Red Hat Knowledgebase

The official policy for HTTP is:

2** - Success
3** - Redirection
4** - Client Error
5** - Server Error

Accordingly, response codes in the range from 300 to 399 are treated by following the ('GET') redirect to an eventual non-3** response. The eventual response is then evaluated based on the following two rules:

1. Response codes in the range from 200 to 299 represent a "success" response from the server and are accordingly associated with an "OK" status. The configured checks are then applied to determine the final outcome of the check.
2. Response codes greater than or equal to 400 represent an "error" response from the server and are accordingly associated with a "Critical" status. No further checks are applied.