[Zope] ZSession (Newbie-)question

[Simon Brun]

hi

On my zope-site, I have a logging form. After a user logged in successfuly, a
session (with ZSession) with the item "user_id" is set. 

If he wants to post a comment to a news article for example, there is a check if
he have an active session or not. When he is logged in he can post. If he is not
logged in, he have to login first. This works just fine...

But, when a logged in user surfs to a subdomain (e.g. forums.mydomain.com) the
check failes and the user have to login another time. A new session will be
created...

How can I create a session for the hole site? Not for every subdomain?

thx for helping a newbie ;)
Simon