Concepts Checks DNS

DNS Check

The DNS check resolves a hostname and verifies the result. Use it to confirm your domain points to the right address, or to detect DNS propagation issues across multiple nameservers.

Source: DnsCheckExecutor.cs · DnsCheckData.cs

What it verifies

• The hostname resolves without errors
• Optionally, the resolved value matches what you expect (IP, CNAME target)
• Optionally, resolution across multiple nameservers (partial failures → DEGRADED)

Common use cases

Basic resolution check

{ "host": "api.example.com", "recordType": "A" }

Verify a specific IP

{
  "host": "api.example.com",
  "recordType": "A",
  "expectedValue": "203.0.113.10"
}

Check a CNAME target

{
  "host": "www.example.com",
  "recordType": "CNAME",
  "expectedValue": "example.com"
}

Multi-nameserver check — DEGRADED if 1 NS fails, DOWN if all fail

{
  "host": "api.example.com",
  "recordType": "A",
  "nameServers": ["8.8.8.8", "1.1.1.1", "9.9.9.9"],
  "degradedAfter": 1
}

Configuration

Field	Default	Description
host	—	Hostname to resolve (required)
recordType	A	Record type: A, AAAA, or CNAME
nameServers	system resolver	List of nameserver IPs to query; empty = use system DNS
expectedValue	—	Expected resolved value; empty = any successful resolution
degradedAfter	1	Number of NS failures before going DEGRADED
downAfter	all NS	Number of NS failures before going DOWN
degradedLatencyMs	—	Resolution latency threshold for DEGRADED
downLatencyMs	—	Resolution latency threshold for DOWN

Statuses

Status	When
UP	Resolved successfully, value matches (if set)
DEGRADED	Some nameservers failed, or latency exceeded degradedLatencyMs
DOWN	All nameservers failed, value mismatch, or latency exceeded downLatencyMs
FAILURE	Host not configured, invalid record type, or invalid nameserver format

Latency

Measured per query. When multiple nameservers are used, the maximum latency across all is recorded.

Related

• Checks — common settings (schedule, thresholds, criticality)
• SSL Check — pair with DNS to also monitor the certificate on the resolved host