Conversion Goals in Google Analytics

I want to track my visitors who are entering my web site's main page (example.com) and then proceeding to forums.example.com. Is it possible?

As far as I understand I have to write /index.php for example.com and /index.php for forums.example.com which seems silly.

And can Google Analytic understand that forums.example.com/index.php and forums.example.com are same pages?

 

yes, this is absolutely possible with google analytic. see their help for more info