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

# DNS Monitor Configuration

> Configure your DNS monitor to verify record resolution.

### Basic Setup

Specify the domain and record type you want to check:

<Frame>
  <img className="block dark:hidden" src="https://mintcdn.com/checkly-422f444a/MmTYrkwl87Z39cap/images/dns-monitors/request.png?fit=max&auto=format&n=MmTYrkwl87Z39cap&q=85&s=9fb7c4a39ff92bdb359c947edcb1d10d" alt="DNS monitor setup interface showing domain, record type, dns server and protocol" width="2742" height="578" data-path="images/dns-monitors/request.png" />

  <img className="hidden dark:block" src="https://mintcdn.com/checkly-422f444a/MmTYrkwl87Z39cap/images/dns-monitors/request-dark.png?fit=max&auto=format&n=MmTYrkwl87Z39cap&q=85&s=190452ee61fab06598e627d63f945e05" alt="DNS monitor setup interface showing domain, record type, dns server and protocol" width="2742" height="578" data-path="images/dns-monitors/request-dark.png" />
</Frame>

* **Domain:** The domain you want to monitor (e.g. `checklyhq.com`)
* **Record type:** The DNS record to query. See [supported record types](/detect/uptime-monitoring/dns-monitors/overview#supported-dns-record-types) for the full list
* **DNS server:** Queries use 8.8.8.8 (Google DNS) by default with automatic failover to 1.1.1.1 (Cloudflare) and an internal AWS resolver on errors. You can specify a custom nameserver and port (e.g., `1.1.1.1:53` or `dns.google:53`) to test resolver-specific behavior
* **Protocol:** You can pin DNS queries to UDP-only or TCP-only

### Assertions

Assertions let you define what the expected result of a DNS query should be.

The raw and JSON responses are shown on the results page of a DNS monitor run and can be used as a reference when defining assertions.

<Frame>
  <img className="block dark:hidden" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/assertions.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=17b7dec454c6e0c604e0dfd0b0166754" alt="DNS monitor assertions and corresponding data fields" width="2848" height="478" data-path="images/dns-monitors/assertions.png" />

  <img className="hidden dark:block" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/assertions-dark.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=7b0779a613b9f345a2e2b379cb44d2e8" alt="DNS monitor assertions and corresponding data fields" width="2848" height="478" data-path="images/dns-monitors/assertions-dark.png" />
</Frame>

* **Response time:** The lookup time in milliseconds. Use this to set thresholds for failed lookups

* **Response code:** By default, DNS monitors pass when the return code is NOERROR and fail on error codes (FORMERR, SERVFAIL, NXDOMAIN, etc.). You can override this behavior by defining a custom return code assertion

* **Text answer:** The raw DNS response as plain text. Use this to check for specific strings in the response

* **JSON answer:** The DNS response parsed as JSON. This allows you to target specific fields using JSON path assertions. The response structure varies by record type. See [JSON response schemas](#json-response-schemas) below for all supported record types.

  With JSON path assertions, you can:

  * `$.Answer[0].TTL` → validate TTL values are within expected ranges
  * `$.Answer[0].data` → check specific IP addresses or record values
  * `$.Answer.length` → check how many records were returned
  * `$.Status` → verify the DNS response status code

  Learn more about JSON path assertions: [JSON responses with JSON path](/detect/assertions/#json-responses-with-json-path).

### JSON Response Schema

The DNS response is parsed into a structured JSON format. All responses share a common structure:

```json theme={null}
{
  "Answer": [
    // Array of answer records
  ],
  "Question": [
    {
      "name": "example.com.",
      "type": "A"
    }
  ],
  "Status": "NOERROR",
  "TC": false,
  "RD": true,
  "RA": true,
  "AD": false,
  "CD": false
}
```

**Key fields**:

* `Answer` - Array of DNS records returned
* `Question` - The DNS query that was made
* `Status` - Response status (NOERROR, NXDOMAIN, SERVFAIL, etc.)
* `TC` - Truncated flag
* `RD` - Recursion desired flag
* `RA` - Recursion available flag
* `AD` - Authenticated data flag
* `CD` - Checking disabled flag

