Howtoforge posted a guide about installing a multiserver setup with dedicated Web, Email, DNS and MySQL Database Servers on Debian 5.0 with ISPConfig 3

This tutorial describes the installation of an ISPConfig 3 multiserver setup with dedicated web, email, database and two DNS servers all managed trough a single ISPConfig 3 control panel. The setup described below uses five servers and can be extended easily to to a higher number of servers by just adding more servers. E.g. if you want to have two mailservers, do the setup steps from chapter 2 on both of these servers. If you want to set up more web servers, then install ISPConfig on all other web servers in expert mode except of the first one.

  Installing A Multiserver Setup With Dedicated Web, Email, DNS And MySQL Database Servers On Debian 5.0 With ISPConfig 3