MVC :: Asp.Net Routing With Subdomain?

I am using MVC 2.0 to create my application,my problem i s related to the routing. Actually in my application each user have required seperate subdomain,like

www.example.com/user1/ ,www.example.com/user2/ ...etc.the default domain is www.example.com.So how can i make it possible with routing in mvc.

i have tried like this,
routes.Add(new Route("{id}", new RouteValueDictionary(new { controller = "User", action = "login", id = " " }), new MvcRouteHandler()));
var defaults = new RouteValueDictionary(
new
{
controller = "Home",
action = "Index",
id = UrlParameter.Optional
}
);
routes.Add(new Route("{controller}/{action}/{id}", defaults, new MvcRouteHandler()));

But the problem is that it take deafult (www.example.com) directly to user login page.I want the default page as Home/index and when www.example.com/user1/ it will go to user login page.