Subdomains with Apache 2.2

I'm trying to set up a Apache 2.2 to work with subdomains. I've got a domain example.de which correctly points to the IP, my site www.example.com works. Now I want a bugtracker under bugzilla.example.com. All I did was to add a vHost with Servername bugzilla.example.com, but that does not work - the error message i开发者_开发问答s "Firefox can't find the server at bugzilla.example.com.". Why is that? example.com should point to the correct IP?

If you did only add the vhost the most probable problem is that you didnt add the Subdomain to your DNS - Zonefile.