> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vms.verolabs.co/llms.txt
> Use this file to discover all available pages before exploring further.

# Probe: dns_check

> Check DNS record resolution

## Description

The `dns_check` probe performs DNS lookups and validates results. Supports record types A, AAAA, CNAME, MX, TXT. Allows custom DNS resolver and expected value assertions.

## Config fields

| Field            | Type       | Required | Default         | Description                                                               |
| ---------------- | ---------- | -------- | --------------- | ------------------------------------------------------------------------- |
| `type`           | `string`   | Yes      | —               | Must be `"dns_check"`                                                     |
| `host`           | `string`   | Yes      | —               | Domain name to resolve                                                    |
| `recordType`     | `string`   | No       | `"A"`           | Record type: `A`, `AAAA`, `CNAME`, `MX`, `TXT`                            |
| `resolver`       | `string`   | No       | system resolver | Custom DNS resolver (host or host:port). Defaults to `:53` if no port     |
| `expectedValues` | `string[]` | No       | —               | DNS values that must be present in the result. Any missing value → `down` |

## Metrics

| Metric                     | Type   | Unit | Description    |
| -------------------------- | ------ | ---- | -------------- |
| `vms.dns_check.status`     | status | —    | `up` or `down` |
| `vms.dns_check.latency_ms` | gauge  | ms   | Lookup time    |

## Example config

```json theme={null}
{
  "type": "dns_check",
  "host": "app.verolabs.co",
  "recordType": "A",
  "expectedValues": ["10.0.0.10"]
}
```

## Notes

* CNAME trailing dots are automatically stripped before comparison.
* MX records compare hostname only (no priority).