<Accordion title="A Record (IPv4)">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "checklyhq.com.",
        "type": "A",
        "TTL": 27,
        "data": "18.66.102.85"
      },
      {
        "name": "checklyhq.com.",
        "type": "A",
        "TTL": 27,
        "data": "18.66.102.10"
      }
    ],
    "Question": [
      {
        "name": "checklyhq.com.",
        "type": "A"
      }
    ],
    "Status": "NOERROR",
    "TC": false,
    "RD": true,
    "RA": true,
    "AD": false,
    "CD": false
  }
  ```

  Common assertions:

  * `$.Answer[0].data` - Check specific IP address
  * `$.Answer[0].TTL` - Validate TTL value
</Accordion>

<Accordion title="AAAA Record (IPv6)">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "example.com.",
        "type": "AAAA",
        "TTL": 300,
        "data": "2606:2800:220:1:248:1893:25c8:1946"
      }
    ],
    "Question": [
      {
        "name": "example.com.",
        "type": "AAAA"
      }
    ],
    "Status": "NOERROR"
  }
  ```

  Common assertions:

  * `$.Answer[0].data` - Check IPv6 address
  * `$.Answer[0].TTL` - Validate TTL value
</Accordion>

<Accordion title="CNAME Record">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "www.example.com.",
        "type": "CNAME",
        "TTL": 300,
        "data": "example.com."
      }
    ],
    "Question": [
      {
        "name": "www.example.com.",
        "type": "CNAME"
      }
    ],
    "Status": "NOERROR"
  }
  ```

  Common assertions:

  * `$.Answer[0].data` - Verify canonical name target
</Accordion>

<Accordion title="MX Record">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "example.com.",
        "type": "MX",
        "TTL": 3600,
        "data": "10 mail.example.com."
      },
      {
        "name": "example.com.",
        "type": "MX",
        "TTL": 3600,
        "data": "20 mail2.example.com."
      }
    ],
    "Question": [
      {
        "name": "example.com.",
        "type": "MX"
      }
    ],
    "Status": "NOERROR"
  }
  ```

  Common assertions:

  * `$.Answer[0].data` - Check MX priority and mail server (format: "priority hostname")
</Accordion>

<Accordion title="TXT Record">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "example.com.",
        "type": "TXT",
        "TTL": 300,
        "data": "v=spf1 include:_spf.example.com ~all"
      }
    ],
    "Question": [
      {
        "name": "example.com.",
        "type": "TXT"
      }
    ],
    "Status": "NOERROR"
  }
  ```

  Common assertions:

  * `$.Answer[0].data` - Verify SPF, DKIM, or other TXT records
  * Text response contains `v=spf1` - Check for SPF record
</Accordion>

<Accordion title="NS Record">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "example.com.",
        "type": "NS",
        "TTL": 86400,
        "data": "ns1.example.com."
      },
      {
        "name": "example.com.",
        "type": "NS",
        "TTL": 86400,
        "data": "ns2.example.com."
      }
    ],
    "Question": [
      {
        "name": "example.com.",
        "type": "NS"
      }
    ],
    "Status": "NOERROR"
  }
  ```

  Common assertions:

  * `$.Answer[0].data` - Check specific nameserver
</Accordion>

<Accordion title="SOA Record">
  ```json theme={null}
  {
    "Answer": [
      {
        "name": "example.com.",
        "type": "SOA",
        "TTL": 3600,
        "data": "ns1.example.com. admin.example.com. 2024010100 7200 3600 1209600 3600"
      }
    ],
    "Question": [
      {
        "name": "example.com.",
        "type": "SOA"
      }
    ],
    "Status": "NOERROR"
  }
  ```

  **SOA data format**: `primary-ns responsible-email serial refresh retry expire minimum`

  Common assertions:

  * `$.Answer[0].data` - Verify SOA record (contains serial number and nameserver)
  * Text response contains expected serial number
</Accordion>

<Note>
  **Record type support**: DNS monitors currently support A, AAAA, CNAME, MX, NS, SOA, and TXT record types. Additional record types (SRV, CAA, PTR, etc.) may be added in future updates.
</Note>

### Response Time Limits

Define performance thresholds for degraded or failed states:

<Frame>
  <img className="block dark:hidden" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/response-time.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=83372953634c82dd57c9b27e685f5947" alt="DNS monitor response time limits interface" width="2878" height="516" data-path="images/dns-monitors/response-time.png" />

  <img className="hidden dark:block" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/response-time-dark.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=630a7ebfacba259adec25db063ffbc0e" alt="DNS monitor response time limits interface" width="2848" height="516" data-path="images/dns-monitors/response-time-dark.png" />
</Frame>

### Frequency

Set how often the monitor runs (every 10 seconds to 24 hours):

