Zend路由器，在单个模块的URL中省略控制器

I have a module based Zend application.

One of my modules, called portfolio has only one controller, called index. For this single module, I'd like my route to look like this:

$route = new Zend_Controller_Router_Route('portfolio/:action',
                                          array(
                                                'module'        => 'portfolio',
                                                'controller'    => 'index',
                                                'action'        => 'index'
                                               )
                                         );

This works but messes up all links generated through Zend_Navigation.

Can this routing behavior be achieved, without messing up Zend_Navigation? (i.e. only inbound links are routed through this route. Outbound links are generated with the default route)

I can't use mod_rewrite.