session problem

[eluser]Unknown[/eluser]
I have a site: http://my.host.com
I have a domain: mydomain.com

My registrar set url forwarding mydomain.com -> my.host.com

I set config.php:

Code:

...
$config['base_url'] = "http://mydomain.com/";
...

so the session isn't working.

If I set config.php:

Code:

...
$config['base_url'] = "http://my.host.com/";
...

the session is working.

I think, have to set $config['cookie_prefix'], $config['cookie_domain'] and $config['cookie_path'] , but I don't how to?

ioros