Authentication between site and its virtual directory

[LV]

I have a site that uses FormsAuthentication. I have a virtual directory on this site, that is configured as a vitrual application and has it's own Web.config file in it. What I'm trying to achive: once a user is authenticated on to the "main" site, if he clicks a link redirecting to a page located in that virtual directory (i.e. from:

http://localhost/index.aspx

to

http://localhost/dir/index.aspx),

then the user is automatically authenticated into the directory as well. No success so far, Request.IsAuthenticated=false while on

http://localhost/dir/index.aspx

page, coming from

http://localhost/index.aspx.

<authentication mode="Forms"> in both Web.config in the root and directory and <identity impersonate="true" /> in /dir/Web.config. I thought that the cookies set by FormsAuthentication could be read on the same domain, am I missing some other settings? Any ideas or references will be appreciated. Thanks in advance!