I just spend a while trying to figure this out - the documentation in routing.rb is out of date. A route like:
map.connect ':controller/:action/:id', :action => 'show', :defaults => { :page => 'Dashboard' }
will blow up with an error. (`assign_route_options': page: No matching segment exists; cannot assign default (ArgumentError)).
Turns out, after digging around, that the correct way to do this is now:
map.connect ':controller/:action/:id', :action => 'show', :page => 'Dashboard'