如何将MVC AREA中的某一个页设为起始页

public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Member", action = "Index", id = UrlParameter.Optional },
                namespaces:new string[] { "Gym.Mobile.Web.MemberUser.Controllers" }
            ).DataTokens.Add("Area", "MemberUser"); ;
        }
    }