DNS Resolution

The DNS Resolution check resolves hostnames through the device's resolver, the same way other programs on the device do. It reports when a name cannot be resolved, a lookup takes too long, or an expected IP address is missing. The check runs on the device with the octoja agent on Windows, Linux, and macOS (each in x64 and Arm64 builds), every 5 minutes by default.

Steps

1. Open the device.
2. Choose Checks → Add Check → DNS Resolution.
3. Enter the names to resolve under Hostnames and adjust the other fields if needed.

To cover several devices, assign the check with a config package.

Settings

Thresholds

• Expected address (optional) applies to every hostname in the check. The address is compared as a complete IP address, not as a substring. If you need different expected addresses, create one check per address.
• If Warning lookup time (ms) is greater than Error lookup time (ms), the check swaps the two values before evaluation.
• Up to ten hostnames are resolved at the same time. Blank entries are ignored, and leading and trailing spaces are removed.

Results

Every hostname is graded on its own. The check reports the worst result across all hostnames.

A missing expected address is evaluated before the lookup time: such a hostname is Critical even if it resolved quickly.

Per hostname, the check reports:

• Whether the name resolved
• Up to eight distinct returned addresses
• The lookup time in milliseconds
• Whether the expected address was found, if one is configured
• The result and, where one applies, the reason

The expected-address comparison considers every returned address, even though only the first eight are shown.

Notes

The check uses the operating system's resolver and therefore the device's DNS settings. It shows whether names resolve on this device. To query a specific DNS server or a specific record type such as MX or TXT, use the NSLookup check.

See also: Set up alerts for a check