Symfony - default_locale - Route without locale?

Question

symfony

I'm trying to figure it out, it always looks familiar after other frameworks
How to make a route in which you can not specify the language, but you can specify from a certain list?
I understand about _locale and defaults: _locale : en|ru|es
And if you need a route that would work without a language and redirect to the language - is it that there will be two identical actions or a pseudo-action with a forward?