Site visitors constantly receive an error page when accessing the site
Your event log is showing “server is unreachable”
Site visitors experience intermittent connectivity issues
Upon completion of the DNS changes, as outlined by Incapsula, you are effectively directing all of your traffic via Incapsula’s network of proxy servers (Incapsula proxies). Incapsula proxies access your servers directly, and then serve content to the site visitors. Requests to your servers are therefore all coming from a limited range of Incapsula IP addresses. This may result in being classified as attack traffic by various traffic limiting mechanisms and denying Incapsula from accessing your servers.
Possible root cause:
Incapsula’s proxies are unable to connect to your servers.
There is a firewall or rate limiting mechanism that is blocking access to your servers.
There is a software package installed on your servers that is restricting access (for example: Apache servers have various modules that block requests: mod_deflate, mod_cband, mod_throttle, mod_bwlimited as well as others. The modules are intended to protect the server from high flow of traffic from a single source.