I'm having these same issues.
This is a headless test system which I'm remotely admining. Currently there are no DNS-A records pointing to this machine because I'm planing to move my clients domains to this server if all goes well with ispconfig3.
I have 2 clients and each has its own test
domain set up.
The hostname of the machine is ie. hostname.com so I want to set up subdomains for testing
client 1 has client1.hostname.com
client 2 has client2.hostname.com
so I checked the sites-available directory and the doc roots are all ok:
client1: --> DocumentRoot /srv/www/client1.hostname.com/web
client2: --> DocumentRoot /srv/www/client2.hostname.com/web
but it still resolves to the first client1 directory and no matter what I type.
still shows the content from client1 this is frustrating. It is ignoring what i put as documentroot and only resolving the last client that i set up.
Is there some way to test this without having real domains attached to this machine? What I want to do is have all my clients set up with content and fake domains and when I'm ready just move the domain records to my new machine and then just change the domain settings in ispconfig3.