Howtoforge published a tutorial about setting up a multiserver setup with the ISPConfig webhosting control panel on Ubuntu 20.04 and Debian 10.

ISPConfig Perfect Multiserver setup on Ubuntu 20.04 and Debian 10

This tutorial will take you through installing your own ISPConfig 3 multiserver setup with dedicated servers for the panel, web, DNS, mail, and webmail. Both the DNS and mail server will have a mirror server for redundancy. You can easily add more servers of a certain type afterwards.

ISPConfig's official auto-installer will be used to set up the servers. Debian 10 will be used as operating system. The guide has been tested with Ubuntu 20.04.2 as well.

ISPConfig Perfect Multiserver setup on Ubuntu 20.04 and Debian 10