address usage
and line length. MyST Markdown (`.md`), legacy RST (`.rst`), and
`.txt` includes are all linted.

### IP Address Rules

The linter rejects public IP addresses that are not reserved for documentation.

**Use these documentation-reserved addresses (no suppression needed):**

| Type | Range | RFC |
|------|-------|-----|
| IPv4 | `192.0.2.0/24` (TEST-NET-1) | RFC 5737 |
| IPv4 | `198.51.100.0/24` (TEST-NET-2) | RFC 5737 |
| IPv4 | `203.0.113.0/24` (TEST-NET-3) | RFC 5737 |
| IPv6 | `2001:db8::/32` | RFC 3849 |

**These are allowed without suppression (not flagged by linter):**

| Type | Range | Why |
|------|-------|-----|
| RFC 1918 private | `10.0.0.0/8` | Private address space |
| RFC 1918 private | `172.16.0.0/12` | Private address space |
| RFC 1918 private | `192.168.0.0/16` | Private address space |
| Loopback | `127.0.0.0/8` | Loopback range |
| Link-local | `169.254.0.0/16` | Link-local |

**These require `stop/start_vyoslinter` suppression:**

% stop_vyoslinter

| Example | Why suppression is needed |
|---------|--------------------------|
| `8.8.8.8` (Google DNS) | Real public IP, not documentation-reserved |
| `64:ff9b::/96` (NAT64) | Well-known prefix, not in doc ranges |
| Real provider IPs in examples | Authenticity matters for the example |

% start_vyoslinter

### Line Length Rules

Maximum 80 characters per line. The line-length check is
**skipped** inside fenced code:

- MyST / Markdown: ` ```...``` ` and `:::...:::` fenced blocks
  (any info string, including ` ```{eval-rst} `, ` ```{cfgcmd} `,
  etc.).
- RST: lines indented under `.. code-block::` directives.

### Suppression Syntax

When real public IPs or long lines are unavoidable, wrap the block.
The marker form depends on the surrounding parser:

**MyST Markdown (`.md`)** — use the MyST comment form:

% stop_vyoslinter

````md
% stop_vyoslinter

```
set system name-server '8.8.8.8'
```

% start_vyoslinter
````

% start_vyoslinter

**RST (`.rst`) and `.txt` includes** — use the RST comment form:

% stop_vyoslinter

```rst
.. stop_vyoslinter

.. code-block:: none

   set system name-server '8.8.8.8'

.. start_vyoslinter
```

% start_vyoslinter

**Inside a `{eval-rst}` block in MyST** — the embedded content is parsed
as RST, so the RST form (`.. stop_vyoslinter`) matches the surrounding
parser. The linter recognizes marker lines only in the parser context
where they apply, including RST markers inside `{eval-rst}` blocks.

**Rules for suppression markers:**

- Place the stop marker on its own line, immediately before the content.
- Place the start marker on its own line, immediately after the content.
- Always re-enable the linter — never leave it stopped for the rest
  of the file.
- Suppress the smallest possible region.
- Do NOT use suppression for content that can use
  documentation-reserved addresses instead.

### Common Mistakes

- Removing `stop/start_vyoslinter` markers without fixing the
  underlying issue (exposes the line to the linter and fails CI).
- Using real public IPs when documentation addresses would work just as well.
- Adding suppression markers around content that only has private
  (RFC 1918) addresses or `0.0.0.0/0` — these are allowed and don't
  need suppression.
- Mixing marker forms (using `% stop_vyoslinter` inside an
  `{eval-rst}` block, or `.. stop_vyoslinter` in plain MyST prose).