If it's a custom MVC site I'm assuming those settings/properties won't work as you'd expect. I'd create a page type called Link. Add the properties; link name (system), link text, link URL. In your controller handle whether or not it's internal or external by checking the link URL property, then perform a local or external redirect. We use this on v13 sites without issue.
if (Url.IsLocalUrl(link.LinkURL))
{
return LocalRedirect(link.LinkURL);
}
else
{
return RedirectPermanent(link.LinkURL);
}