<Frame>
  <img className="block dark:hidden" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/frequency.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=56d58e1ab43d72502fd32e7678bf222d" alt="DNS monitor frequency selection interface" width="2848" height="478" data-path="images/dns-monitors/frequency.png" />

  <img className="hidden dark:block" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/frequency-dark.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=070450751ac17db8bf65a85c4ccb6f18" alt="DNS monitor frequency selection interface" width="2878" height="478" data-path="images/dns-monitors/frequency-dark.png" />
</Frame>

### Scheduling & Locations

<Frame>
  <img className="block dark:hidden" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/scheduling.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=8c6c65eb252f9602c0ab5f8ba3eeabdd" alt="DNS monitor scheduling strategy and location selection interface" width="2848" height="2026" data-path="images/dns-monitors/scheduling.png" />

  <img className="hidden dark:block" src="https://mintcdn.com/checkly-422f444a/Y_M8E0tne2AGh-nm/images/dns-monitors/scheduling-dark.png?fit=max&auto=format&n=Y_M8E0tne2AGh-nm&q=85&s=a0c728231628204f092e4fbe4f85ff08" alt="DNS monitor scheduling strategy and location selection interface" width="2848" height="2026" data-path="images/dns-monitors/scheduling-dark.png" />
</Frame>

* **Strategy:** Choose between round-robin or parallel execution. Learn more about [scheduling strategies](/concepts/scheduling)
* **Locations:** Select [public](/concepts/locations/#public-locations) or [private](/platform/private-locations/overview) locations to run the monitor from

### Additional Settings

* **Name:** Give your monitor a clear name to identify it in dashboards and alerts
* **Description:** Add context about what this monitor does and why it matters. Supports markdown, max 500 characters. When a failure occurs, [Rocky AI](/ai/rocky-ai) uses the description to provide more accurate [root cause and user impact analysis](/resolve/ai-root-cause-analysis/overview)
* **Tags:** Use tags to organize monitors across [dashboards](/communicate/dashboards/overview/) and [maintenance windows](/communicate/maintenance-windows/overview)
* **Retries:** Define how failed runs should be retried. See [retry strategies](/communicate/alerts/retries)
* **Alerting:** Configure your [alert settings](/communicate/alerts/configuration), [alert channels](/communicate/alerts/channels), or set up [webhooks](/integrations/alerts/webhooks) for custom integrations

## Common Use Cases

<Accordion title="Monitor CDN failover with multiple A records">
  **Scenario**: Your CDN provides multiple IP addresses for redundancy. You need to ensure all IPs are reachable.

  **Configuration**:

  * **Domain**: `cdn.example.com`
  * **Record type**: A
  * **Assertions**:
    * `$.Answer[0].TTL` is less than `300` (ensure low TTL for quick failover)
    * `$.Answer[0].data` equals expected IP address
    * Text response contains expected IP range (check multiple IPs in raw response)
</Accordion>

<Accordion title="Verify email security records (SPF, DKIM, DMARC)">
  **Scenario**: Monitor SPF, DKIM, and DMARC records to prevent email spoofing.

  **Configuration**:

  * **Domain**: `example.com`
  * **Record type**: TXT
  * **Assertions**:
    * Text response contains `v=spf1`
    * `$.Answer[0].data` contains `v=spf1`

  For DMARC:

  * **Domain**: `_dmarc.example.com`
  * **Record type**: TXT
  * **Assertions**:
    * Text response contains `v=DMARC1`
    * `$.Answer[0].data` contains `p=reject` or `p=quarantine`
</Accordion>

<Accordion title="Monitor mail server configuration">
  **Scenario**: Ensure primary and backup mail servers are correctly configured.

  **Configuration**:

  * **Domain**: `example.com`
  * **Record type**: MX
  * **Assertions**:
    * `$.Answer[0].data` contains `10 mail.example.com.` (priority 10 + hostname)
    * Text response contains `mail.example.com`
</Accordion>

<Accordion title="Test DNS propagation after zone transfer">
  **Scenario**: After updating nameservers, verify all nameservers return consistent results.

  **Configuration**:

  * **Domain**: `example.com`
  * **Record type**: NS
  * Create separate monitors for each nameserver:
    * Monitor 1: DNS server `ns1.example.com:53`
    * Monitor 2: DNS server `ns2.example.com:53`
  * **Assertions**:
    * `$.Answer[0].data` equals `ns1.example.com.` or `ns2.example.com.`
</Accordion>