I've setup Varnish as a reverse proxy on port 80 before Apache 2.2.22 + VirtualHosts on port 81.
When I enter my websites from port 81 it's all ok, then when I try to enter from port 80 I got Apache2 Test Page.
I'm running only one backend (all on the same machine).
What should I add to my Varnish config to support all Apache VirtualHosts ? I would like to have such universal rule that will add all new domains without having to change my Varnish config each time.
On Lighttpd + virtual hosts everything was running out of a box.
Check VirtualHost configuration, probably your vhost is configured only for *:81 but should be for *:80 too.