In Rails 4 and above
get '/stories', to: redirect('/posts')
In case you need a named route, you may want to add an explicit as parameter:
get '/stories', to: redirect('/posts'), as: :however_you_want_to_name_it
Source: Redirection @ guides.rubyonrails.org
In Rails 3, you can redirect inside the routes.rb file.
match "/posts/github" => redirect("http://github.com/rails.atom")