how to redirect the portal Logon page..IMP

Hi Frndz..

I want to know how i can change the Portal default logon page, means when ur giving url on browser like

http://host:port/irj/portal it will directs us to default portal logon page that we r familiar.

As per my requirement when we call the url ( http://host:port/irj/portal) it should call a custom JSP(fancy screen with AJAX&XML) page that i made , from this page i need to access portal .

So i want to use this custom JSP page as my portal logon page .

Thanks in Advance

Regards

Rajesh