Change default behavior for Unauthenticated users in Laravel 5.4

I want to change to where non-logged in user to be redirected when they try to access pages which required user to be logged in.

I have tried in Exceptions/Handler.php to change it like this

protected function unauthenticated($request, AuthenticationException $exception)
{
    if ($request->expectsJson()) {
        return response()->json(['error' => 'Unauthenticated.'], 401);
    }

    return redirect()->guest(route('/users/login'));
}

But when I try to access such page I've got error

InvalidArgumentException Route [/users/login] not defined.

My route in web.php is

Route::get ('/users/login', ['uses' => 'UsersController@getLoginPage', 'before' => 'guest']);

It's also same if I put the home /

Route [/] not defined.

Is this the correct place where this should be done?

via Chebli Mohamed