I registered a route:
routes.MapRoute(
    "Journals",
    "Journals/{year}/{month}/{id}",
    new {
        controller = "Journals",
        action = "Get",
        year = UrlParameter.Optional,
        month = UrlParameter.Optional,
        id = UrlParameter.Optional
    }
);
Action:
public ActionResult Get(int? year, int? month, int? id)
Later in view (just to check):
@Url.Action("Get", "Journals")
@Url.Action("Get", "Journals", new { year = 2013 })
@Url.Action("Get", "Journals", new { year = 2013, month = 4 })
@Url.Action("Get", "Journals", new { year = 2013, month = 4, id = 1 })
And result is:
/Journals
/Journals
/Journals/2013/4
/Journals/2013/4/1
So the 2nd URL missed the parameter. What's wrong?