Real Client IPs
Running Varnish Cache as a reverse HTTP proxy in front of your normal web server leads to a logical problem: Since Varnish Cache is what actually connects to the backend on behalf of a website visitor, how will the backend determine the visitor's IP address?
This is a crucial problem. If the backend doesn't know your visitors' real IP addresses it will lead to unexpected behavior on your websites. Apache .htaccess Allow or Deny rules will fail, PHP scripts relying on IP addresses for sessions will log users out, website access logs will report wrong IPs... to name a few.
Please get in touch with our support department if you're stuck on anything. We're also happy to help if you'd like guidance for an alternative backend we haven't discussed here.