Problem setting up Virtual Hosts

[Thomas]

Hi,

This problem is getting me crazy. I have a server in my office which I
use for tests. It has a dynamic address, and I chose DynDns to have a
domain name. So its domain name is of mysite.ath.cx. I have set in
dyndns control panel to have sub domains. The problem is that
mysite.ath.cx is accessible, but sub1.mysite.ath.cx (which point to
the same location as mysite.ath.cx) is not. What could possibly go
wrong? Is it dyndns playing with my nerves or a problem is my nginx
conf files?