Cloudflare provides network and security services, primarily by acting as a reverse proxy between a user and a website’s server. Its global network speeds up web content by storing copies closer to users via a CDN (Content Delivery Network) and protects websites by filtering malicious traffic, like DDoS attacks. It also offers additional products for DNS, security, and web development.
Monitoring such services with Server Check can sometimes fail. This is usually because Cloudflare’s systems expect to see a browser, along with cookies, sessions, additional client-side scripts, etc., all of which are used to authenticate the browser and user visiting a website or other web-based service. By default, an automated system such as Server Check will probably be blocked because those additional resources are not provided as part of the monitoring request.
However, Server Check can be used successfully to monitor services that are protected behind Cloudflare’s systems. Within your Cloudflare dashboard, you should be able to configure a “white list” of hosts and IP addresses that are allowed to bypass the usual checks or authentication requirements. You can simply add your Server Check IP addresses to this list.
Cloudflare also offers DNS protection services which intercept DNS requests. In many cases, you can bypass this by using the actual IP addresses of your real servers (not Cloudflare’s IP addresses), instead of using the hostname/domain URL. The advantage of setting monitor testing to use an IP address instead of a hostname is that the test will continue to work even if the Cloudflare service fails.