WordPress MU

I have wpmu installed at http://domain.tld
When I visit http://sub1.domain.tld/wp-signup.php and signs up for sub2 domain, it gives me blog at following URL: http://sub2.sub1.domain.tld
Is it feature, or a bug? If it's a feature, how do I turn it off?

Something is up with your system, because on a recent install, if someone *does* go to http://sub1.domain.tld/wp-signup.php , they shoudl be redirected to the main signup page. Visitors should *NOT* be able to sign up to the site from a sub-blog.

Besides, they should not be able to get to a link like http://sub1.domain.tld/wp-signup.php unless it's on the page (which it shouldn't be), or they know the signup filename and typed it in.

Are you running the absolute latest? 1.3.2? I tested my version before that, so if someone can check a 1.3.2 install for this, we'll file a ticket.