Hi forum, I have a ispconfig 3 server based on Debian Jessie. Server is set up using the "The Perfect Server - Debian 8.4 Jessie (Apache2, BIND, Dovecot, ISPConfig 3.1)" guide. There are just a view vhosts set up - but one has around 1500 alias domains defined. Server hardware is Intel Xeon E5-1650 v2 Hexa Core 64 GB DDR3 ECC 2× 240 GB SATA3 Data Center Series SSD The website uses Drupal (a PHP based CMS) to provide content in a mult-domain setup. Everything seems to be fine - but after some time the websites can not be reached anymore. And - the real cracy thing: the server load is really low (AVG < 1 + RAM still available and not swapping). So it seems, that there must be a limit in the number of connections or a internal configuration problem. But I can't find the problem ;-( I set up the website (with the 1500 alias domains) to use Fast-CGI. I already tried to increase the MaxRequestsPerProcess 2000 And to set mysql max_connectons + max_user_connections also to 2000 How can I find out where the real problem is? How to setup the vhost in ISPconfig best for such a lot of alias domains? I am happy for all suggestions!!