Routing in codeigniter

[eluser]Unknown[/eluser]
This is my code in routes.php

$route['default_controller'] = "admin";
$route['(:any)'] = $route['default_controller']."/index/";

This is my url:

http://myserver.net/visio/jklmn

But i cant to get the value in `index()` in `admin` controller.
I want to get the value `jklmn` in `admin` controller.If there is any mistake in my routing code.

This is my index() code;

function index($key = ""){
if(isset($key)){
$newkey = $key;
$data['key'] = $key;
$this->load->view('index',$data);
}else{
redirect('admin/index_login');
}

}


When i taking above link in browser i get the error message below:

Not Found

The requested URL /visio/jklmn was not found on this server.