installer does not expect ISPConfig Port to be 80 or 443
In a multi server setup, you could choose to have a dedicated ispconfig control panel server. When choosing port 80 or 443 as ISPConfig Port, it conflicts with the default apache config:
Starting httpd: (98)Address already in use: make_sock: could not bind to address [::]:80 (98)Address already in use: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down
Starting httpd: (98)Address already in use: make_sock: could not bind to address [::]:443 (98)Address already in use: make_sock: could not bind to address 0.0.0.0:443 no listening sockets available, shutting down
I need to uncomment the "Listen 80" or "Listen 443" in /etc/httpd/conf/sites-available/ispconfig.vhost to make apache start again.