I have this IIS7.5 with ARR installed and configured to reverse proxy to another server which is running IIS7. On that IIS7.5 I have applications and simple websites installed. Since configuring a farm, the local application doesn't run with this error message: 502 - Web server received an invalid response while acting as a gateway or proxy server. There is a problem with the page you are looking for, and it cannot be displayed. When the Web server (while acting as a gateway or proxy) contacted the upstream content server, it received an invalid response from the content server. Is it even possible to run both application and routing (reverse proxy) at the same time?